[java] Intro openApiNullable property to enable/disable OpenAPI Jackson Nullable library (#6154)

* Add option to prevent usage of jackson-nullable (#2901)

Add a option for all java client and server to prevent
usage of third party library (jackson-databind-nullable)
which may be forbidden in some company

Add samples for Vertx, Spring MVC, Spring Cloud, Feign and Play

Upgrade dependencies for org.openapitools:jackson-databind-nullable

* Samples - Remove dependency org.openapitools:jackson-databind-nullable (#2901)

* Fix generation of gradle file for vertx (#2901)

* Regenerate samples (#2901)

* Fix documentation and up to date (#2901)

* Fix forgotten regeneration of vertx after dependency integration (#2901)

* Regenerate template after rebase (#2901)

* Use yaml config files introduce in #6509 to manage samples (#2901)

* Regenerate template using the config (#2901)

* Fix bad version during testing generated samples (#2901)

* Regenerate template after fix bad version (#2901)

* Fix merge, allow for set importing on codegen model

Co-authored-by: Jim Schubert <james.schubert@gmail.com>

samples/client/petstore/java/feign-no-nullable/src/main/AndroidManifest.xml

@@ -0,0 +1,3 @@
+<manifest package="org.openapitools.client" xmlns:android="http://schemas.android.com/apk/res/android">
+    <application />
+</manifest>

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/ApiClient.java

@@ -0,0 +1,352 @@
+package org.openapitools.client;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import org.apache.oltu.oauth2.client.request.OAuthClientRequest.AuthenticationRequestBuilder;
+import org.apache.oltu.oauth2.client.request.OAuthClientRequest.TokenRequestBuilder;
+
+import org.threeten.bp.*;
+
+import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import com.fasterxml.jackson.datatype.threetenbp.ThreeTenModule;
+
+import feign.Feign;
+import feign.RequestInterceptor;
+import feign.form.FormEncoder;
+import feign.jackson.JacksonDecoder;
+import feign.jackson.JacksonEncoder;
+import feign.slf4j.Slf4jLogger;
+import org.openapitools.client.auth.*;
+import org.openapitools.client.auth.OAuth.AccessTokenListener;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class ApiClient {
+  public interface Api {}
+
+  protected ObjectMapper objectMapper;
+  private String basePath = "http://petstore.swagger.io:80/v2";
+  private Map<String, RequestInterceptor> apiAuthorizations;
+  private Feign.Builder feignBuilder;
+
+  public ApiClient() {
+    objectMapper = createObjectMapper();
+    apiAuthorizations = new LinkedHashMap<String, RequestInterceptor>();
+    feignBuilder = Feign.builder()
+                .encoder(new FormEncoder(new JacksonEncoder(objectMapper)))
+                .decoder(new JacksonDecoder(objectMapper))
+                .logger(new Slf4jLogger());
+  }
+
+  public ApiClient(String[] authNames) {
+    this();
+    for(String authName : authNames) {
+      RequestInterceptor auth;
+      if ("api_key".equals(authName)) {
+        auth = new ApiKeyAuth("header", "api_key");
+      } else if ("api_key_query".equals(authName)) {
+        auth = new ApiKeyAuth("query", "api_key_query");
+      } else if ("http_basic_test".equals(authName)) {
+        auth = new HttpBasicAuth();
+      } else if ("petstore_auth".equals(authName)) {
+        auth = new OAuth(OAuthFlow.implicit, "http://petstore.swagger.io/api/oauth/dialog", "", "write:pets, read:pets");
+      } else {
+        throw new RuntimeException("auth name \"" + authName + "\" not found in available auth names");
+      }
+      addAuthorization(authName, auth);
+    }
+  }
+
+  /**
+   * Basic constructor for single auth name
+   * @param authName
+   */
+  public ApiClient(String authName) {
+    this(new String[]{authName});
+  }
+
+  /**
+   * Helper constructor for single api key
+   * @param authName
+   * @param apiKey
+   */
+  public ApiClient(String authName, String apiKey) {
+    this(authName);
+    this.setApiKey(apiKey);
+  }
+
+  /**
+   * Helper constructor for single basic auth or password oauth2
+   * @param authName
+   * @param username
+   * @param password
+   */
+  public ApiClient(String authName, String username, String password) {
+    this(authName);
+    this.setCredentials(username,  password);
+  }
+
+  /**
+   * Helper constructor for single password oauth2
+   * @param authName
+   * @param clientId
+   * @param secret
+   * @param username
+   * @param password
+   */
+  public ApiClient(String authName, String clientId, String secret, String username, String password) {
+    this(authName);
+    this.getTokenEndPoint()
+           .setClientId(clientId)
+           .setClientSecret(secret)
+           .setUsername(username)
+           .setPassword(password);
+  }
+
+  public String getBasePath() {
+    return basePath;
+  }
+
+  public ApiClient setBasePath(String basePath) {
+    this.basePath = basePath;
+    return this;
+  }
+
+  public Map<String, RequestInterceptor> getApiAuthorizations() {
+    return apiAuthorizations;
+  }
+
+  public void setApiAuthorizations(Map<String, RequestInterceptor> apiAuthorizations) {
+    this.apiAuthorizations = apiAuthorizations;
+  }
+
+  public Feign.Builder getFeignBuilder() {
+    return feignBuilder;
+  }
+
+  public ApiClient setFeignBuilder(Feign.Builder feignBuilder) {
+    this.feignBuilder = feignBuilder;
+    return this;
+  }
+
+  private ObjectMapper createObjectMapper() {
+    ObjectMapper objectMapper = new ObjectMapper();
+    objectMapper.enable(SerializationFeature.WRITE_ENUMS_USING_TO_STRING);
+    objectMapper.enable(DeserializationFeature.READ_ENUMS_USING_TO_STRING);
+    objectMapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
+    objectMapper.disable(DeserializationFeature.FAIL_ON_INVALID_SUBTYPE);
+    objectMapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
+    objectMapper.setDateFormat(new RFC3339DateFormat());
+    ThreeTenModule module = new ThreeTenModule();
+    module.addDeserializer(Instant.class, CustomInstantDeserializer.INSTANT);
+    module.addDeserializer(OffsetDateTime.class, CustomInstantDeserializer.OFFSET_DATE_TIME);
+    module.addDeserializer(ZonedDateTime.class, CustomInstantDeserializer.ZONED_DATE_TIME);
+    objectMapper.registerModule(module);
+    return objectMapper;
+  }
+
+  public ObjectMapper getObjectMapper(){
+    return objectMapper;
+  }
+
+  /**
+   * Creates a feign client for given API interface.
+   *
+   * Usage:
+   *    ApiClient apiClient = new ApiClient();
+   *    apiClient.setBasePath("http://localhost:8080");
+   *    XYZApi api = apiClient.buildClient(XYZApi.class);
+   *    XYZResponse response = api.someMethod(...);
+   * @param <T> Type
+   * @param clientClass Client class
+   * @return The Client
+   */
+  public <T extends Api> T buildClient(Class<T> clientClass) {
+    return feignBuilder.target(clientClass, basePath);
+  }
+
+  /**
+   * Select the Accept header's value from the given accepts array:
+   *   if JSON exists in the given array, use it;
+   *   otherwise use all of them (joining into a string)
+   *
+   * @param accepts The accepts array to select from
+   * @return The Accept header to use. If the given array is empty,
+   *   null will be returned (not to set the Accept header explicitly).
+   */
+  public String selectHeaderAccept(String[] accepts) {
+    if (accepts.length == 0) return null;
+    if (StringUtil.containsIgnoreCase(accepts, "application/json")) return "application/json";
+    return StringUtil.join(accepts, ",");
+  }
+
+  /**
+   * Select the Content-Type header's value from the given array:
+   *   if JSON exists in the given array, use it;
+   *   otherwise use the first one of the array.
+   *
+   * @param contentTypes The Content-Type array to select from
+   * @return The Content-Type header to use. If the given array is empty,
+   *   JSON will be used.
+   */
+  public String selectHeaderContentType(String[] contentTypes) {
+    if (contentTypes.length == 0) return "application/json";
+    if (StringUtil.containsIgnoreCase(contentTypes, "application/json")) return "application/json";
+    return contentTypes[0];
+  }
+
+
+  /**
+   * Helper method to configure the bearer token.
+   * @param bearerToken the bearer token.
+   */
+  public void setBearerToken(String bearerToken) {
+    for(RequestInterceptor apiAuthorization : apiAuthorizations.values()) {
+      if (apiAuthorization instanceof HttpBearerAuth) {
+        ((HttpBearerAuth) apiAuthorization).setBearerToken(bearerToken);
+        return;
+      }
+    }
+    throw new RuntimeException("No Bearer authentication configured!");
+  }
+
+  /**
+   * Helper method to configure the first api key found
+   * @param apiKey API key
+   */
+  public void setApiKey(String apiKey) {
+    for(RequestInterceptor apiAuthorization : apiAuthorizations.values()) {
+      if (apiAuthorization instanceof ApiKeyAuth) {
+        ApiKeyAuth keyAuth = (ApiKeyAuth) apiAuthorization;
+        keyAuth.setApiKey(apiKey);
+        return ;
+      }
+    }
+    throw new RuntimeException("No API key authentication configured!");
+  }
+
+  /**
+   * Helper method to configure the username/password for basic auth or password OAuth
+   * @param username Username
+   * @param password Password
+   */
+  public void setCredentials(String username, String password) {
+    for(RequestInterceptor apiAuthorization : apiAuthorizations.values()) {
+      if (apiAuthorization instanceof HttpBasicAuth) {
+        HttpBasicAuth basicAuth = (HttpBasicAuth) apiAuthorization;
+        basicAuth.setCredentials(username, password);
+        return;
+      }
+      if (apiAuthorization instanceof OAuth) {
+        OAuth oauth = (OAuth) apiAuthorization;
+        oauth.getTokenRequestBuilder().setUsername(username).setPassword(password);
+        return;
+      }
+    }
+    throw new RuntimeException("No Basic authentication or OAuth configured!");
+  }
+
+  /**
+   * Helper method to configure the token endpoint of the first oauth found in the apiAuthorizations (there should be only one)
+   * @return Token request builder
+   */
+  public TokenRequestBuilder getTokenEndPoint() {
+    for(RequestInterceptor apiAuthorization : apiAuthorizations.values()) {
+      if (apiAuthorization instanceof OAuth) {
+        OAuth oauth = (OAuth) apiAuthorization;
+        return oauth.getTokenRequestBuilder();
+      }
+    }
+    return null;
+  }
+
+  /**
+   * Helper method to configure authorization endpoint of the first oauth found in the apiAuthorizations (there should be only one)
+   * @return Authentication request builder
+   */
+  public AuthenticationRequestBuilder getAuthorizationEndPoint() {
+    for(RequestInterceptor apiAuthorization : apiAuthorizations.values()) {
+      if (apiAuthorization instanceof OAuth) {
+        OAuth oauth = (OAuth) apiAuthorization;
+        return oauth.getAuthenticationRequestBuilder();
+      }
+    }
+    return null;
+  }
+
+  /**
+   * Helper method to pre-set the oauth access token of the first oauth found in the apiAuthorizations (there should be only one)
+   * @param accessToken Access Token
+   * @param expiresIn Validity period in seconds
+   */
+  public void setAccessToken(String accessToken, Long expiresIn) {
+    for(RequestInterceptor apiAuthorization : apiAuthorizations.values()) {
+      if (apiAuthorization instanceof OAuth) {
+        OAuth oauth = (OAuth) apiAuthorization;
+        oauth.setAccessToken(accessToken, expiresIn);
+        return;
+      }
+    }
+  }
+
+  /**
+   * Helper method to configure the oauth accessCode/implicit flow parameters
+   * @param clientId Client ID
+   * @param clientSecret Client secret
+   * @param redirectURI Redirect URI
+   */
+  public void configureAuthorizationFlow(String clientId, String clientSecret, String redirectURI) {
+    for(RequestInterceptor apiAuthorization : apiAuthorizations.values()) {
+      if (apiAuthorization instanceof OAuth) {
+        OAuth oauth = (OAuth) apiAuthorization;
+        oauth.getTokenRequestBuilder()
+                .setClientId(clientId)
+                .setClientSecret(clientSecret)
+                .setRedirectURI(redirectURI);
+        oauth.getAuthenticationRequestBuilder()
+                .setClientId(clientId)
+                .setRedirectURI(redirectURI);
+        return;
+      }
+    }
+  }
+
+  /**
+   * Configures a listener which is notified when a new access token is received.
+   * @param accessTokenListener Acesss token listener
+   */
+  public void registerAccessTokenListener(AccessTokenListener accessTokenListener) {
+    for(RequestInterceptor apiAuthorization : apiAuthorizations.values()) {
+      if (apiAuthorization instanceof OAuth) {
+        OAuth oauth = (OAuth) apiAuthorization;
+        oauth.registerAccessTokenListener(accessTokenListener);
+        return;
+      }
+    }
+  }
+
+  /**
+   * Gets request interceptor based on authentication name
+   * @param authName Authentiation name
+   * @return Request Interceptor
+   */
+  public RequestInterceptor getAuthorization(String authName) {
+    return apiAuthorizations.get(authName);
+  }
+
+  /**
+   * Adds an authorization to be used by the client
+   * @param authName Authentication name
+   * @param authorization Request interceptor
+   */
+  public void addAuthorization(String authName, RequestInterceptor authorization) {
+    if (apiAuthorizations.containsKey(authName)) {
+      throw new RuntimeException("auth name \"" + authName + "\" already in api authorizations");
+    }
+    apiAuthorizations.put(authName, authorization);
+    feignBuilder.requestInterceptor(authorization);
+  }
+
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/CustomInstantDeserializer.java

@@ -0,0 +1,232 @@
+package org.openapitools.client;
+
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.core.JsonTokenId;
+import com.fasterxml.jackson.databind.DeserializationContext;
+import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.JsonDeserializer;
+import com.fasterxml.jackson.datatype.threetenbp.DecimalUtils;
+import com.fasterxml.jackson.datatype.threetenbp.deser.ThreeTenDateTimeDeserializerBase;
+import com.fasterxml.jackson.datatype.threetenbp.function.BiFunction;
+import com.fasterxml.jackson.datatype.threetenbp.function.Function;
+import org.threeten.bp.DateTimeException;
+import org.threeten.bp.DateTimeUtils;
+import org.threeten.bp.Instant;
+import org.threeten.bp.OffsetDateTime;
+import org.threeten.bp.ZoneId;
+import org.threeten.bp.ZonedDateTime;
+import org.threeten.bp.format.DateTimeFormatter;
+import org.threeten.bp.temporal.Temporal;
+import org.threeten.bp.temporal.TemporalAccessor;
+
+import java.io.IOException;
+import java.math.BigDecimal;
+
+/**
+ * Deserializer for ThreeTen temporal {@link Instant}s, {@link OffsetDateTime}, and {@link ZonedDateTime}s.
+ * Adapted from the jackson threetenbp InstantDeserializer to add support for deserializing rfc822 format.
+ *
+ * @author Nick Williams
+ */
+public class CustomInstantDeserializer<T extends Temporal>
+    extends ThreeTenDateTimeDeserializerBase<T> {
+  private static final long serialVersionUID = 1L;
+
+  public static final CustomInstantDeserializer<Instant> INSTANT = new CustomInstantDeserializer<Instant>(
+      Instant.class, DateTimeFormatter.ISO_INSTANT,
+      new Function<TemporalAccessor, Instant>() {
+        @Override
+        public Instant apply(TemporalAccessor temporalAccessor) {
+          return Instant.from(temporalAccessor);
+        }
+      },
+      new Function<FromIntegerArguments, Instant>() {
+        @Override
+        public Instant apply(FromIntegerArguments a) {
+          return Instant.ofEpochMilli(a.value);
+        }
+      },
+      new Function<FromDecimalArguments, Instant>() {
+        @Override
+        public Instant apply(FromDecimalArguments a) {
+          return Instant.ofEpochSecond(a.integer, a.fraction);
+        }
+      },
+      null
+  );
+
+  public static final CustomInstantDeserializer<OffsetDateTime> OFFSET_DATE_TIME = new CustomInstantDeserializer<OffsetDateTime>(
+      OffsetDateTime.class, DateTimeFormatter.ISO_OFFSET_DATE_TIME,
+      new Function<TemporalAccessor, OffsetDateTime>() {
+        @Override
+        public OffsetDateTime apply(TemporalAccessor temporalAccessor) {
+          return OffsetDateTime.from(temporalAccessor);
+        }
+      },
+      new Function<FromIntegerArguments, OffsetDateTime>() {
+        @Override
+        public OffsetDateTime apply(FromIntegerArguments a) {
+          return OffsetDateTime.ofInstant(Instant.ofEpochMilli(a.value), a.zoneId);
+        }
+      },
+      new Function<FromDecimalArguments, OffsetDateTime>() {
+        @Override
+        public OffsetDateTime apply(FromDecimalArguments a) {
+          return OffsetDateTime.ofInstant(Instant.ofEpochSecond(a.integer, a.fraction), a.zoneId);
+        }
+      },
+      new BiFunction<OffsetDateTime, ZoneId, OffsetDateTime>() {
+        @Override
+        public OffsetDateTime apply(OffsetDateTime d, ZoneId z) {
+          return d.withOffsetSameInstant(z.getRules().getOffset(d.toLocalDateTime()));
+        }
+      }
+  );
+
+  public static final CustomInstantDeserializer<ZonedDateTime> ZONED_DATE_TIME = new CustomInstantDeserializer<ZonedDateTime>(
+      ZonedDateTime.class, DateTimeFormatter.ISO_ZONED_DATE_TIME,
+      new Function<TemporalAccessor, ZonedDateTime>() {
+        @Override
+        public ZonedDateTime apply(TemporalAccessor temporalAccessor) {
+          return ZonedDateTime.from(temporalAccessor);
+        }
+      },
+      new Function<FromIntegerArguments, ZonedDateTime>() {
+        @Override
+        public ZonedDateTime apply(FromIntegerArguments a) {
+          return ZonedDateTime.ofInstant(Instant.ofEpochMilli(a.value), a.zoneId);
+        }
+      },
+      new Function<FromDecimalArguments, ZonedDateTime>() {
+        @Override
+        public ZonedDateTime apply(FromDecimalArguments a) {
+          return ZonedDateTime.ofInstant(Instant.ofEpochSecond(a.integer, a.fraction), a.zoneId);
+        }
+      },
+      new BiFunction<ZonedDateTime, ZoneId, ZonedDateTime>() {
+        @Override
+        public ZonedDateTime apply(ZonedDateTime zonedDateTime, ZoneId zoneId) {
+          return zonedDateTime.withZoneSameInstant(zoneId);
+        }
+      }
+  );
+
+  protected final Function<FromIntegerArguments, T> fromMilliseconds;
+
+  protected final Function<FromDecimalArguments, T> fromNanoseconds;
+
+  protected final Function<TemporalAccessor, T> parsedToValue;
+
+  protected final BiFunction<T, ZoneId, T> adjust;
+
+  protected CustomInstantDeserializer(Class<T> supportedType,
+                    DateTimeFormatter parser,
+                    Function<TemporalAccessor, T> parsedToValue,
+                    Function<FromIntegerArguments, T> fromMilliseconds,
+                    Function<FromDecimalArguments, T> fromNanoseconds,
+                    BiFunction<T, ZoneId, T> adjust) {
+    super(supportedType, parser);
+    this.parsedToValue = parsedToValue;
+    this.fromMilliseconds = fromMilliseconds;
+    this.fromNanoseconds = fromNanoseconds;
+    this.adjust = adjust == null ? new BiFunction<T, ZoneId, T>() {
+      @Override
+      public T apply(T t, ZoneId zoneId) {
+        return t;
+      }
+    } : adjust;
+  }
+
+  @SuppressWarnings("unchecked")
+  protected CustomInstantDeserializer(CustomInstantDeserializer<T> base, DateTimeFormatter f) {
+    super((Class<T>) base.handledType(), f);
+    parsedToValue = base.parsedToValue;
+    fromMilliseconds = base.fromMilliseconds;
+    fromNanoseconds = base.fromNanoseconds;
+    adjust = base.adjust;
+  }
+
+  @Override
+  protected JsonDeserializer<T> withDateFormat(DateTimeFormatter dtf) {
+    if (dtf == _formatter) {
+      return this;
+    }
+    return new CustomInstantDeserializer<T>(this, dtf);
+  }
+
+  @Override
+  public T deserialize(JsonParser parser, DeserializationContext context) throws IOException {
+    //NOTE: Timestamps contain no timezone info, and are always in configured TZ. Only
+    //string values have to be adjusted to the configured TZ.
+    switch (parser.getCurrentTokenId()) {
+      case JsonTokenId.ID_NUMBER_FLOAT: {
+        BigDecimal value = parser.getDecimalValue();
+        long seconds = value.longValue();
+        int nanoseconds = DecimalUtils.extractNanosecondDecimal(value, seconds);
+        return fromNanoseconds.apply(new FromDecimalArguments(
+            seconds, nanoseconds, getZone(context)));
+      }
+
+      case JsonTokenId.ID_NUMBER_INT: {
+        long timestamp = parser.getLongValue();
+        if (context.isEnabled(DeserializationFeature.READ_DATE_TIMESTAMPS_AS_NANOSECONDS)) {
+          return this.fromNanoseconds.apply(new FromDecimalArguments(
+              timestamp, 0, this.getZone(context)
+          ));
+        }
+        return this.fromMilliseconds.apply(new FromIntegerArguments(
+            timestamp, this.getZone(context)
+        ));
+      }
+
+      case JsonTokenId.ID_STRING: {
+        String string = parser.getText().trim();
+        if (string.length() == 0) {
+          return null;
+        }
+        if (string.endsWith("+0000")) {
+          string = string.substring(0, string.length() - 5) + "Z";
+        }
+        T value;
+        try {
+          TemporalAccessor acc = _formatter.parse(string);
+          value = parsedToValue.apply(acc);
+          if (context.isEnabled(DeserializationFeature.ADJUST_DATES_TO_CONTEXT_TIME_ZONE)) {
+            return adjust.apply(value, this.getZone(context));
+          }
+        } catch (DateTimeException e) {
+          throw _peelDTE(e);
+        }
+        return value;
+      }
+    }
+    throw context.mappingException("Expected type float, integer, or string.");
+  }
+
+  private ZoneId getZone(DeserializationContext context) {
+    // Instants are always in UTC, so don't waste compute cycles
+    return (_valueClass == Instant.class) ? null : DateTimeUtils.toZoneId(context.getTimeZone());
+  }
+
+  private static class FromIntegerArguments {
+    public final long value;
+    public final ZoneId zoneId;
+
+    private FromIntegerArguments(long value, ZoneId zoneId) {
+      this.value = value;
+      this.zoneId = zoneId;
+    }
+  }
+
+  private static class FromDecimalArguments {
+    public final long integer;
+    public final int fraction;
+    public final ZoneId zoneId;
+
+    private FromDecimalArguments(long integer, int fraction, ZoneId zoneId) {
+      this.integer = integer;
+      this.fraction = fraction;
+      this.zoneId = zoneId;
+    }
+  }
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/EncodingUtils.java

@@ -0,0 +1,86 @@
+package org.openapitools.client;
+
+import java.io.UnsupportedEncodingException;
+import java.net.URLEncoder;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+/**
+* Utilities to support Swagger encoding formats in Feign.
+*/
+public final class EncodingUtils {
+
+  /**
+   * Private constructor. Do not construct this class.
+   */
+  private EncodingUtils() {}
+
+  /**
+   * <p>Encodes a collection of query parameters according to the Swagger
+   * collection format.</p>
+   *
+   * <p>Of the various collection formats defined by Swagger ("csv", "tsv",
+   * etc), Feign only natively supports "multi". This utility generates the
+   * other format types so it will be properly processed by Feign.</p>
+   *
+   * <p>Note, as part of reformatting, it URL encodes the parameters as
+   * well.</p>
+   * @param parameters The collection object to be formatted. This object will
+   *                   not be changed.
+   * @param collectionFormat The Swagger collection format (eg, "csv", "tsv",
+   *                         "pipes"). See the
+   *                         <a href="http://swagger.io/specification/#parameter-object-44">
+   *                         OpenAPI Spec</a> for more details.
+   * @return An object that will be correctly formatted by Feign.
+   */
+  public static Object encodeCollection(Collection<?> parameters,
+                                     String collectionFormat) {
+    if (parameters == null) {
+      return parameters;
+    }
+    List<String> stringValues = new ArrayList<>(parameters.size());
+    for (Object parameter : parameters) {
+      // ignore null values (same behavior as Feign)
+      if (parameter != null) {
+        stringValues.add(encode(parameter));
+      }
+    }
+    // Feign natively handles single-element lists and the "multi" format.
+    if (stringValues.size() < 2 || "multi".equals(collectionFormat)) {
+      return stringValues;
+    }
+    // Otherwise return a formatted String
+    String[] stringArray = stringValues.toArray(new String[0]);
+    switch (collectionFormat) {
+      case "csv":
+      default:
+        return StringUtil.join(stringArray, ",");
+      case "ssv":
+        return StringUtil.join(stringArray, " ");
+      case "tsv":
+        return StringUtil.join(stringArray, "\t");
+      case "pipes":
+        return StringUtil.join(stringArray, "|");
+    }
+  }
+
+  /**
+   * URL encode a single query parameter.
+   * @param parameter The query parameter to encode. This object will not be
+   *                  changed.
+   * @return The URL encoded string representation of the parameter. If the
+   *         parameter is null, returns null.
+   */
+  public static String encode(Object parameter) {
+    if (parameter == null) {
+      return null;
+    }
+    try {
+      return URLEncoder.encode(parameter.toString(), "UTF-8").replaceAll("\\+", "%20");
+    } catch (UnsupportedEncodingException e) {
+      // Should never happen, UTF-8 is always supported
+      throw new RuntimeException(e);
+    }
+  }
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/ParamExpander.java

@@ -0,0 +1,22 @@
+package org.openapitools.client;
+
+import feign.Param;
+
+import java.text.DateFormat;
+import java.util.Date;
+
+/**
+ * Param Expander to convert {@link Date} to RFC3339
+ */
+public class ParamExpander implements Param.Expander {
+
+  private static final DateFormat dateformat = new RFC3339DateFormat();
+
+  @Override
+  public String expand(Object value) {
+    if (value instanceof Date) {
+      return dateformat.format(value);
+    }
+    return value.toString();
+  }
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/RFC3339DateFormat.java

@@ -0,0 +1,55 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+package org.openapitools.client;
+
+import com.fasterxml.jackson.databind.util.StdDateFormat;
+
+import java.text.DateFormat;
+import java.text.FieldPosition;
+import java.text.ParsePosition;
+import java.util.Date;
+import java.util.GregorianCalendar;
+import java.util.TimeZone;
+
+public class RFC3339DateFormat extends DateFormat {
+  private static final long serialVersionUID = 1L;
+  private static final TimeZone TIMEZONE_Z = TimeZone.getTimeZone("UTC");
+
+  private final StdDateFormat fmt = new StdDateFormat()
+          .withTimeZone(TIMEZONE_Z)
+          .withColonInTimeZone(true);
+
+  public RFC3339DateFormat() {
+    this.calendar = new GregorianCalendar();
+  }
+
+  @Override
+  public Date parse(String source) {
+    return parse(source, new ParsePosition(0));
+  }
+
+  @Override
+  public Date parse(String source, ParsePosition pos) {
+    return fmt.parse(source, pos);
+  }
+
+  @Override
+  public StringBuffer format(Date date, StringBuffer toAppendTo, FieldPosition fieldPosition) {
+    return fmt.format(date, toAppendTo, fieldPosition);
+  }
+
+  @Override
+  public Object clone() {
+    return this;
+  }
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/StringUtil.java

@@ -0,0 +1,83 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client;
+
+import java.util.Collection;
+import java.util.Iterator;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class StringUtil {
+  /**
+   * Check if the given array contains the given value (with case-insensitive comparison).
+   *
+   * @param array The array
+   * @param value The value to search
+   * @return true if the array contains the value
+   */
+  public static boolean containsIgnoreCase(String[] array, String value) {
+    for (String str : array) {
+      if (value == null && str == null) {
+        return true;
+      }
+      if (value != null && value.equalsIgnoreCase(str)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  /**
+   * Join an array of strings with the given separator.
+   * <p>
+   * Note: This might be replaced by utility method from commons-lang or guava someday
+   * if one of those libraries is added as dependency.
+   * </p>
+   *
+   * @param array     The array of strings
+   * @param separator The separator
+   * @return the resulting string
+   */
+  public static String join(String[] array, String separator) {
+    int len = array.length;
+    if (len == 0) {
+      return "";
+    }
+
+    StringBuilder out = new StringBuilder();
+    out.append(array[0]);
+    for (int i = 1; i < len; i++) {
+      out.append(separator).append(array[i]);
+    }
+    return out.toString();
+  }
+
+  /**
+   * Join a list of strings with the given separator.
+   *
+   * @param list      The list of strings
+   * @param separator The separator
+   * @return the resulting string
+   */
+  public static String join(Collection<String> list, String separator) {
+    Iterator<String> iterator = list.iterator();
+    StringBuilder out = new StringBuilder();
+    if (iterator.hasNext()) {
+      out.append(iterator.next());
+    }
+    while (iterator.hasNext()) {
+      out.append(separator).append(iterator.next());
+    }
+    return out.toString();
+  }
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/api/AnotherFakeApi.java

@@ -0,0 +1,30 @@
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.EncodingUtils;
+
+import org.openapitools.client.model.Client;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import feign.*;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public interface AnotherFakeApi extends ApiClient.Api {
+
+
+  /**
+   * To test special tags
+   * To test special tags and operation ID starting with number
+   * @param body client model (required)
+   * @return Client
+   */
+  @RequestLine("PATCH /another-fake/dummy")
+  @Headers({
+    "Content-Type: application/json",
+    "Accept: application/json",
+  })
+  Client call123testSpecialTags(Client body);
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/api/FakeApi.java

@@ -0,0 +1,422 @@
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.EncodingUtils;
+
+import java.math.BigDecimal;
+import org.openapitools.client.model.Client;
+import java.io.File;
+import org.openapitools.client.model.FileSchemaTestClass;
+import org.threeten.bp.LocalDate;
+import org.threeten.bp.OffsetDateTime;
+import org.openapitools.client.model.OuterComposite;
+import org.openapitools.client.model.User;
+import org.openapitools.client.model.XmlItem;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import feign.*;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public interface FakeApi extends ApiClient.Api {
+
+
+  /**
+   * creates an XmlItem
+   * this route creates an XmlItem
+   * @param xmlItem XmlItem Body (required)
+   */
+  @RequestLine("POST /fake/create_xml_item")
+  @Headers({
+    "Content-Type: application/xml",
+    "Accept: application/json",
+  })
+  void createXmlItem(XmlItem xmlItem);
+
+  /**
+   * 
+   * Test serialization of outer boolean types
+   * @param body Input boolean as post body (optional)
+   * @return Boolean
+   */
+  @RequestLine("POST /fake/outer/boolean")
+  @Headers({
+    "Content-Type: */*",
+    "Accept: */*",
+  })
+  Boolean fakeOuterBooleanSerialize(Boolean body);
+
+  /**
+   * 
+   * Test serialization of object with outer number type
+   * @param body Input composite as post body (optional)
+   * @return OuterComposite
+   */
+  @RequestLine("POST /fake/outer/composite")
+  @Headers({
+    "Content-Type: */*",
+    "Accept: */*",
+  })
+  OuterComposite fakeOuterCompositeSerialize(OuterComposite body);
+
+  /**
+   * 
+   * Test serialization of outer number types
+   * @param body Input number as post body (optional)
+   * @return BigDecimal
+   */
+  @RequestLine("POST /fake/outer/number")
+  @Headers({
+    "Content-Type: */*",
+    "Accept: */*",
+  })
+  BigDecimal fakeOuterNumberSerialize(BigDecimal body);
+
+  /**
+   * 
+   * Test serialization of outer string types
+   * @param body Input string as post body (optional)
+   * @return String
+   */
+  @RequestLine("POST /fake/outer/string")
+  @Headers({
+    "Content-Type: */*",
+    "Accept: */*",
+  })
+  String fakeOuterStringSerialize(String body);
+
+  /**
+   * 
+   * For this test, the body for this request much reference a schema named `File`.
+   * @param body  (required)
+   */
+  @RequestLine("PUT /fake/body-with-file-schema")
+  @Headers({
+    "Content-Type: application/json",
+    "Accept: application/json",
+  })
+  void testBodyWithFileSchema(FileSchemaTestClass body);
+
+  /**
+   * 
+   * 
+   * @param query  (required)
+   * @param body  (required)
+   */
+  @RequestLine("PUT /fake/body-with-query-params?query={query}")
+  @Headers({
+    "Content-Type: application/json",
+    "Accept: application/json",
+  })
+  void testBodyWithQueryParams(@Param("query") String query, User body);
+
+  /**
+   * 
+   * 
+   * Note, this is equivalent to the other <code>testBodyWithQueryParams</code> method,
+   * but with the query parameters collected into a single Map parameter. This
+   * is convenient for services with optional query parameters, especially when
+   * used with the {@link TestBodyWithQueryParamsQueryParams} class that allows for
+   * building up this map in a fluent style.
+   * @param body  (required)
+   * @param queryParams Map of query parameters as name-value pairs
+   *   <p>The following elements may be specified in the query map:</p>
+   *   <ul>
+   *   <li>query -  (required)</li>
+   *   </ul>
+   */
+  @RequestLine("PUT /fake/body-with-query-params?query={query}")
+  @Headers({
+  "Content-Type: application/json",
+  "Accept: application/json",
+  })
+  void testBodyWithQueryParams(User body, @QueryMap(encoded=true) Map<String, Object> queryParams);
+
+  /**
+   * A convenience class for generating query parameters for the
+   * <code>testBodyWithQueryParams</code> method in a fluent style.
+   */
+  public static class TestBodyWithQueryParamsQueryParams extends HashMap<String, Object> {
+    public TestBodyWithQueryParamsQueryParams query(final String value) {
+      put("query", EncodingUtils.encode(value));
+      return this;
+    }
+  }
+
+  /**
+   * To test \&quot;client\&quot; model
+   * To test \&quot;client\&quot; model
+   * @param body client model (required)
+   * @return Client
+   */
+  @RequestLine("PATCH /fake")
+  @Headers({
+    "Content-Type: application/json",
+    "Accept: application/json",
+  })
+  Client testClientModel(Client body);
+
+  /**
+   * Fake endpoint for testing various parameters  假端點  偽のエンドポイント  가짜 엔드 포인트
+   * Fake endpoint for testing various parameters  假端點  偽のエンドポイント  가짜 엔드 포인트
+   * @param number None (required)
+   * @param _double None (required)
+   * @param patternWithoutDelimiter None (required)
+   * @param _byte None (required)
+   * @param integer None (optional)
+   * @param int32 None (optional)
+   * @param int64 None (optional)
+   * @param _float None (optional)
+   * @param string None (optional)
+   * @param binary None (optional)
+   * @param date None (optional)
+   * @param dateTime None (optional)
+   * @param password None (optional)
+   * @param paramCallback None (optional)
+   */
+  @RequestLine("POST /fake")
+  @Headers({
+    "Content-Type: application/x-www-form-urlencoded",
+    "Accept: application/json",
+  })
+  void testEndpointParameters(@Param("number") BigDecimal number, @Param("_double") Double _double, @Param("patternWithoutDelimiter") String patternWithoutDelimiter, @Param("_byte") byte[] _byte, @Param("integer") Integer integer, @Param("int32") Integer int32, @Param("int64") Long int64, @Param("_float") Float _float, @Param("string") String string, @Param("binary") File binary, @Param("date") LocalDate date, @Param("dateTime") OffsetDateTime dateTime, @Param("password") String password, @Param("paramCallback") String paramCallback);
+
+  /**
+   * To test enum parameters
+   * To test enum parameters
+   * @param enumHeaderStringArray Header parameter enum test (string array) (optional)
+   * @param enumHeaderString Header parameter enum test (string) (optional, default to -efg)
+   * @param enumQueryStringArray Query parameter enum test (string array) (optional)
+   * @param enumQueryString Query parameter enum test (string) (optional, default to -efg)
+   * @param enumQueryInteger Query parameter enum test (double) (optional)
+   * @param enumQueryDouble Query parameter enum test (double) (optional)
+   * @param enumFormStringArray Form parameter enum test (string array) (optional)
+   * @param enumFormString Form parameter enum test (string) (optional, default to -efg)
+   */
+  @RequestLine("GET /fake?enum_query_string_array={enumQueryStringArray}&enum_query_string={enumQueryString}&enum_query_integer={enumQueryInteger}&enum_query_double={enumQueryDouble}")
+  @Headers({
+    "Content-Type: application/x-www-form-urlencoded",
+    "Accept: application/json",
+    "enum_header_string_array: {enumHeaderStringArray}",
+    
+    "enum_header_string: {enumHeaderString}"
+  })
+  void testEnumParameters(@Param("enumHeaderStringArray") List<String> enumHeaderStringArray, @Param("enumHeaderString") String enumHeaderString, @Param("enumQueryStringArray") List<String> enumQueryStringArray, @Param("enumQueryString") String enumQueryString, @Param("enumQueryInteger") Integer enumQueryInteger, @Param("enumQueryDouble") Double enumQueryDouble, @Param("enumFormStringArray") List<String> enumFormStringArray, @Param("enumFormString") String enumFormString);
+
+  /**
+   * To test enum parameters
+   * To test enum parameters
+   * Note, this is equivalent to the other <code>testEnumParameters</code> method,
+   * but with the query parameters collected into a single Map parameter. This
+   * is convenient for services with optional query parameters, especially when
+   * used with the {@link TestEnumParametersQueryParams} class that allows for
+   * building up this map in a fluent style.
+   * @param enumHeaderStringArray Header parameter enum test (string array) (optional)
+   * @param enumHeaderString Header parameter enum test (string) (optional, default to -efg)
+   * @param enumFormStringArray Form parameter enum test (string array) (optional)
+   * @param enumFormString Form parameter enum test (string) (optional, default to -efg)
+   * @param queryParams Map of query parameters as name-value pairs
+   *   <p>The following elements may be specified in the query map:</p>
+   *   <ul>
+   *   <li>enumQueryStringArray - Query parameter enum test (string array) (optional)</li>
+   *   <li>enumQueryString - Query parameter enum test (string) (optional, default to -efg)</li>
+   *   <li>enumQueryInteger - Query parameter enum test (double) (optional)</li>
+   *   <li>enumQueryDouble - Query parameter enum test (double) (optional)</li>
+   *   </ul>
+   */
+  @RequestLine("GET /fake?enum_query_string_array={enumQueryStringArray}&enum_query_string={enumQueryString}&enum_query_integer={enumQueryInteger}&enum_query_double={enumQueryDouble}")
+  @Headers({
+  "Content-Type: application/x-www-form-urlencoded",
+  "Accept: application/json",
+      "enum_header_string_array: {enumHeaderStringArray}",
+      
+      "enum_header_string: {enumHeaderString}"
+  })
+  void testEnumParameters(@Param("enumHeaderStringArray") List<String> enumHeaderStringArray, @Param("enumHeaderString") String enumHeaderString, @Param("enumFormStringArray") List<String> enumFormStringArray, @Param("enumFormString") String enumFormString, @QueryMap(encoded=true) Map<String, Object> queryParams);
+
+  /**
+   * A convenience class for generating query parameters for the
+   * <code>testEnumParameters</code> method in a fluent style.
+   */
+  public static class TestEnumParametersQueryParams extends HashMap<String, Object> {
+    public TestEnumParametersQueryParams enumQueryStringArray(final List<String> value) {
+      put("enum_query_string_array", EncodingUtils.encodeCollection(value, "csv"));
+      return this;
+    }
+    public TestEnumParametersQueryParams enumQueryString(final String value) {
+      put("enum_query_string", EncodingUtils.encode(value));
+      return this;
+    }
+    public TestEnumParametersQueryParams enumQueryInteger(final Integer value) {
+      put("enum_query_integer", EncodingUtils.encode(value));
+      return this;
+    }
+    public TestEnumParametersQueryParams enumQueryDouble(final Double value) {
+      put("enum_query_double", EncodingUtils.encode(value));
+      return this;
+    }
+  }
+
+  /**
+   * Fake endpoint to test group parameters (optional)
+   * Fake endpoint to test group parameters (optional)
+   * @param requiredStringGroup Required String in group parameters (required)
+   * @param requiredBooleanGroup Required Boolean in group parameters (required)
+   * @param requiredInt64Group Required Integer in group parameters (required)
+   * @param stringGroup String in group parameters (optional)
+   * @param booleanGroup Boolean in group parameters (optional)
+   * @param int64Group Integer in group parameters (optional)
+   */
+  @RequestLine("DELETE /fake?required_string_group={requiredStringGroup}&required_int64_group={requiredInt64Group}&string_group={stringGroup}&int64_group={int64Group}")
+  @Headers({
+    "Accept: application/json",
+    "required_boolean_group: {requiredBooleanGroup}",
+    
+    "boolean_group: {booleanGroup}"
+  })
+  void testGroupParameters(@Param("requiredStringGroup") Integer requiredStringGroup, @Param("requiredBooleanGroup") Boolean requiredBooleanGroup, @Param("requiredInt64Group") Long requiredInt64Group, @Param("stringGroup") Integer stringGroup, @Param("booleanGroup") Boolean booleanGroup, @Param("int64Group") Long int64Group);
+
+  /**
+   * Fake endpoint to test group parameters (optional)
+   * Fake endpoint to test group parameters (optional)
+   * Note, this is equivalent to the other <code>testGroupParameters</code> method,
+   * but with the query parameters collected into a single Map parameter. This
+   * is convenient for services with optional query parameters, especially when
+   * used with the {@link TestGroupParametersQueryParams} class that allows for
+   * building up this map in a fluent style.
+   * @param requiredBooleanGroup Required Boolean in group parameters (required)
+   * @param booleanGroup Boolean in group parameters (optional)
+   * @param queryParams Map of query parameters as name-value pairs
+   *   <p>The following elements may be specified in the query map:</p>
+   *   <ul>
+   *   <li>requiredStringGroup - Required String in group parameters (required)</li>
+   *   <li>requiredInt64Group - Required Integer in group parameters (required)</li>
+   *   <li>stringGroup - String in group parameters (optional)</li>
+   *   <li>int64Group - Integer in group parameters (optional)</li>
+   *   </ul>
+   */
+  @RequestLine("DELETE /fake?required_string_group={requiredStringGroup}&required_int64_group={requiredInt64Group}&string_group={stringGroup}&int64_group={int64Group}")
+  @Headers({
+  "Accept: application/json",
+      "required_boolean_group: {requiredBooleanGroup}",
+      
+      "boolean_group: {booleanGroup}"
+  })
+  void testGroupParameters(@Param("requiredBooleanGroup") Boolean requiredBooleanGroup, @Param("booleanGroup") Boolean booleanGroup, @QueryMap(encoded=true) Map<String, Object> queryParams);
+
+  /**
+   * A convenience class for generating query parameters for the
+   * <code>testGroupParameters</code> method in a fluent style.
+   */
+  public static class TestGroupParametersQueryParams extends HashMap<String, Object> {
+    public TestGroupParametersQueryParams requiredStringGroup(final Integer value) {
+      put("required_string_group", EncodingUtils.encode(value));
+      return this;
+    }
+    public TestGroupParametersQueryParams requiredInt64Group(final Long value) {
+      put("required_int64_group", EncodingUtils.encode(value));
+      return this;
+    }
+    public TestGroupParametersQueryParams stringGroup(final Integer value) {
+      put("string_group", EncodingUtils.encode(value));
+      return this;
+    }
+    public TestGroupParametersQueryParams int64Group(final Long value) {
+      put("int64_group", EncodingUtils.encode(value));
+      return this;
+    }
+  }
+
+  /**
+   * test inline additionalProperties
+   * 
+   * @param param request body (required)
+   */
+  @RequestLine("POST /fake/inline-additionalProperties")
+  @Headers({
+    "Content-Type: application/json",
+    "Accept: application/json",
+  })
+  void testInlineAdditionalProperties(Map<String, String> param);
+
+  /**
+   * test json serialization of form data
+   * 
+   * @param param field1 (required)
+   * @param param2 field2 (required)
+   */
+  @RequestLine("GET /fake/jsonFormData")
+  @Headers({
+    "Content-Type: application/x-www-form-urlencoded",
+    "Accept: application/json",
+  })
+  void testJsonFormData(@Param("param") String param, @Param("param2") String param2);
+
+  /**
+   * 
+   * To test the collection format in query parameters
+   * @param pipe  (required)
+   * @param ioutil  (required)
+   * @param http  (required)
+   * @param url  (required)
+   * @param context  (required)
+   */
+  @RequestLine("PUT /fake/test-query-paramters?pipe={pipe}&ioutil={ioutil}&http={http}&url={url}&context={context}")
+  @Headers({
+    "Accept: application/json",
+  })
+  void testQueryParameterCollectionFormat(@Param("pipe") List<String> pipe, @Param("ioutil") List<String> ioutil, @Param("http") List<String> http, @Param("url") List<String> url, @Param("context") List<String> context);
+
+  /**
+   * 
+   * To test the collection format in query parameters
+   * Note, this is equivalent to the other <code>testQueryParameterCollectionFormat</code> method,
+   * but with the query parameters collected into a single Map parameter. This
+   * is convenient for services with optional query parameters, especially when
+   * used with the {@link TestQueryParameterCollectionFormatQueryParams} class that allows for
+   * building up this map in a fluent style.
+   * @param queryParams Map of query parameters as name-value pairs
+   *   <p>The following elements may be specified in the query map:</p>
+   *   <ul>
+   *   <li>pipe -  (required)</li>
+   *   <li>ioutil -  (required)</li>
+   *   <li>http -  (required)</li>
+   *   <li>url -  (required)</li>
+   *   <li>context -  (required)</li>
+   *   </ul>
+   */
+  @RequestLine("PUT /fake/test-query-paramters?pipe={pipe}&ioutil={ioutil}&http={http}&url={url}&context={context}")
+  @Headers({
+  "Accept: application/json",
+  })
+  void testQueryParameterCollectionFormat(@QueryMap(encoded=true) Map<String, Object> queryParams);
+
+  /**
+   * A convenience class for generating query parameters for the
+   * <code>testQueryParameterCollectionFormat</code> method in a fluent style.
+   */
+  public static class TestQueryParameterCollectionFormatQueryParams extends HashMap<String, Object> {
+    public TestQueryParameterCollectionFormatQueryParams pipe(final List<String> value) {
+      put("pipe", EncodingUtils.encodeCollection(value, "csv"));
+      return this;
+    }
+    public TestQueryParameterCollectionFormatQueryParams ioutil(final List<String> value) {
+      put("ioutil", EncodingUtils.encodeCollection(value, "csv"));
+      return this;
+    }
+    public TestQueryParameterCollectionFormatQueryParams http(final List<String> value) {
+      put("http", EncodingUtils.encodeCollection(value, "ssv"));
+      return this;
+    }
+    public TestQueryParameterCollectionFormatQueryParams url(final List<String> value) {
+      put("url", EncodingUtils.encodeCollection(value, "csv"));
+      return this;
+    }
+    public TestQueryParameterCollectionFormatQueryParams context(final List<String> value) {
+      put("context", EncodingUtils.encodeCollection(value, "multi"));
+      return this;
+    }
+  }
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/api/FakeClassnameTags123Api.java

@@ -0,0 +1,30 @@
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.EncodingUtils;
+
+import org.openapitools.client.model.Client;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import feign.*;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public interface FakeClassnameTags123Api extends ApiClient.Api {
+
+
+  /**
+   * To test class name in snake case
+   * To test class name in snake case
+   * @param body client model (required)
+   * @return Client
+   */
+  @RequestLine("PATCH /fake_classname_test")
+  @Headers({
+    "Content-Type: application/json",
+    "Accept: application/json",
+  })
+  Client testClassname(Client body);
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/api/PetApi.java

@@ -0,0 +1,201 @@
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.EncodingUtils;
+
+import java.io.File;
+import org.openapitools.client.model.ModelApiResponse;
+import org.openapitools.client.model.Pet;
+import java.util.Set;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import feign.*;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public interface PetApi extends ApiClient.Api {
+
+
+  /**
+   * Add a new pet to the store
+   * 
+   * @param body Pet object that needs to be added to the store (required)
+   */
+  @RequestLine("POST /pet")
+  @Headers({
+    "Content-Type: application/json",
+    "Accept: application/json",
+  })
+  void addPet(Pet body);
+
+  /**
+   * Deletes a pet
+   * 
+   * @param petId Pet id to delete (required)
+   * @param apiKey  (optional)
+   */
+  @RequestLine("DELETE /pet/{petId}")
+  @Headers({
+    "Accept: application/json",
+    "api_key: {apiKey}"
+  })
+  void deletePet(@Param("petId") Long petId, @Param("apiKey") String apiKey);
+
+  /**
+   * Finds Pets by status
+   * Multiple status values can be provided with comma separated strings
+   * @param status Status values that need to be considered for filter (required)
+   * @return List<Pet>
+   */
+  @RequestLine("GET /pet/findByStatus?status={status}")
+  @Headers({
+    "Accept: application/json",
+  })
+  List<Pet> findPetsByStatus(@Param("status") List<String> status);
+
+  /**
+   * Finds Pets by status
+   * Multiple status values can be provided with comma separated strings
+   * Note, this is equivalent to the other <code>findPetsByStatus</code> method,
+   * but with the query parameters collected into a single Map parameter. This
+   * is convenient for services with optional query parameters, especially when
+   * used with the {@link FindPetsByStatusQueryParams} class that allows for
+   * building up this map in a fluent style.
+   * @param queryParams Map of query parameters as name-value pairs
+   *   <p>The following elements may be specified in the query map:</p>
+   *   <ul>
+   *   <li>status - Status values that need to be considered for filter (required)</li>
+   *   </ul>
+   * @return List&lt;Pet&gt;
+   */
+  @RequestLine("GET /pet/findByStatus?status={status}")
+  @Headers({
+  "Accept: application/json",
+  })
+  List<Pet> findPetsByStatus(@QueryMap(encoded=true) Map<String, Object> queryParams);
+
+  /**
+   * A convenience class for generating query parameters for the
+   * <code>findPetsByStatus</code> method in a fluent style.
+   */
+  public static class FindPetsByStatusQueryParams extends HashMap<String, Object> {
+    public FindPetsByStatusQueryParams status(final List<String> value) {
+      put("status", EncodingUtils.encodeCollection(value, "csv"));
+      return this;
+    }
+  }
+
+  /**
+   * Finds Pets by tags
+   * Multiple tags can be provided with comma separated strings. Use tag1, tag2, tag3 for testing.
+   * @param tags Tags to filter by (required)
+   * @return Set&lt;Pet&gt;
+   */
+  @RequestLine("GET /pet/findByTags?tags={tags}")
+  @Headers({
+    "Accept: application/json",
+  })
+  Set<Pet> findPetsByTags(@Param("tags") Set<String> tags);
+
+  /**
+   * Finds Pets by tags
+   * Multiple tags can be provided with comma separated strings. Use tag1, tag2, tag3 for testing.
+   * Note, this is equivalent to the other <code>findPetsByTags</code> method,
+   * but with the query parameters collected into a single Map parameter. This
+   * is convenient for services with optional query parameters, especially when
+   * used with the {@link FindPetsByTagsQueryParams} class that allows for
+   * building up this map in a fluent style.
+   * @param queryParams Map of query parameters as name-value pairs
+   *   <p>The following elements may be specified in the query map:</p>
+   *   <ul>
+   *   <li>tags - Tags to filter by (required)</li>
+   *   </ul>
+   * @return Set&lt;Pet&gt;
+   */
+  @RequestLine("GET /pet/findByTags?tags={tags}")
+  @Headers({
+  "Accept: application/json",
+  })
+  Set<Pet> findPetsByTags(@QueryMap(encoded=true) Map<String, Object> queryParams);
+
+  /**
+   * A convenience class for generating query parameters for the
+   * <code>findPetsByTags</code> method in a fluent style.
+   */
+  public static class FindPetsByTagsQueryParams extends HashMap<String, Object> {
+    public FindPetsByTagsQueryParams tags(final Set<String> value) {
+      put("tags", EncodingUtils.encodeCollection(value, "csv"));
+      return this;
+    }
+  }
+
+  /**
+   * Find pet by ID
+   * Returns a single pet
+   * @param petId ID of pet to return (required)
+   * @return Pet
+   */
+  @RequestLine("GET /pet/{petId}")
+  @Headers({
+    "Accept: application/json",
+  })
+  Pet getPetById(@Param("petId") Long petId);
+
+  /**
+   * Update an existing pet
+   * 
+   * @param body Pet object that needs to be added to the store (required)
+   */
+  @RequestLine("PUT /pet")
+  @Headers({
+    "Content-Type: application/json",
+    "Accept: application/json",
+  })
+  void updatePet(Pet body);
+
+  /**
+   * Updates a pet in the store with form data
+   * 
+   * @param petId ID of pet that needs to be updated (required)
+   * @param name Updated name of the pet (optional)
+   * @param status Updated status of the pet (optional)
+   */
+  @RequestLine("POST /pet/{petId}")
+  @Headers({
+    "Content-Type: application/x-www-form-urlencoded",
+    "Accept: application/json",
+  })
+  void updatePetWithForm(@Param("petId") Long petId, @Param("name") String name, @Param("status") String status);
+
+  /**
+   * uploads an image
+   * 
+   * @param petId ID of pet to update (required)
+   * @param additionalMetadata Additional data to pass to server (optional)
+   * @param file file to upload (optional)
+   * @return ModelApiResponse
+   */
+  @RequestLine("POST /pet/{petId}/uploadImage")
+  @Headers({
+    "Content-Type: multipart/form-data",
+    "Accept: application/json",
+  })
+  ModelApiResponse uploadFile(@Param("petId") Long petId, @Param("additionalMetadata") String additionalMetadata, @Param("file") File file);
+
+  /**
+   * uploads an image (required)
+   * 
+   * @param petId ID of pet to update (required)
+   * @param requiredFile file to upload (required)
+   * @param additionalMetadata Additional data to pass to server (optional)
+   * @return ModelApiResponse
+   */
+  @RequestLine("POST /fake/{petId}/uploadImageWithRequiredFile")
+  @Headers({
+    "Content-Type: multipart/form-data",
+    "Accept: application/json",
+  })
+  ModelApiResponse uploadFileWithRequiredFile(@Param("petId") Long petId, @Param("requiredFile") File requiredFile, @Param("additionalMetadata") String additionalMetadata);
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/api/StoreApi.java

@@ -0,0 +1,64 @@
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.EncodingUtils;
+
+import org.openapitools.client.model.Order;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import feign.*;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public interface StoreApi extends ApiClient.Api {
+
+
+  /**
+   * Delete purchase order by ID
+   * For valid response try integer IDs with value < 1000. Anything above 1000 or nonintegers will generate API errors
+   * @param orderId ID of the order that needs to be deleted (required)
+   */
+  @RequestLine("DELETE /store/order/{orderId}")
+  @Headers({
+    "Accept: application/json",
+  })
+  void deleteOrder(@Param("orderId") String orderId);
+
+  /**
+   * Returns pet inventories by status
+   * Returns a map of status codes to quantities
+   * @return Map<String, Integer>
+   */
+  @RequestLine("GET /store/inventory")
+  @Headers({
+    "Accept: application/json",
+  })
+  Map<String, Integer> getInventory();
+
+  /**
+   * Find purchase order by ID
+   * For valid response try integer IDs with value &lt;&#x3D; 5 or &gt; 10. Other values will generated exceptions
+   * @param orderId ID of pet that needs to be fetched (required)
+   * @return Order
+   */
+  @RequestLine("GET /store/order/{orderId}")
+  @Headers({
+    "Accept: application/json",
+  })
+  Order getOrderById(@Param("orderId") Long orderId);
+
+  /**
+   * Place an order for a pet
+   * 
+   * @param body order placed for purchasing the pet (required)
+   * @return Order
+   */
+  @RequestLine("POST /store/order")
+  @Headers({
+    "Content-Type: */*",
+    "Accept: application/json",
+  })
+  Order placeOrder(Order body);
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/api/UserApi.java

@@ -0,0 +1,149 @@
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.EncodingUtils;
+
+import org.openapitools.client.model.User;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import feign.*;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public interface UserApi extends ApiClient.Api {
+
+
+  /**
+   * Create user
+   * This can only be done by the logged in user.
+   * @param body Created user object (required)
+   */
+  @RequestLine("POST /user")
+  @Headers({
+    "Content-Type: */*",
+    "Accept: application/json",
+  })
+  void createUser(User body);
+
+  /**
+   * Creates list of users with given input array
+   * 
+   * @param body List of user object (required)
+   */
+  @RequestLine("POST /user/createWithArray")
+  @Headers({
+    "Content-Type: */*",
+    "Accept: application/json",
+  })
+  void createUsersWithArrayInput(List<User> body);
+
+  /**
+   * Creates list of users with given input array
+   * 
+   * @param body List of user object (required)
+   */
+  @RequestLine("POST /user/createWithList")
+  @Headers({
+    "Content-Type: */*",
+    "Accept: application/json",
+  })
+  void createUsersWithListInput(List<User> body);
+
+  /**
+   * Delete user
+   * This can only be done by the logged in user.
+   * @param username The name that needs to be deleted (required)
+   */
+  @RequestLine("DELETE /user/{username}")
+  @Headers({
+    "Accept: application/json",
+  })
+  void deleteUser(@Param("username") String username);
+
+  /**
+   * Get user by user name
+   * 
+   * @param username The name that needs to be fetched. Use user1 for testing. (required)
+   * @return User
+   */
+  @RequestLine("GET /user/{username}")
+  @Headers({
+    "Accept: application/json",
+  })
+  User getUserByName(@Param("username") String username);
+
+  /**
+   * Logs user into the system
+   * 
+   * @param username The user name for login (required)
+   * @param password The password for login in clear text (required)
+   * @return String
+   */
+  @RequestLine("GET /user/login?username={username}&password={password}")
+  @Headers({
+    "Accept: application/json",
+  })
+  String loginUser(@Param("username") String username, @Param("password") String password);
+
+  /**
+   * Logs user into the system
+   * 
+   * Note, this is equivalent to the other <code>loginUser</code> method,
+   * but with the query parameters collected into a single Map parameter. This
+   * is convenient for services with optional query parameters, especially when
+   * used with the {@link LoginUserQueryParams} class that allows for
+   * building up this map in a fluent style.
+   * @param queryParams Map of query parameters as name-value pairs
+   *   <p>The following elements may be specified in the query map:</p>
+   *   <ul>
+   *   <li>username - The user name for login (required)</li>
+   *   <li>password - The password for login in clear text (required)</li>
+   *   </ul>
+   * @return String
+   */
+  @RequestLine("GET /user/login?username={username}&password={password}")
+  @Headers({
+  "Accept: application/json",
+  })
+  String loginUser(@QueryMap(encoded=true) Map<String, Object> queryParams);
+
+  /**
+   * A convenience class for generating query parameters for the
+   * <code>loginUser</code> method in a fluent style.
+   */
+  public static class LoginUserQueryParams extends HashMap<String, Object> {
+    public LoginUserQueryParams username(final String value) {
+      put("username", EncodingUtils.encode(value));
+      return this;
+    }
+    public LoginUserQueryParams password(final String value) {
+      put("password", EncodingUtils.encode(value));
+      return this;
+    }
+  }
+
+  /**
+   * Logs out current logged in user session
+   * 
+   */
+  @RequestLine("GET /user/logout")
+  @Headers({
+    "Accept: application/json",
+  })
+  void logoutUser();
+
+  /**
+   * Updated user
+   * This can only be done by the logged in user.
+   * @param username name that need to be deleted (required)
+   * @param body Updated user object (required)
+   */
+  @RequestLine("PUT /user/{username}")
+  @Headers({
+    "Content-Type: */*",
+    "Accept: application/json",
+  })
+  void updateUser(@Param("username") String username, User body);
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/auth/ApiKeyAuth.java

@@ -0,0 +1,43 @@
+package org.openapitools.client.auth;
+
+import feign.RequestInterceptor;
+import feign.RequestTemplate;
+
+public class ApiKeyAuth implements RequestInterceptor {
+    private final String location;
+    private final String paramName;
+
+    private String apiKey;
+
+    public ApiKeyAuth(String location, String paramName) {
+        this.location = location;
+        this.paramName = paramName;
+    }
+
+    public String getLocation() {
+        return location;
+    }
+
+    public String getParamName() {
+        return paramName;
+    }
+
+    public String getApiKey() {
+        return apiKey;
+    }
+
+    public void setApiKey(String apiKey) {
+        this.apiKey = apiKey;
+    }
+
+    @Override
+    public void apply(RequestTemplate template) {
+        if ("query".equals(location)) {
+            template.query(paramName, apiKey);
+        } else if ("header".equals(location)) {
+            template.header(paramName, apiKey);
+        } else if ("cookie".equals(location)) {
+            template.header("Cookie", String.format("%s=%s", paramName, apiKey));
+        }
+    }
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/auth/HttpBasicAuth.java

@@ -0,0 +1,41 @@
+package org.openapitools.client.auth;
+
+import feign.RequestInterceptor;
+import feign.RequestTemplate;
+import feign.auth.BasicAuthRequestInterceptor;
+
+/**
+ * An interceptor that adds the request header needed to use HTTP basic authentication.
+ */
+public class HttpBasicAuth implements RequestInterceptor {
+
+    private String username;
+    private String password;
+    
+    public String getUsername() {
+        return username;
+    }
+
+    public void setUsername(String username) {
+        this.username = username;
+    }
+
+    public String getPassword() {
+        return password;
+    }
+
+    public void setPassword(String password) {
+        this.password = password;
+    }
+
+    public void setCredentials(String username, String password) {
+        this.username = username;
+        this.password = password;
+    }
+
+  @Override
+  public void apply(RequestTemplate template) {
+      RequestInterceptor requestInterceptor = new BasicAuthRequestInterceptor(username, password);
+      requestInterceptor.apply(template);
+  }
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/auth/HttpBearerAuth.java

@@ -0,0 +1,43 @@
+package org.openapitools.client.auth;
+
+import feign.RequestInterceptor;
+import feign.RequestTemplate;
+
+/**
+ * An interceptor that adds the request header needed to use HTTP bearer authentication.
+ */
+public class HttpBearerAuth implements RequestInterceptor {
+  private final String scheme;
+  private String bearerToken;
+
+  public HttpBearerAuth(String scheme) {
+    this.scheme = scheme;
+  }
+
+  /**
+   * Gets the token, which together with the scheme, will be sent as the value of the Authorization header.
+   */
+  public String getBearerToken() {
+    return bearerToken;
+  }
+
+  /**
+   * Sets the token, which together with the scheme, will be sent as the value of the Authorization header.
+   */
+  public void setBearerToken(String bearerToken) {
+    this.bearerToken = bearerToken;
+  }
+
+  @Override
+  public void apply(RequestTemplate template) {
+    if(bearerToken == null) {
+      return;
+    }
+
+    template.header("Authorization", (scheme != null ? upperCaseBearer(scheme) + " " : "") + bearerToken);
+  }
+
+  private static String upperCaseBearer(String scheme) {
+    return ("bearer".equalsIgnoreCase(scheme)) ? "Bearer" : scheme;
+  }
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/auth/OAuth.java

@@ -0,0 +1,198 @@
+package org.openapitools.client.auth;
+
+import java.io.IOException;
+import java.util.Collection;
+import java.util.Map;
+import java.util.Map.Entry;
+
+import org.apache.oltu.oauth2.client.HttpClient;
+import org.apache.oltu.oauth2.client.OAuthClient;
+import org.apache.oltu.oauth2.client.request.OAuthClientRequest;
+import org.apache.oltu.oauth2.client.request.OAuthClientRequest.AuthenticationRequestBuilder;
+import org.apache.oltu.oauth2.client.request.OAuthClientRequest.TokenRequestBuilder;
+import org.apache.oltu.oauth2.client.response.OAuthClientResponse;
+import org.apache.oltu.oauth2.client.response.OAuthClientResponseFactory;
+import org.apache.oltu.oauth2.client.response.OAuthJSONAccessTokenResponse;
+import org.apache.oltu.oauth2.common.exception.OAuthProblemException;
+import org.apache.oltu.oauth2.common.exception.OAuthSystemException;
+import org.apache.oltu.oauth2.common.message.types.GrantType;
+import org.apache.oltu.oauth2.common.token.BasicOAuthToken;
+
+import feign.Client;
+import feign.Request.HttpMethod;
+import feign.Request.Options;
+import feign.RequestInterceptor;
+import feign.RequestTemplate;
+import feign.Response;
+import feign.RetryableException;
+import feign.Util;
+import org.openapitools.client.StringUtil;
+
+
+public class OAuth implements RequestInterceptor {
+
+    static final int MILLIS_PER_SECOND = 1000;
+
+    public interface AccessTokenListener {
+        void notify(BasicOAuthToken token);
+    }
+
+    private volatile String accessToken;
+    private Long expirationTimeMillis;
+    private OAuthClient oauthClient;
+    private TokenRequestBuilder tokenRequestBuilder;
+    private AuthenticationRequestBuilder authenticationRequestBuilder;
+    private AccessTokenListener accessTokenListener;
+
+    public OAuth(Client client, TokenRequestBuilder requestBuilder) {
+        this.oauthClient = new OAuthClient(new OAuthFeignClient(client));
+        this.tokenRequestBuilder = requestBuilder;
+    }
+
+    public OAuth(Client client, OAuthFlow flow, String authorizationUrl, String tokenUrl, String scopes) {
+        this(client, OAuthClientRequest.tokenLocation(tokenUrl).setScope(scopes));
+
+        switch(flow) {
+        case accessCode:
+        case implicit:
+            tokenRequestBuilder.setGrantType(GrantType.AUTHORIZATION_CODE);
+            break;
+        case password:
+            tokenRequestBuilder.setGrantType(GrantType.PASSWORD);
+            break;
+        case application:
+            tokenRequestBuilder.setGrantType(GrantType.CLIENT_CREDENTIALS);
+            break;
+        default:
+            break;
+        }
+        authenticationRequestBuilder = OAuthClientRequest.authorizationLocation(authorizationUrl);
+    }
+
+    public OAuth(OAuthFlow flow, String authorizationUrl, String tokenUrl, String scopes) {
+        this(new Client.Default(null, null), flow, authorizationUrl, tokenUrl, scopes);
+    }
+
+    @Override
+    public void apply(RequestTemplate template) {
+        // If the request already have an authorization (eg. Basic auth), do nothing
+        if (template.headers().containsKey("Authorization")) {
+            return;
+        }
+        // If first time, get the token
+        if (expirationTimeMillis == null || System.currentTimeMillis() >= expirationTimeMillis) {
+            updateAccessToken(template);
+        }
+        if (getAccessToken() != null) {
+            template.header("Authorization", "Bearer " + getAccessToken());
+        }
+    }
+
+    public synchronized void updateAccessToken(RequestTemplate template) {
+        OAuthJSONAccessTokenResponse accessTokenResponse;
+        try {
+            accessTokenResponse = oauthClient.accessToken(tokenRequestBuilder.buildBodyMessage());
+        } catch (Exception e) {
+            throw new RetryableException(0, e.getMessage(), HttpMethod.POST, e, null, template.request());
+        }
+        if (accessTokenResponse != null && accessTokenResponse.getAccessToken() != null) {
+            setAccessToken(accessTokenResponse.getAccessToken(), accessTokenResponse.getExpiresIn());
+            if (accessTokenListener != null) {
+                accessTokenListener.notify((BasicOAuthToken) accessTokenResponse.getOAuthToken());
+            }
+        }
+    }
+
+    public synchronized void registerAccessTokenListener(AccessTokenListener accessTokenListener) {
+        this.accessTokenListener = accessTokenListener;
+    }
+
+    public synchronized String getAccessToken() {
+        return accessToken;
+    }
+
+    public synchronized void setAccessToken(String accessToken, Long expiresIn) {
+        this.accessToken = accessToken;
+        this.expirationTimeMillis = expiresIn == null ? null : System.currentTimeMillis() + expiresIn * MILLIS_PER_SECOND;
+    }
+
+    public TokenRequestBuilder getTokenRequestBuilder() {
+        return tokenRequestBuilder;
+    }
+
+    public void setTokenRequestBuilder(TokenRequestBuilder tokenRequestBuilder) {
+        this.tokenRequestBuilder = tokenRequestBuilder;
+    }
+
+    public AuthenticationRequestBuilder getAuthenticationRequestBuilder() {
+        return authenticationRequestBuilder;
+    }
+
+    public void setAuthenticationRequestBuilder(AuthenticationRequestBuilder authenticationRequestBuilder) {
+        this.authenticationRequestBuilder = authenticationRequestBuilder;
+    }
+
+    public OAuthClient getOauthClient() {
+        return oauthClient;
+    }
+
+    public void setOauthClient(OAuthClient oauthClient) {
+        this.oauthClient = oauthClient;
+    }
+
+    public void setOauthClient(Client client) {
+        this.oauthClient = new OAuthClient( new OAuthFeignClient(client));
+    }
+
+    public static class OAuthFeignClient implements HttpClient {
+
+        private Client client;
+
+        public OAuthFeignClient() {
+            this.client = new Client.Default(null, null);
+        }
+
+        public OAuthFeignClient(Client client) {
+            this.client = client;
+        }
+
+        public <T extends OAuthClientResponse> T execute(OAuthClientRequest request, Map<String, String> headers,
+                String requestMethod, Class<T> responseClass)
+                        throws OAuthSystemException, OAuthProblemException {
+
+            RequestTemplate req = new RequestTemplate()
+                    .append(request.getLocationUri())
+                    .method(requestMethod)
+                    .body(request.getBody());
+
+            for (Entry<String, String> entry : headers.entrySet()) {
+                req.header(entry.getKey(), entry.getValue());
+            }
+            Response feignResponse;
+            String body = "";
+            try {
+                feignResponse = client.execute(req.request(), new Options());
+                body = Util.toString(feignResponse.body().asReader());
+            } catch (IOException e) {
+                throw new OAuthSystemException(e);
+            }
+
+            String contentType = null;
+            Collection<String> contentTypeHeader =  feignResponse.headers().get("Content-Type");
+            if(contentTypeHeader != null) {
+                contentType = StringUtil.join(contentTypeHeader.toArray(new String[0]), ";");
+            }
+
+            return OAuthClientResponseFactory.createCustomResponse(
+                    body,
+                    contentType,
+                    feignResponse.status(),
+                    responseClass
+            );
+        }
+
+        public void shutdown() {
+            // Nothing to do here
+        }
+    }
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/auth/OAuthFlow.java

@@ -0,0 +1,18 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.auth;
+
+public enum OAuthFlow {
+    accessCode, implicit, password, application
+}

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/AdditionalPropertiesAnyType.java

@@ -0,0 +1,109 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.HashMap;
+import java.util.Map;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * AdditionalPropertiesAnyType
+ */
+@JsonPropertyOrder({
+  AdditionalPropertiesAnyType.JSON_PROPERTY_NAME
+})
+@JsonTypeName("AdditionalPropertiesAnyType")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class AdditionalPropertiesAnyType extends HashMap<String, Object> {
+  public static final String JSON_PROPERTY_NAME = "name";
+  private String name;
+
+
+  public AdditionalPropertiesAnyType name(String name) {
+    
+    this.name = name;
+    return this;
+  }
+
+   /**
+   * Get name
+   * @return name
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getName() {
+    return name;
+  }
+
+
+  public void setName(String name) {
+    this.name = name;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    AdditionalPropertiesAnyType additionalPropertiesAnyType = (AdditionalPropertiesAnyType) o;
+    return Objects.equals(this.name, additionalPropertiesAnyType.name) &&
+        super.equals(o);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(name, super.hashCode());
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class AdditionalPropertiesAnyType {\n");
+    sb.append("    ").append(toIndentedString(super.toString())).append("\n");
+    sb.append("    name: ").append(toIndentedString(name)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/AdditionalPropertiesArray.java

@@ -0,0 +1,110 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * AdditionalPropertiesArray
+ */
+@JsonPropertyOrder({
+  AdditionalPropertiesArray.JSON_PROPERTY_NAME
+})
+@JsonTypeName("AdditionalPropertiesArray")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class AdditionalPropertiesArray extends HashMap<String, List> {
+  public static final String JSON_PROPERTY_NAME = "name";
+  private String name;
+
+
+  public AdditionalPropertiesArray name(String name) {
+    
+    this.name = name;
+    return this;
+  }
+
+   /**
+   * Get name
+   * @return name
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getName() {
+    return name;
+  }
+
+
+  public void setName(String name) {
+    this.name = name;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    AdditionalPropertiesArray additionalPropertiesArray = (AdditionalPropertiesArray) o;
+    return Objects.equals(this.name, additionalPropertiesArray.name) &&
+        super.equals(o);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(name, super.hashCode());
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class AdditionalPropertiesArray {\n");
+    sb.append("    ").append(toIndentedString(super.toString())).append("\n");
+    sb.append("    name: ").append(toIndentedString(name)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/AdditionalPropertiesBoolean.java

@@ -0,0 +1,109 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.HashMap;
+import java.util.Map;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * AdditionalPropertiesBoolean
+ */
+@JsonPropertyOrder({
+  AdditionalPropertiesBoolean.JSON_PROPERTY_NAME
+})
+@JsonTypeName("AdditionalPropertiesBoolean")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class AdditionalPropertiesBoolean extends HashMap<String, Boolean> {
+  public static final String JSON_PROPERTY_NAME = "name";
+  private String name;
+
+
+  public AdditionalPropertiesBoolean name(String name) {
+    
+    this.name = name;
+    return this;
+  }
+
+   /**
+   * Get name
+   * @return name
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getName() {
+    return name;
+  }
+
+
+  public void setName(String name) {
+    this.name = name;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    AdditionalPropertiesBoolean additionalPropertiesBoolean = (AdditionalPropertiesBoolean) o;
+    return Objects.equals(this.name, additionalPropertiesBoolean.name) &&
+        super.equals(o);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(name, super.hashCode());
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class AdditionalPropertiesBoolean {\n");
+    sb.append("    ").append(toIndentedString(super.toString())).append("\n");
+    sb.append("    name: ").append(toIndentedString(name)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/AdditionalPropertiesClass.java

@@ -0,0 +1,483 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.math.BigDecimal;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * AdditionalPropertiesClass
+ */
+@JsonPropertyOrder({
+  AdditionalPropertiesClass.JSON_PROPERTY_MAP_STRING,
+  AdditionalPropertiesClass.JSON_PROPERTY_MAP_NUMBER,
+  AdditionalPropertiesClass.JSON_PROPERTY_MAP_INTEGER,
+  AdditionalPropertiesClass.JSON_PROPERTY_MAP_BOOLEAN,
+  AdditionalPropertiesClass.JSON_PROPERTY_MAP_ARRAY_INTEGER,
+  AdditionalPropertiesClass.JSON_PROPERTY_MAP_ARRAY_ANYTYPE,
+  AdditionalPropertiesClass.JSON_PROPERTY_MAP_MAP_STRING,
+  AdditionalPropertiesClass.JSON_PROPERTY_MAP_MAP_ANYTYPE,
+  AdditionalPropertiesClass.JSON_PROPERTY_ANYTYPE1,
+  AdditionalPropertiesClass.JSON_PROPERTY_ANYTYPE2,
+  AdditionalPropertiesClass.JSON_PROPERTY_ANYTYPE3
+})
+@JsonTypeName("AdditionalPropertiesClass")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class AdditionalPropertiesClass {
+  public static final String JSON_PROPERTY_MAP_STRING = "map_string";
+  private Map<String, String> mapString = null;
+
+  public static final String JSON_PROPERTY_MAP_NUMBER = "map_number";
+  private Map<String, BigDecimal> mapNumber = null;
+
+  public static final String JSON_PROPERTY_MAP_INTEGER = "map_integer";
+  private Map<String, Integer> mapInteger = null;
+
+  public static final String JSON_PROPERTY_MAP_BOOLEAN = "map_boolean";
+  private Map<String, Boolean> mapBoolean = null;
+
+  public static final String JSON_PROPERTY_MAP_ARRAY_INTEGER = "map_array_integer";
+  private Map<String, List<Integer>> mapArrayInteger = null;
+
+  public static final String JSON_PROPERTY_MAP_ARRAY_ANYTYPE = "map_array_anytype";
+  private Map<String, List<Object>> mapArrayAnytype = null;
+
+  public static final String JSON_PROPERTY_MAP_MAP_STRING = "map_map_string";
+  private Map<String, Map<String, String>> mapMapString = null;
+
+  public static final String JSON_PROPERTY_MAP_MAP_ANYTYPE = "map_map_anytype";
+  private Map<String, Map<String, Object>> mapMapAnytype = null;
+
+  public static final String JSON_PROPERTY_ANYTYPE1 = "anytype_1";
+  private Object anytype1;
+
+  public static final String JSON_PROPERTY_ANYTYPE2 = "anytype_2";
+  private Object anytype2;
+
+  public static final String JSON_PROPERTY_ANYTYPE3 = "anytype_3";
+  private Object anytype3;
+
+
+  public AdditionalPropertiesClass mapString(Map<String, String> mapString) {
+    
+    this.mapString = mapString;
+    return this;
+  }
+
+  public AdditionalPropertiesClass putMapStringItem(String key, String mapStringItem) {
+    if (this.mapString == null) {
+      this.mapString = new HashMap<String, String>();
+    }
+    this.mapString.put(key, mapStringItem);
+    return this;
+  }
+
+   /**
+   * Get mapString
+   * @return mapString
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_MAP_STRING)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Map<String, String> getMapString() {
+    return mapString;
+  }
+
+
+  public void setMapString(Map<String, String> mapString) {
+    this.mapString = mapString;
+  }
+
+
+  public AdditionalPropertiesClass mapNumber(Map<String, BigDecimal> mapNumber) {
+    
+    this.mapNumber = mapNumber;
+    return this;
+  }
+
+  public AdditionalPropertiesClass putMapNumberItem(String key, BigDecimal mapNumberItem) {
+    if (this.mapNumber == null) {
+      this.mapNumber = new HashMap<String, BigDecimal>();
+    }
+    this.mapNumber.put(key, mapNumberItem);
+    return this;
+  }
+
+   /**
+   * Get mapNumber
+   * @return mapNumber
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_MAP_NUMBER)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Map<String, BigDecimal> getMapNumber() {
+    return mapNumber;
+  }
+
+
+  public void setMapNumber(Map<String, BigDecimal> mapNumber) {
+    this.mapNumber = mapNumber;
+  }
+
+
+  public AdditionalPropertiesClass mapInteger(Map<String, Integer> mapInteger) {
+    
+    this.mapInteger = mapInteger;
+    return this;
+  }
+
+  public AdditionalPropertiesClass putMapIntegerItem(String key, Integer mapIntegerItem) {
+    if (this.mapInteger == null) {
+      this.mapInteger = new HashMap<String, Integer>();
+    }
+    this.mapInteger.put(key, mapIntegerItem);
+    return this;
+  }
+
+   /**
+   * Get mapInteger
+   * @return mapInteger
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_MAP_INTEGER)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Map<String, Integer> getMapInteger() {
+    return mapInteger;
+  }
+
+
+  public void setMapInteger(Map<String, Integer> mapInteger) {
+    this.mapInteger = mapInteger;
+  }
+
+
+  public AdditionalPropertiesClass mapBoolean(Map<String, Boolean> mapBoolean) {
+    
+    this.mapBoolean = mapBoolean;
+    return this;
+  }
+
+  public AdditionalPropertiesClass putMapBooleanItem(String key, Boolean mapBooleanItem) {
+    if (this.mapBoolean == null) {
+      this.mapBoolean = new HashMap<String, Boolean>();
+    }
+    this.mapBoolean.put(key, mapBooleanItem);
+    return this;
+  }
+
+   /**
+   * Get mapBoolean
+   * @return mapBoolean
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_MAP_BOOLEAN)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Map<String, Boolean> getMapBoolean() {
+    return mapBoolean;
+  }
+
+
+  public void setMapBoolean(Map<String, Boolean> mapBoolean) {
+    this.mapBoolean = mapBoolean;
+  }
+
+
+  public AdditionalPropertiesClass mapArrayInteger(Map<String, List<Integer>> mapArrayInteger) {
+    
+    this.mapArrayInteger = mapArrayInteger;
+    return this;
+  }
+
+  public AdditionalPropertiesClass putMapArrayIntegerItem(String key, List<Integer> mapArrayIntegerItem) {
+    if (this.mapArrayInteger == null) {
+      this.mapArrayInteger = new HashMap<String, List<Integer>>();
+    }
+    this.mapArrayInteger.put(key, mapArrayIntegerItem);
+    return this;
+  }
+
+   /**
+   * Get mapArrayInteger
+   * @return mapArrayInteger
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_MAP_ARRAY_INTEGER)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Map<String, List<Integer>> getMapArrayInteger() {
+    return mapArrayInteger;
+  }
+
+
+  public void setMapArrayInteger(Map<String, List<Integer>> mapArrayInteger) {
+    this.mapArrayInteger = mapArrayInteger;
+  }
+
+
+  public AdditionalPropertiesClass mapArrayAnytype(Map<String, List<Object>> mapArrayAnytype) {
+    
+    this.mapArrayAnytype = mapArrayAnytype;
+    return this;
+  }
+
+  public AdditionalPropertiesClass putMapArrayAnytypeItem(String key, List<Object> mapArrayAnytypeItem) {
+    if (this.mapArrayAnytype == null) {
+      this.mapArrayAnytype = new HashMap<String, List<Object>>();
+    }
+    this.mapArrayAnytype.put(key, mapArrayAnytypeItem);
+    return this;
+  }
+
+   /**
+   * Get mapArrayAnytype
+   * @return mapArrayAnytype
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_MAP_ARRAY_ANYTYPE)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Map<String, List<Object>> getMapArrayAnytype() {
+    return mapArrayAnytype;
+  }
+
+
+  public void setMapArrayAnytype(Map<String, List<Object>> mapArrayAnytype) {
+    this.mapArrayAnytype = mapArrayAnytype;
+  }
+
+
+  public AdditionalPropertiesClass mapMapString(Map<String, Map<String, String>> mapMapString) {
+    
+    this.mapMapString = mapMapString;
+    return this;
+  }
+
+  public AdditionalPropertiesClass putMapMapStringItem(String key, Map<String, String> mapMapStringItem) {
+    if (this.mapMapString == null) {
+      this.mapMapString = new HashMap<String, Map<String, String>>();
+    }
+    this.mapMapString.put(key, mapMapStringItem);
+    return this;
+  }
+
+   /**
+   * Get mapMapString
+   * @return mapMapString
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_MAP_MAP_STRING)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Map<String, Map<String, String>> getMapMapString() {
+    return mapMapString;
+  }
+
+
+  public void setMapMapString(Map<String, Map<String, String>> mapMapString) {
+    this.mapMapString = mapMapString;
+  }
+
+
+  public AdditionalPropertiesClass mapMapAnytype(Map<String, Map<String, Object>> mapMapAnytype) {
+    
+    this.mapMapAnytype = mapMapAnytype;
+    return this;
+  }
+
+  public AdditionalPropertiesClass putMapMapAnytypeItem(String key, Map<String, Object> mapMapAnytypeItem) {
+    if (this.mapMapAnytype == null) {
+      this.mapMapAnytype = new HashMap<String, Map<String, Object>>();
+    }
+    this.mapMapAnytype.put(key, mapMapAnytypeItem);
+    return this;
+  }
+
+   /**
+   * Get mapMapAnytype
+   * @return mapMapAnytype
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_MAP_MAP_ANYTYPE)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Map<String, Map<String, Object>> getMapMapAnytype() {
+    return mapMapAnytype;
+  }
+
+
+  public void setMapMapAnytype(Map<String, Map<String, Object>> mapMapAnytype) {
+    this.mapMapAnytype = mapMapAnytype;
+  }
+
+
+  public AdditionalPropertiesClass anytype1(Object anytype1) {
+    
+    this.anytype1 = anytype1;
+    return this;
+  }
+
+   /**
+   * Get anytype1
+   * @return anytype1
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_ANYTYPE1)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Object getAnytype1() {
+    return anytype1;
+  }
+
+
+  public void setAnytype1(Object anytype1) {
+    this.anytype1 = anytype1;
+  }
+
+
+  public AdditionalPropertiesClass anytype2(Object anytype2) {
+    
+    this.anytype2 = anytype2;
+    return this;
+  }
+
+   /**
+   * Get anytype2
+   * @return anytype2
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_ANYTYPE2)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Object getAnytype2() {
+    return anytype2;
+  }
+
+
+  public void setAnytype2(Object anytype2) {
+    this.anytype2 = anytype2;
+  }
+
+
+  public AdditionalPropertiesClass anytype3(Object anytype3) {
+    
+    this.anytype3 = anytype3;
+    return this;
+  }
+
+   /**
+   * Get anytype3
+   * @return anytype3
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_ANYTYPE3)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Object getAnytype3() {
+    return anytype3;
+  }
+
+
+  public void setAnytype3(Object anytype3) {
+    this.anytype3 = anytype3;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    AdditionalPropertiesClass additionalPropertiesClass = (AdditionalPropertiesClass) o;
+    return Objects.equals(this.mapString, additionalPropertiesClass.mapString) &&
+        Objects.equals(this.mapNumber, additionalPropertiesClass.mapNumber) &&
+        Objects.equals(this.mapInteger, additionalPropertiesClass.mapInteger) &&
+        Objects.equals(this.mapBoolean, additionalPropertiesClass.mapBoolean) &&
+        Objects.equals(this.mapArrayInteger, additionalPropertiesClass.mapArrayInteger) &&
+        Objects.equals(this.mapArrayAnytype, additionalPropertiesClass.mapArrayAnytype) &&
+        Objects.equals(this.mapMapString, additionalPropertiesClass.mapMapString) &&
+        Objects.equals(this.mapMapAnytype, additionalPropertiesClass.mapMapAnytype) &&
+        Objects.equals(this.anytype1, additionalPropertiesClass.anytype1) &&
+        Objects.equals(this.anytype2, additionalPropertiesClass.anytype2) &&
+        Objects.equals(this.anytype3, additionalPropertiesClass.anytype3);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(mapString, mapNumber, mapInteger, mapBoolean, mapArrayInteger, mapArrayAnytype, mapMapString, mapMapAnytype, anytype1, anytype2, anytype3);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class AdditionalPropertiesClass {\n");
+    sb.append("    mapString: ").append(toIndentedString(mapString)).append("\n");
+    sb.append("    mapNumber: ").append(toIndentedString(mapNumber)).append("\n");
+    sb.append("    mapInteger: ").append(toIndentedString(mapInteger)).append("\n");
+    sb.append("    mapBoolean: ").append(toIndentedString(mapBoolean)).append("\n");
+    sb.append("    mapArrayInteger: ").append(toIndentedString(mapArrayInteger)).append("\n");
+    sb.append("    mapArrayAnytype: ").append(toIndentedString(mapArrayAnytype)).append("\n");
+    sb.append("    mapMapString: ").append(toIndentedString(mapMapString)).append("\n");
+    sb.append("    mapMapAnytype: ").append(toIndentedString(mapMapAnytype)).append("\n");
+    sb.append("    anytype1: ").append(toIndentedString(anytype1)).append("\n");
+    sb.append("    anytype2: ").append(toIndentedString(anytype2)).append("\n");
+    sb.append("    anytype3: ").append(toIndentedString(anytype3)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/AdditionalPropertiesInteger.java

@@ -0,0 +1,109 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.HashMap;
+import java.util.Map;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * AdditionalPropertiesInteger
+ */
+@JsonPropertyOrder({
+  AdditionalPropertiesInteger.JSON_PROPERTY_NAME
+})
+@JsonTypeName("AdditionalPropertiesInteger")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class AdditionalPropertiesInteger extends HashMap<String, Integer> {
+  public static final String JSON_PROPERTY_NAME = "name";
+  private String name;
+
+
+  public AdditionalPropertiesInteger name(String name) {
+    
+    this.name = name;
+    return this;
+  }
+
+   /**
+   * Get name
+   * @return name
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getName() {
+    return name;
+  }
+
+
+  public void setName(String name) {
+    this.name = name;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    AdditionalPropertiesInteger additionalPropertiesInteger = (AdditionalPropertiesInteger) o;
+    return Objects.equals(this.name, additionalPropertiesInteger.name) &&
+        super.equals(o);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(name, super.hashCode());
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class AdditionalPropertiesInteger {\n");
+    sb.append("    ").append(toIndentedString(super.toString())).append("\n");
+    sb.append("    name: ").append(toIndentedString(name)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/AdditionalPropertiesNumber.java

@@ -0,0 +1,110 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.math.BigDecimal;
+import java.util.HashMap;
+import java.util.Map;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * AdditionalPropertiesNumber
+ */
+@JsonPropertyOrder({
+  AdditionalPropertiesNumber.JSON_PROPERTY_NAME
+})
+@JsonTypeName("AdditionalPropertiesNumber")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class AdditionalPropertiesNumber extends HashMap<String, BigDecimal> {
+  public static final String JSON_PROPERTY_NAME = "name";
+  private String name;
+
+
+  public AdditionalPropertiesNumber name(String name) {
+    
+    this.name = name;
+    return this;
+  }
+
+   /**
+   * Get name
+   * @return name
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getName() {
+    return name;
+  }
+
+
+  public void setName(String name) {
+    this.name = name;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    AdditionalPropertiesNumber additionalPropertiesNumber = (AdditionalPropertiesNumber) o;
+    return Objects.equals(this.name, additionalPropertiesNumber.name) &&
+        super.equals(o);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(name, super.hashCode());
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class AdditionalPropertiesNumber {\n");
+    sb.append("    ").append(toIndentedString(super.toString())).append("\n");
+    sb.append("    name: ").append(toIndentedString(name)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/AdditionalPropertiesObject.java

@@ -0,0 +1,109 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.HashMap;
+import java.util.Map;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * AdditionalPropertiesObject
+ */
+@JsonPropertyOrder({
+  AdditionalPropertiesObject.JSON_PROPERTY_NAME
+})
+@JsonTypeName("AdditionalPropertiesObject")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class AdditionalPropertiesObject extends HashMap<String, Map> {
+  public static final String JSON_PROPERTY_NAME = "name";
+  private String name;
+
+
+  public AdditionalPropertiesObject name(String name) {
+    
+    this.name = name;
+    return this;
+  }
+
+   /**
+   * Get name
+   * @return name
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getName() {
+    return name;
+  }
+
+
+  public void setName(String name) {
+    this.name = name;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    AdditionalPropertiesObject additionalPropertiesObject = (AdditionalPropertiesObject) o;
+    return Objects.equals(this.name, additionalPropertiesObject.name) &&
+        super.equals(o);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(name, super.hashCode());
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class AdditionalPropertiesObject {\n");
+    sb.append("    ").append(toIndentedString(super.toString())).append("\n");
+    sb.append("    name: ").append(toIndentedString(name)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/AdditionalPropertiesString.java

@@ -0,0 +1,109 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.HashMap;
+import java.util.Map;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * AdditionalPropertiesString
+ */
+@JsonPropertyOrder({
+  AdditionalPropertiesString.JSON_PROPERTY_NAME
+})
+@JsonTypeName("AdditionalPropertiesString")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class AdditionalPropertiesString extends HashMap<String, String> {
+  public static final String JSON_PROPERTY_NAME = "name";
+  private String name;
+
+
+  public AdditionalPropertiesString name(String name) {
+    
+    this.name = name;
+    return this;
+  }
+
+   /**
+   * Get name
+   * @return name
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getName() {
+    return name;
+  }
+
+
+  public void setName(String name) {
+    this.name = name;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    AdditionalPropertiesString additionalPropertiesString = (AdditionalPropertiesString) o;
+    return Objects.equals(this.name, additionalPropertiesString.name) &&
+        super.equals(o);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(name, super.hashCode());
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class AdditionalPropertiesString {\n");
+    sb.append("    ").append(toIndentedString(super.toString())).append("\n");
+    sb.append("    name: ").append(toIndentedString(name)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/Animal.java

@@ -0,0 +1,147 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.openapitools.client.model.BigCat;
+import org.openapitools.client.model.Cat;
+import org.openapitools.client.model.Dog;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * Animal
+ */
+@JsonPropertyOrder({
+  Animal.JSON_PROPERTY_CLASS_NAME,
+  Animal.JSON_PROPERTY_COLOR
+})
+@JsonTypeName("Animal")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.EXISTING_PROPERTY, property = "className", visible = true)
+@JsonSubTypes({
+  @JsonSubTypes.Type(value = BigCat.class, name = "BigCat"),
+  @JsonSubTypes.Type(value = Cat.class, name = "Cat"),
+  @JsonSubTypes.Type(value = Dog.class, name = "Dog"),
+})
+
+public class Animal {
+  public static final String JSON_PROPERTY_CLASS_NAME = "className";
+  protected String className;
+
+  public static final String JSON_PROPERTY_COLOR = "color";
+  private String color = "red";
+
+
+  public Animal className(String className) {
+    
+    this.className = className;
+    return this;
+  }
+
+   /**
+   * Get className
+   * @return className
+  **/
+  @ApiModelProperty(required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_CLASS_NAME)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public String getClassName() {
+    return className;
+  }
+
+
+  public void setClassName(String className) {
+    this.className = className;
+  }
+
+
+  public Animal color(String color) {
+    
+    this.color = color;
+    return this;
+  }
+
+   /**
+   * Get color
+   * @return color
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_COLOR)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getColor() {
+    return color;
+  }
+
+
+  public void setColor(String color) {
+    this.color = color;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    Animal animal = (Animal) o;
+    return Objects.equals(this.className, animal.className) &&
+        Objects.equals(this.color, animal.color);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(className, color);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class Animal {\n");
+    sb.append("    className: ").append(toIndentedString(className)).append("\n");
+    sb.append("    color: ").append(toIndentedString(color)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/ArrayOfArrayOfNumberOnly.java

@@ -0,0 +1,116 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.math.BigDecimal;
+import java.util.ArrayList;
+import java.util.List;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * ArrayOfArrayOfNumberOnly
+ */
+@JsonPropertyOrder({
+  ArrayOfArrayOfNumberOnly.JSON_PROPERTY_ARRAY_ARRAY_NUMBER
+})
+@JsonTypeName("ArrayOfArrayOfNumberOnly")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class ArrayOfArrayOfNumberOnly {
+  public static final String JSON_PROPERTY_ARRAY_ARRAY_NUMBER = "ArrayArrayNumber";
+  private List<List<BigDecimal>> arrayArrayNumber = null;
+
+
+  public ArrayOfArrayOfNumberOnly arrayArrayNumber(List<List<BigDecimal>> arrayArrayNumber) {
+    
+    this.arrayArrayNumber = arrayArrayNumber;
+    return this;
+  }
+
+  public ArrayOfArrayOfNumberOnly addArrayArrayNumberItem(List<BigDecimal> arrayArrayNumberItem) {
+    if (this.arrayArrayNumber == null) {
+      this.arrayArrayNumber = new ArrayList<List<BigDecimal>>();
+    }
+    this.arrayArrayNumber.add(arrayArrayNumberItem);
+    return this;
+  }
+
+   /**
+   * Get arrayArrayNumber
+   * @return arrayArrayNumber
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_ARRAY_ARRAY_NUMBER)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public List<List<BigDecimal>> getArrayArrayNumber() {
+    return arrayArrayNumber;
+  }
+
+
+  public void setArrayArrayNumber(List<List<BigDecimal>> arrayArrayNumber) {
+    this.arrayArrayNumber = arrayArrayNumber;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    ArrayOfArrayOfNumberOnly arrayOfArrayOfNumberOnly = (ArrayOfArrayOfNumberOnly) o;
+    return Objects.equals(this.arrayArrayNumber, arrayOfArrayOfNumberOnly.arrayArrayNumber);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(arrayArrayNumber);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class ArrayOfArrayOfNumberOnly {\n");
+    sb.append("    arrayArrayNumber: ").append(toIndentedString(arrayArrayNumber)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/ArrayOfNumberOnly.java

@@ -0,0 +1,116 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.math.BigDecimal;
+import java.util.ArrayList;
+import java.util.List;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * ArrayOfNumberOnly
+ */
+@JsonPropertyOrder({
+  ArrayOfNumberOnly.JSON_PROPERTY_ARRAY_NUMBER
+})
+@JsonTypeName("ArrayOfNumberOnly")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class ArrayOfNumberOnly {
+  public static final String JSON_PROPERTY_ARRAY_NUMBER = "ArrayNumber";
+  private List<BigDecimal> arrayNumber = null;
+
+
+  public ArrayOfNumberOnly arrayNumber(List<BigDecimal> arrayNumber) {
+    
+    this.arrayNumber = arrayNumber;
+    return this;
+  }
+
+  public ArrayOfNumberOnly addArrayNumberItem(BigDecimal arrayNumberItem) {
+    if (this.arrayNumber == null) {
+      this.arrayNumber = new ArrayList<BigDecimal>();
+    }
+    this.arrayNumber.add(arrayNumberItem);
+    return this;
+  }
+
+   /**
+   * Get arrayNumber
+   * @return arrayNumber
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_ARRAY_NUMBER)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public List<BigDecimal> getArrayNumber() {
+    return arrayNumber;
+  }
+
+
+  public void setArrayNumber(List<BigDecimal> arrayNumber) {
+    this.arrayNumber = arrayNumber;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    ArrayOfNumberOnly arrayOfNumberOnly = (ArrayOfNumberOnly) o;
+    return Objects.equals(this.arrayNumber, arrayOfNumberOnly.arrayNumber);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(arrayNumber);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class ArrayOfNumberOnly {\n");
+    sb.append("    arrayNumber: ").append(toIndentedString(arrayNumber)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/ArrayTest.java

@@ -0,0 +1,194 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.ArrayList;
+import java.util.List;
+import org.openapitools.client.model.ReadOnlyFirst;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * ArrayTest
+ */
+@JsonPropertyOrder({
+  ArrayTest.JSON_PROPERTY_ARRAY_OF_STRING,
+  ArrayTest.JSON_PROPERTY_ARRAY_ARRAY_OF_INTEGER,
+  ArrayTest.JSON_PROPERTY_ARRAY_ARRAY_OF_MODEL
+})
+@JsonTypeName("ArrayTest")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class ArrayTest {
+  public static final String JSON_PROPERTY_ARRAY_OF_STRING = "array_of_string";
+  private List<String> arrayOfString = null;
+
+  public static final String JSON_PROPERTY_ARRAY_ARRAY_OF_INTEGER = "array_array_of_integer";
+  private List<List<Long>> arrayArrayOfInteger = null;
+
+  public static final String JSON_PROPERTY_ARRAY_ARRAY_OF_MODEL = "array_array_of_model";
+  private List<List<ReadOnlyFirst>> arrayArrayOfModel = null;
+
+
+  public ArrayTest arrayOfString(List<String> arrayOfString) {
+    
+    this.arrayOfString = arrayOfString;
+    return this;
+  }
+
+  public ArrayTest addArrayOfStringItem(String arrayOfStringItem) {
+    if (this.arrayOfString == null) {
+      this.arrayOfString = new ArrayList<String>();
+    }
+    this.arrayOfString.add(arrayOfStringItem);
+    return this;
+  }
+
+   /**
+   * Get arrayOfString
+   * @return arrayOfString
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_ARRAY_OF_STRING)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public List<String> getArrayOfString() {
+    return arrayOfString;
+  }
+
+
+  public void setArrayOfString(List<String> arrayOfString) {
+    this.arrayOfString = arrayOfString;
+  }
+
+
+  public ArrayTest arrayArrayOfInteger(List<List<Long>> arrayArrayOfInteger) {
+    
+    this.arrayArrayOfInteger = arrayArrayOfInteger;
+    return this;
+  }
+
+  public ArrayTest addArrayArrayOfIntegerItem(List<Long> arrayArrayOfIntegerItem) {
+    if (this.arrayArrayOfInteger == null) {
+      this.arrayArrayOfInteger = new ArrayList<List<Long>>();
+    }
+    this.arrayArrayOfInteger.add(arrayArrayOfIntegerItem);
+    return this;
+  }
+
+   /**
+   * Get arrayArrayOfInteger
+   * @return arrayArrayOfInteger
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_ARRAY_ARRAY_OF_INTEGER)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public List<List<Long>> getArrayArrayOfInteger() {
+    return arrayArrayOfInteger;
+  }
+
+
+  public void setArrayArrayOfInteger(List<List<Long>> arrayArrayOfInteger) {
+    this.arrayArrayOfInteger = arrayArrayOfInteger;
+  }
+
+
+  public ArrayTest arrayArrayOfModel(List<List<ReadOnlyFirst>> arrayArrayOfModel) {
+    
+    this.arrayArrayOfModel = arrayArrayOfModel;
+    return this;
+  }
+
+  public ArrayTest addArrayArrayOfModelItem(List<ReadOnlyFirst> arrayArrayOfModelItem) {
+    if (this.arrayArrayOfModel == null) {
+      this.arrayArrayOfModel = new ArrayList<List<ReadOnlyFirst>>();
+    }
+    this.arrayArrayOfModel.add(arrayArrayOfModelItem);
+    return this;
+  }
+
+   /**
+   * Get arrayArrayOfModel
+   * @return arrayArrayOfModel
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_ARRAY_ARRAY_OF_MODEL)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public List<List<ReadOnlyFirst>> getArrayArrayOfModel() {
+    return arrayArrayOfModel;
+  }
+
+
+  public void setArrayArrayOfModel(List<List<ReadOnlyFirst>> arrayArrayOfModel) {
+    this.arrayArrayOfModel = arrayArrayOfModel;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    ArrayTest arrayTest = (ArrayTest) o;
+    return Objects.equals(this.arrayOfString, arrayTest.arrayOfString) &&
+        Objects.equals(this.arrayArrayOfInteger, arrayTest.arrayArrayOfInteger) &&
+        Objects.equals(this.arrayArrayOfModel, arrayTest.arrayArrayOfModel);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(arrayOfString, arrayArrayOfInteger, arrayArrayOfModel);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class ArrayTest {\n");
+    sb.append("    arrayOfString: ").append(toIndentedString(arrayOfString)).append("\n");
+    sb.append("    arrayArrayOfInteger: ").append(toIndentedString(arrayArrayOfInteger)).append("\n");
+    sb.append("    arrayArrayOfModel: ").append(toIndentedString(arrayArrayOfModel)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/BigCat.java

@@ -0,0 +1,152 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.openapitools.client.model.BigCatAllOf;
+import org.openapitools.client.model.Cat;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * BigCat
+ */
+@JsonPropertyOrder({
+  BigCat.JSON_PROPERTY_KIND
+})
+@JsonTypeName("BigCat")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.EXISTING_PROPERTY, property = "className", visible = true)
+
+public class BigCat extends Cat {
+  /**
+   * Gets or Sets kind
+   */
+  public enum KindEnum {
+    LIONS("lions"),
+    
+    TIGERS("tigers"),
+    
+    LEOPARDS("leopards"),
+    
+    JAGUARS("jaguars");
+
+    private String value;
+
+    KindEnum(String value) {
+      this.value = value;
+    }
+
+    @JsonValue
+    public String getValue() {
+      return value;
+    }
+
+    @Override
+    public String toString() {
+      return String.valueOf(value);
+    }
+
+    @JsonCreator
+    public static KindEnum fromValue(String value) {
+      for (KindEnum b : KindEnum.values()) {
+        if (b.value.equals(value)) {
+          return b;
+        }
+      }
+      throw new IllegalArgumentException("Unexpected value '" + value + "'");
+    }
+  }
+
+  public static final String JSON_PROPERTY_KIND = "kind";
+  private KindEnum kind;
+
+
+  public BigCat kind(KindEnum kind) {
+    
+    this.kind = kind;
+    return this;
+  }
+
+   /**
+   * Get kind
+   * @return kind
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_KIND)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public KindEnum getKind() {
+    return kind;
+  }
+
+
+  public void setKind(KindEnum kind) {
+    this.kind = kind;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    BigCat bigCat = (BigCat) o;
+    return Objects.equals(this.kind, bigCat.kind) &&
+        super.equals(o);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(kind, super.hashCode());
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class BigCat {\n");
+    sb.append("    ").append(toIndentedString(super.toString())).append("\n");
+    sb.append("    kind: ").append(toIndentedString(kind)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/BigCatAllOf.java

@@ -0,0 +1,144 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * BigCatAllOf
+ */
+@JsonPropertyOrder({
+  BigCatAllOf.JSON_PROPERTY_KIND
+})
+@JsonTypeName("BigCat_allOf")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class BigCatAllOf {
+  /**
+   * Gets or Sets kind
+   */
+  public enum KindEnum {
+    LIONS("lions"),
+    
+    TIGERS("tigers"),
+    
+    LEOPARDS("leopards"),
+    
+    JAGUARS("jaguars");
+
+    private String value;
+
+    KindEnum(String value) {
+      this.value = value;
+    }
+
+    @JsonValue
+    public String getValue() {
+      return value;
+    }
+
+    @Override
+    public String toString() {
+      return String.valueOf(value);
+    }
+
+    @JsonCreator
+    public static KindEnum fromValue(String value) {
+      for (KindEnum b : KindEnum.values()) {
+        if (b.value.equals(value)) {
+          return b;
+        }
+      }
+      throw new IllegalArgumentException("Unexpected value '" + value + "'");
+    }
+  }
+
+  public static final String JSON_PROPERTY_KIND = "kind";
+  private KindEnum kind;
+
+
+  public BigCatAllOf kind(KindEnum kind) {
+    
+    this.kind = kind;
+    return this;
+  }
+
+   /**
+   * Get kind
+   * @return kind
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_KIND)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public KindEnum getKind() {
+    return kind;
+  }
+
+
+  public void setKind(KindEnum kind) {
+    this.kind = kind;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    BigCatAllOf bigCatAllOf = (BigCatAllOf) o;
+    return Objects.equals(this.kind, bigCatAllOf.kind);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(kind);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class BigCatAllOf {\n");
+    sb.append("    kind: ").append(toIndentedString(kind)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/Capitalization.java

@@ -0,0 +1,260 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * Capitalization
+ */
+@JsonPropertyOrder({
+  Capitalization.JSON_PROPERTY_SMALL_CAMEL,
+  Capitalization.JSON_PROPERTY_CAPITAL_CAMEL,
+  Capitalization.JSON_PROPERTY_SMALL_SNAKE,
+  Capitalization.JSON_PROPERTY_CAPITAL_SNAKE,
+  Capitalization.JSON_PROPERTY_SC_A_E_T_H_FLOW_POINTS,
+  Capitalization.JSON_PROPERTY_A_T_T_N_A_M_E
+})
+@JsonTypeName("Capitalization")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Capitalization {
+  public static final String JSON_PROPERTY_SMALL_CAMEL = "smallCamel";
+  private String smallCamel;
+
+  public static final String JSON_PROPERTY_CAPITAL_CAMEL = "CapitalCamel";
+  private String capitalCamel;
+
+  public static final String JSON_PROPERTY_SMALL_SNAKE = "small_Snake";
+  private String smallSnake;
+
+  public static final String JSON_PROPERTY_CAPITAL_SNAKE = "Capital_Snake";
+  private String capitalSnake;
+
+  public static final String JSON_PROPERTY_SC_A_E_T_H_FLOW_POINTS = "SCA_ETH_Flow_Points";
+  private String scAETHFlowPoints;
+
+  public static final String JSON_PROPERTY_A_T_T_N_A_M_E = "ATT_NAME";
+  private String ATT_NAME;
+
+
+  public Capitalization smallCamel(String smallCamel) {
+    
+    this.smallCamel = smallCamel;
+    return this;
+  }
+
+   /**
+   * Get smallCamel
+   * @return smallCamel
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_SMALL_CAMEL)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getSmallCamel() {
+    return smallCamel;
+  }
+
+
+  public void setSmallCamel(String smallCamel) {
+    this.smallCamel = smallCamel;
+  }
+
+
+  public Capitalization capitalCamel(String capitalCamel) {
+    
+    this.capitalCamel = capitalCamel;
+    return this;
+  }
+
+   /**
+   * Get capitalCamel
+   * @return capitalCamel
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_CAPITAL_CAMEL)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getCapitalCamel() {
+    return capitalCamel;
+  }
+
+
+  public void setCapitalCamel(String capitalCamel) {
+    this.capitalCamel = capitalCamel;
+  }
+
+
+  public Capitalization smallSnake(String smallSnake) {
+    
+    this.smallSnake = smallSnake;
+    return this;
+  }
+
+   /**
+   * Get smallSnake
+   * @return smallSnake
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_SMALL_SNAKE)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getSmallSnake() {
+    return smallSnake;
+  }
+
+
+  public void setSmallSnake(String smallSnake) {
+    this.smallSnake = smallSnake;
+  }
+
+
+  public Capitalization capitalSnake(String capitalSnake) {
+    
+    this.capitalSnake = capitalSnake;
+    return this;
+  }
+
+   /**
+   * Get capitalSnake
+   * @return capitalSnake
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_CAPITAL_SNAKE)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getCapitalSnake() {
+    return capitalSnake;
+  }
+
+
+  public void setCapitalSnake(String capitalSnake) {
+    this.capitalSnake = capitalSnake;
+  }
+
+
+  public Capitalization scAETHFlowPoints(String scAETHFlowPoints) {
+    
+    this.scAETHFlowPoints = scAETHFlowPoints;
+    return this;
+  }
+
+   /**
+   * Get scAETHFlowPoints
+   * @return scAETHFlowPoints
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_SC_A_E_T_H_FLOW_POINTS)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getScAETHFlowPoints() {
+    return scAETHFlowPoints;
+  }
+
+
+  public void setScAETHFlowPoints(String scAETHFlowPoints) {
+    this.scAETHFlowPoints = scAETHFlowPoints;
+  }
+
+
+  public Capitalization ATT_NAME(String ATT_NAME) {
+    
+    this.ATT_NAME = ATT_NAME;
+    return this;
+  }
+
+   /**
+   * Name of the pet 
+   * @return ATT_NAME
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "Name of the pet ")
+  @JsonProperty(JSON_PROPERTY_A_T_T_N_A_M_E)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getATTNAME() {
+    return ATT_NAME;
+  }
+
+
+  public void setATTNAME(String ATT_NAME) {
+    this.ATT_NAME = ATT_NAME;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    Capitalization capitalization = (Capitalization) o;
+    return Objects.equals(this.smallCamel, capitalization.smallCamel) &&
+        Objects.equals(this.capitalCamel, capitalization.capitalCamel) &&
+        Objects.equals(this.smallSnake, capitalization.smallSnake) &&
+        Objects.equals(this.capitalSnake, capitalization.capitalSnake) &&
+        Objects.equals(this.scAETHFlowPoints, capitalization.scAETHFlowPoints) &&
+        Objects.equals(this.ATT_NAME, capitalization.ATT_NAME);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(smallCamel, capitalCamel, smallSnake, capitalSnake, scAETHFlowPoints, ATT_NAME);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class Capitalization {\n");
+    sb.append("    smallCamel: ").append(toIndentedString(smallCamel)).append("\n");
+    sb.append("    capitalCamel: ").append(toIndentedString(capitalCamel)).append("\n");
+    sb.append("    smallSnake: ").append(toIndentedString(smallSnake)).append("\n");
+    sb.append("    capitalSnake: ").append(toIndentedString(capitalSnake)).append("\n");
+    sb.append("    scAETHFlowPoints: ").append(toIndentedString(scAETHFlowPoints)).append("\n");
+    sb.append("    ATT_NAME: ").append(toIndentedString(ATT_NAME)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/Cat.java

@@ -0,0 +1,117 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.openapitools.client.model.Animal;
+import org.openapitools.client.model.BigCat;
+import org.openapitools.client.model.CatAllOf;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * Cat
+ */
+@JsonPropertyOrder({
+  Cat.JSON_PROPERTY_DECLAWED
+})
+@JsonTypeName("Cat")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.EXISTING_PROPERTY, property = "className", visible = true)
+@JsonSubTypes({
+  @JsonSubTypes.Type(value = BigCat.class, name = "BigCat"),
+})
+
+public class Cat extends Animal {
+  public static final String JSON_PROPERTY_DECLAWED = "declawed";
+  private Boolean declawed;
+
+
+  public Cat declawed(Boolean declawed) {
+    
+    this.declawed = declawed;
+    return this;
+  }
+
+   /**
+   * Get declawed
+   * @return declawed
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_DECLAWED)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Boolean isDeclawed() {
+    return declawed;
+  }
+
+
+  public void setDeclawed(Boolean declawed) {
+    this.declawed = declawed;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    Cat cat = (Cat) o;
+    return Objects.equals(this.declawed, cat.declawed) &&
+        super.equals(o);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(declawed, super.hashCode());
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class Cat {\n");
+    sb.append("    ").append(toIndentedString(super.toString())).append("\n");
+    sb.append("    declawed: ").append(toIndentedString(declawed)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/CatAllOf.java

@@ -0,0 +1,105 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * CatAllOf
+ */
+@JsonPropertyOrder({
+  CatAllOf.JSON_PROPERTY_DECLAWED
+})
+@JsonTypeName("Cat_allOf")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class CatAllOf {
+  public static final String JSON_PROPERTY_DECLAWED = "declawed";
+  private Boolean declawed;
+
+
+  public CatAllOf declawed(Boolean declawed) {
+    
+    this.declawed = declawed;
+    return this;
+  }
+
+   /**
+   * Get declawed
+   * @return declawed
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_DECLAWED)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Boolean isDeclawed() {
+    return declawed;
+  }
+
+
+  public void setDeclawed(Boolean declawed) {
+    this.declawed = declawed;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    CatAllOf catAllOf = (CatAllOf) o;
+    return Objects.equals(this.declawed, catAllOf.declawed);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(declawed);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class CatAllOf {\n");
+    sb.append("    declawed: ").append(toIndentedString(declawed)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/Category.java

@@ -0,0 +1,135 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * Category
+ */
+@JsonPropertyOrder({
+  Category.JSON_PROPERTY_ID,
+  Category.JSON_PROPERTY_NAME
+})
+@JsonTypeName("Category")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Category {
+  public static final String JSON_PROPERTY_ID = "id";
+  private Long id;
+
+  public static final String JSON_PROPERTY_NAME = "name";
+  private String name = "default-name";
+
+
+  public Category id(Long id) {
+    
+    this.id = id;
+    return this;
+  }
+
+   /**
+   * Get id
+   * @return id
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_ID)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Long getId() {
+    return id;
+  }
+
+
+  public void setId(Long id) {
+    this.id = id;
+  }
+
+
+  public Category name(String name) {
+    
+    this.name = name;
+    return this;
+  }
+
+   /**
+   * Get name
+   * @return name
+  **/
+  @ApiModelProperty(required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public String getName() {
+    return name;
+  }
+
+
+  public void setName(String name) {
+    this.name = name;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    Category category = (Category) o;
+    return Objects.equals(this.id, category.id) &&
+        Objects.equals(this.name, category.name);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(id, name);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class Category {\n");
+    sb.append("    id: ").append(toIndentedString(id)).append("\n");
+    sb.append("    name: ").append(toIndentedString(name)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/ClassModel.java

@@ -0,0 +1,106 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * Model for testing model with \"_class\" property
+ */
+@ApiModel(description = "Model for testing model with \"_class\" property")
+@JsonPropertyOrder({
+  ClassModel.JSON_PROPERTY_PROPERTY_CLASS
+})
+@JsonTypeName("ClassModel")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class ClassModel {
+  public static final String JSON_PROPERTY_PROPERTY_CLASS = "_class";
+  private String propertyClass;
+
+
+  public ClassModel propertyClass(String propertyClass) {
+    
+    this.propertyClass = propertyClass;
+    return this;
+  }
+
+   /**
+   * Get propertyClass
+   * @return propertyClass
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_PROPERTY_CLASS)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getPropertyClass() {
+    return propertyClass;
+  }
+
+
+  public void setPropertyClass(String propertyClass) {
+    this.propertyClass = propertyClass;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    ClassModel classModel = (ClassModel) o;
+    return Objects.equals(this.propertyClass, classModel.propertyClass);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(propertyClass);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class ClassModel {\n");
+    sb.append("    propertyClass: ").append(toIndentedString(propertyClass)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/Client.java

@@ -0,0 +1,105 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * Client
+ */
+@JsonPropertyOrder({
+  Client.JSON_PROPERTY_CLIENT
+})
+@JsonTypeName("Client")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Client {
+  public static final String JSON_PROPERTY_CLIENT = "client";
+  private String client;
+
+
+  public Client client(String client) {
+    
+    this.client = client;
+    return this;
+  }
+
+   /**
+   * Get client
+   * @return client
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_CLIENT)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getClient() {
+    return client;
+  }
+
+
+  public void setClient(String client) {
+    this.client = client;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    Client client = (Client) o;
+    return Objects.equals(this.client, client.client);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(client);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class Client {\n");
+    sb.append("    client: ").append(toIndentedString(client)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/Dog.java

@@ -0,0 +1,113 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.openapitools.client.model.Animal;
+import org.openapitools.client.model.DogAllOf;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * Dog
+ */
+@JsonPropertyOrder({
+  Dog.JSON_PROPERTY_BREED
+})
+@JsonTypeName("Dog")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.EXISTING_PROPERTY, property = "className", visible = true)
+
+public class Dog extends Animal {
+  public static final String JSON_PROPERTY_BREED = "breed";
+  private String breed;
+
+
+  public Dog breed(String breed) {
+    
+    this.breed = breed;
+    return this;
+  }
+
+   /**
+   * Get breed
+   * @return breed
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_BREED)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getBreed() {
+    return breed;
+  }
+
+
+  public void setBreed(String breed) {
+    this.breed = breed;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    Dog dog = (Dog) o;
+    return Objects.equals(this.breed, dog.breed) &&
+        super.equals(o);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(breed, super.hashCode());
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class Dog {\n");
+    sb.append("    ").append(toIndentedString(super.toString())).append("\n");
+    sb.append("    breed: ").append(toIndentedString(breed)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/DogAllOf.java

@@ -0,0 +1,105 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * DogAllOf
+ */
+@JsonPropertyOrder({
+  DogAllOf.JSON_PROPERTY_BREED
+})
+@JsonTypeName("Dog_allOf")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class DogAllOf {
+  public static final String JSON_PROPERTY_BREED = "breed";
+  private String breed;
+
+
+  public DogAllOf breed(String breed) {
+    
+    this.breed = breed;
+    return this;
+  }
+
+   /**
+   * Get breed
+   * @return breed
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_BREED)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getBreed() {
+    return breed;
+  }
+
+
+  public void setBreed(String breed) {
+    this.breed = breed;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    DogAllOf dogAllOf = (DogAllOf) o;
+    return Objects.equals(this.breed, dogAllOf.breed);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(breed);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class DogAllOf {\n");
+    sb.append("    breed: ").append(toIndentedString(breed)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/EnumArrays.java

@@ -0,0 +1,216 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.ArrayList;
+import java.util.List;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * EnumArrays
+ */
+@JsonPropertyOrder({
+  EnumArrays.JSON_PROPERTY_JUST_SYMBOL,
+  EnumArrays.JSON_PROPERTY_ARRAY_ENUM
+})
+@JsonTypeName("EnumArrays")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class EnumArrays {
+  /**
+   * Gets or Sets justSymbol
+   */
+  public enum JustSymbolEnum {
+    GREATER_THAN_OR_EQUAL_TO(">="),
+    
+    DOLLAR("$");
+
+    private String value;
+
+    JustSymbolEnum(String value) {
+      this.value = value;
+    }
+
+    @JsonValue
+    public String getValue() {
+      return value;
+    }
+
+    @Override
+    public String toString() {
+      return String.valueOf(value);
+    }
+
+    @JsonCreator
+    public static JustSymbolEnum fromValue(String value) {
+      for (JustSymbolEnum b : JustSymbolEnum.values()) {
+        if (b.value.equals(value)) {
+          return b;
+        }
+      }
+      throw new IllegalArgumentException("Unexpected value '" + value + "'");
+    }
+  }
+
+  public static final String JSON_PROPERTY_JUST_SYMBOL = "just_symbol";
+  private JustSymbolEnum justSymbol;
+
+  /**
+   * Gets or Sets arrayEnum
+   */
+  public enum ArrayEnumEnum {
+    FISH("fish"),
+    
+    CRAB("crab");
+
+    private String value;
+
+    ArrayEnumEnum(String value) {
+      this.value = value;
+    }
+
+    @JsonValue
+    public String getValue() {
+      return value;
+    }
+
+    @Override
+    public String toString() {
+      return String.valueOf(value);
+    }
+
+    @JsonCreator
+    public static ArrayEnumEnum fromValue(String value) {
+      for (ArrayEnumEnum b : ArrayEnumEnum.values()) {
+        if (b.value.equals(value)) {
+          return b;
+        }
+      }
+      throw new IllegalArgumentException("Unexpected value '" + value + "'");
+    }
+  }
+
+  public static final String JSON_PROPERTY_ARRAY_ENUM = "array_enum";
+  private List<ArrayEnumEnum> arrayEnum = null;
+
+
+  public EnumArrays justSymbol(JustSymbolEnum justSymbol) {
+    
+    this.justSymbol = justSymbol;
+    return this;
+  }
+
+   /**
+   * Get justSymbol
+   * @return justSymbol
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_JUST_SYMBOL)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public JustSymbolEnum getJustSymbol() {
+    return justSymbol;
+  }
+
+
+  public void setJustSymbol(JustSymbolEnum justSymbol) {
+    this.justSymbol = justSymbol;
+  }
+
+
+  public EnumArrays arrayEnum(List<ArrayEnumEnum> arrayEnum) {
+    
+    this.arrayEnum = arrayEnum;
+    return this;
+  }
+
+  public EnumArrays addArrayEnumItem(ArrayEnumEnum arrayEnumItem) {
+    if (this.arrayEnum == null) {
+      this.arrayEnum = new ArrayList<ArrayEnumEnum>();
+    }
+    this.arrayEnum.add(arrayEnumItem);
+    return this;
+  }
+
+   /**
+   * Get arrayEnum
+   * @return arrayEnum
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_ARRAY_ENUM)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public List<ArrayEnumEnum> getArrayEnum() {
+    return arrayEnum;
+  }
+
+
+  public void setArrayEnum(List<ArrayEnumEnum> arrayEnum) {
+    this.arrayEnum = arrayEnum;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    EnumArrays enumArrays = (EnumArrays) o;
+    return Objects.equals(this.justSymbol, enumArrays.justSymbol) &&
+        Objects.equals(this.arrayEnum, enumArrays.arrayEnum);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(justSymbol, arrayEnum);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class EnumArrays {\n");
+    sb.append("    justSymbol: ").append(toIndentedString(justSymbol)).append("\n");
+    sb.append("    arrayEnum: ").append(toIndentedString(arrayEnum)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/EnumClass.java

@@ -0,0 +1,60 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonValue;
+
+/**
+ * Gets or Sets EnumClass
+ */
+public enum EnumClass {
+  
+  _ABC("_abc"),
+  
+  _EFG("-efg"),
+  
+  _XYZ_("(xyz)");
+
+  private String value;
+
+  EnumClass(String value) {
+    this.value = value;
+  }
+
+  @JsonValue
+  public String getValue() {
+    return value;
+  }
+
+  @Override
+  public String toString() {
+    return String.valueOf(value);
+  }
+
+  @JsonCreator
+  public static EnumClass fromValue(String value) {
+    for (EnumClass b : EnumClass.values()) {
+      if (b.value.equals(value)) {
+        return b;
+      }
+    }
+    throw new IllegalArgumentException("Unexpected value '" + value + "'");
+  }
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/EnumTest.java

@@ -0,0 +1,373 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.openapitools.client.model.OuterEnum;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * EnumTest
+ */
+@JsonPropertyOrder({
+  EnumTest.JSON_PROPERTY_ENUM_STRING,
+  EnumTest.JSON_PROPERTY_ENUM_STRING_REQUIRED,
+  EnumTest.JSON_PROPERTY_ENUM_INTEGER,
+  EnumTest.JSON_PROPERTY_ENUM_NUMBER,
+  EnumTest.JSON_PROPERTY_OUTER_ENUM
+})
+@JsonTypeName("Enum_Test")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class EnumTest {
+  /**
+   * Gets or Sets enumString
+   */
+  public enum EnumStringEnum {
+    UPPER("UPPER"),
+    
+    LOWER("lower"),
+    
+    EMPTY("");
+
+    private String value;
+
+    EnumStringEnum(String value) {
+      this.value = value;
+    }
+
+    @JsonValue
+    public String getValue() {
+      return value;
+    }
+
+    @Override
+    public String toString() {
+      return String.valueOf(value);
+    }
+
+    @JsonCreator
+    public static EnumStringEnum fromValue(String value) {
+      for (EnumStringEnum b : EnumStringEnum.values()) {
+        if (b.value.equals(value)) {
+          return b;
+        }
+      }
+      throw new IllegalArgumentException("Unexpected value '" + value + "'");
+    }
+  }
+
+  public static final String JSON_PROPERTY_ENUM_STRING = "enum_string";
+  private EnumStringEnum enumString;
+
+  /**
+   * Gets or Sets enumStringRequired
+   */
+  public enum EnumStringRequiredEnum {
+    UPPER("UPPER"),
+    
+    LOWER("lower"),
+    
+    EMPTY("");
+
+    private String value;
+
+    EnumStringRequiredEnum(String value) {
+      this.value = value;
+    }
+
+    @JsonValue
+    public String getValue() {
+      return value;
+    }
+
+    @Override
+    public String toString() {
+      return String.valueOf(value);
+    }
+
+    @JsonCreator
+    public static EnumStringRequiredEnum fromValue(String value) {
+      for (EnumStringRequiredEnum b : EnumStringRequiredEnum.values()) {
+        if (b.value.equals(value)) {
+          return b;
+        }
+      }
+      throw new IllegalArgumentException("Unexpected value '" + value + "'");
+    }
+  }
+
+  public static final String JSON_PROPERTY_ENUM_STRING_REQUIRED = "enum_string_required";
+  private EnumStringRequiredEnum enumStringRequired;
+
+  /**
+   * Gets or Sets enumInteger
+   */
+  public enum EnumIntegerEnum {
+    NUMBER_1(1),
+    
+    NUMBER_MINUS_1(-1);
+
+    private Integer value;
+
+    EnumIntegerEnum(Integer value) {
+      this.value = value;
+    }
+
+    @JsonValue
+    public Integer getValue() {
+      return value;
+    }
+
+    @Override
+    public String toString() {
+      return String.valueOf(value);
+    }
+
+    @JsonCreator
+    public static EnumIntegerEnum fromValue(Integer value) {
+      for (EnumIntegerEnum b : EnumIntegerEnum.values()) {
+        if (b.value.equals(value)) {
+          return b;
+        }
+      }
+      throw new IllegalArgumentException("Unexpected value '" + value + "'");
+    }
+  }
+
+  public static final String JSON_PROPERTY_ENUM_INTEGER = "enum_integer";
+  private EnumIntegerEnum enumInteger;
+
+  /**
+   * Gets or Sets enumNumber
+   */
+  public enum EnumNumberEnum {
+    NUMBER_1_DOT_1(1.1),
+    
+    NUMBER_MINUS_1_DOT_2(-1.2);
+
+    private Double value;
+
+    EnumNumberEnum(Double value) {
+      this.value = value;
+    }
+
+    @JsonValue
+    public Double getValue() {
+      return value;
+    }
+
+    @Override
+    public String toString() {
+      return String.valueOf(value);
+    }
+
+    @JsonCreator
+    public static EnumNumberEnum fromValue(Double value) {
+      for (EnumNumberEnum b : EnumNumberEnum.values()) {
+        if (b.value.equals(value)) {
+          return b;
+        }
+      }
+      throw new IllegalArgumentException("Unexpected value '" + value + "'");
+    }
+  }
+
+  public static final String JSON_PROPERTY_ENUM_NUMBER = "enum_number";
+  private EnumNumberEnum enumNumber;
+
+  public static final String JSON_PROPERTY_OUTER_ENUM = "outerEnum";
+  private OuterEnum outerEnum;
+
+
+  public EnumTest enumString(EnumStringEnum enumString) {
+    
+    this.enumString = enumString;
+    return this;
+  }
+
+   /**
+   * Get enumString
+   * @return enumString
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_ENUM_STRING)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public EnumStringEnum getEnumString() {
+    return enumString;
+  }
+
+
+  public void setEnumString(EnumStringEnum enumString) {
+    this.enumString = enumString;
+  }
+
+
+  public EnumTest enumStringRequired(EnumStringRequiredEnum enumStringRequired) {
+    
+    this.enumStringRequired = enumStringRequired;
+    return this;
+  }
+
+   /**
+   * Get enumStringRequired
+   * @return enumStringRequired
+  **/
+  @ApiModelProperty(required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_ENUM_STRING_REQUIRED)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public EnumStringRequiredEnum getEnumStringRequired() {
+    return enumStringRequired;
+  }
+
+
+  public void setEnumStringRequired(EnumStringRequiredEnum enumStringRequired) {
+    this.enumStringRequired = enumStringRequired;
+  }
+
+
+  public EnumTest enumInteger(EnumIntegerEnum enumInteger) {
+    
+    this.enumInteger = enumInteger;
+    return this;
+  }
+
+   /**
+   * Get enumInteger
+   * @return enumInteger
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_ENUM_INTEGER)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public EnumIntegerEnum getEnumInteger() {
+    return enumInteger;
+  }
+
+
+  public void setEnumInteger(EnumIntegerEnum enumInteger) {
+    this.enumInteger = enumInteger;
+  }
+
+
+  public EnumTest enumNumber(EnumNumberEnum enumNumber) {
+    
+    this.enumNumber = enumNumber;
+    return this;
+  }
+
+   /**
+   * Get enumNumber
+   * @return enumNumber
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_ENUM_NUMBER)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public EnumNumberEnum getEnumNumber() {
+    return enumNumber;
+  }
+
+
+  public void setEnumNumber(EnumNumberEnum enumNumber) {
+    this.enumNumber = enumNumber;
+  }
+
+
+  public EnumTest outerEnum(OuterEnum outerEnum) {
+    
+    this.outerEnum = outerEnum;
+    return this;
+  }
+
+   /**
+   * Get outerEnum
+   * @return outerEnum
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_OUTER_ENUM)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public OuterEnum getOuterEnum() {
+    return outerEnum;
+  }
+
+
+  public void setOuterEnum(OuterEnum outerEnum) {
+    this.outerEnum = outerEnum;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    EnumTest enumTest = (EnumTest) o;
+    return Objects.equals(this.enumString, enumTest.enumString) &&
+        Objects.equals(this.enumStringRequired, enumTest.enumStringRequired) &&
+        Objects.equals(this.enumInteger, enumTest.enumInteger) &&
+        Objects.equals(this.enumNumber, enumTest.enumNumber) &&
+        Objects.equals(this.outerEnum, enumTest.outerEnum);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(enumString, enumStringRequired, enumInteger, enumNumber, outerEnum);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class EnumTest {\n");
+    sb.append("    enumString: ").append(toIndentedString(enumString)).append("\n");
+    sb.append("    enumStringRequired: ").append(toIndentedString(enumStringRequired)).append("\n");
+    sb.append("    enumInteger: ").append(toIndentedString(enumInteger)).append("\n");
+    sb.append("    enumNumber: ").append(toIndentedString(enumNumber)).append("\n");
+    sb.append("    outerEnum: ").append(toIndentedString(outerEnum)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/FileSchemaTestClass.java

@@ -0,0 +1,146 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.ArrayList;
+import java.util.List;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * FileSchemaTestClass
+ */
+@JsonPropertyOrder({
+  FileSchemaTestClass.JSON_PROPERTY_FILE,
+  FileSchemaTestClass.JSON_PROPERTY_FILES
+})
+@JsonTypeName("FileSchemaTestClass")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class FileSchemaTestClass {
+  public static final String JSON_PROPERTY_FILE = "file";
+  private java.io.File file;
+
+  public static final String JSON_PROPERTY_FILES = "files";
+  private List<java.io.File> files = null;
+
+
+  public FileSchemaTestClass file(java.io.File file) {
+    
+    this.file = file;
+    return this;
+  }
+
+   /**
+   * Get file
+   * @return file
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_FILE)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public java.io.File getFile() {
+    return file;
+  }
+
+
+  public void setFile(java.io.File file) {
+    this.file = file;
+  }
+
+
+  public FileSchemaTestClass files(List<java.io.File> files) {
+    
+    this.files = files;
+    return this;
+  }
+
+  public FileSchemaTestClass addFilesItem(java.io.File filesItem) {
+    if (this.files == null) {
+      this.files = new ArrayList<java.io.File>();
+    }
+    this.files.add(filesItem);
+    return this;
+  }
+
+   /**
+   * Get files
+   * @return files
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_FILES)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public List<java.io.File> getFiles() {
+    return files;
+  }
+
+
+  public void setFiles(List<java.io.File> files) {
+    this.files = files;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    FileSchemaTestClass fileSchemaTestClass = (FileSchemaTestClass) o;
+    return Objects.equals(this.file, fileSchemaTestClass.file) &&
+        Objects.equals(this.files, fileSchemaTestClass.files);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(file, files);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class FileSchemaTestClass {\n");
+    sb.append("    file: ").append(toIndentedString(file)).append("\n");
+    sb.append("    files: ").append(toIndentedString(files)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/FormatTest.java

@@ -0,0 +1,519 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.io.File;
+import java.math.BigDecimal;
+import java.util.UUID;
+import org.threeten.bp.LocalDate;
+import org.threeten.bp.OffsetDateTime;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * FormatTest
+ */
+@JsonPropertyOrder({
+  FormatTest.JSON_PROPERTY_INTEGER,
+  FormatTest.JSON_PROPERTY_INT32,
+  FormatTest.JSON_PROPERTY_INT64,
+  FormatTest.JSON_PROPERTY_NUMBER,
+  FormatTest.JSON_PROPERTY_FLOAT,
+  FormatTest.JSON_PROPERTY_DOUBLE,
+  FormatTest.JSON_PROPERTY_STRING,
+  FormatTest.JSON_PROPERTY_BYTE,
+  FormatTest.JSON_PROPERTY_BINARY,
+  FormatTest.JSON_PROPERTY_DATE,
+  FormatTest.JSON_PROPERTY_DATE_TIME,
+  FormatTest.JSON_PROPERTY_UUID,
+  FormatTest.JSON_PROPERTY_PASSWORD,
+  FormatTest.JSON_PROPERTY_BIG_DECIMAL
+})
+@JsonTypeName("format_test")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class FormatTest {
+  public static final String JSON_PROPERTY_INTEGER = "integer";
+  private Integer integer;
+
+  public static final String JSON_PROPERTY_INT32 = "int32";
+  private Integer int32;
+
+  public static final String JSON_PROPERTY_INT64 = "int64";
+  private Long int64;
+
+  public static final String JSON_PROPERTY_NUMBER = "number";
+  private BigDecimal number;
+
+  public static final String JSON_PROPERTY_FLOAT = "float";
+  private Float _float;
+
+  public static final String JSON_PROPERTY_DOUBLE = "double";
+  private Double _double;
+
+  public static final String JSON_PROPERTY_STRING = "string";
+  private String string;
+
+  public static final String JSON_PROPERTY_BYTE = "byte";
+  private byte[] _byte;
+
+  public static final String JSON_PROPERTY_BINARY = "binary";
+  private File binary;
+
+  public static final String JSON_PROPERTY_DATE = "date";
+  private LocalDate date;
+
+  public static final String JSON_PROPERTY_DATE_TIME = "dateTime";
+  private OffsetDateTime dateTime;
+
+  public static final String JSON_PROPERTY_UUID = "uuid";
+  private UUID uuid;
+
+  public static final String JSON_PROPERTY_PASSWORD = "password";
+  private String password;
+
+  public static final String JSON_PROPERTY_BIG_DECIMAL = "BigDecimal";
+  private BigDecimal bigDecimal;
+
+
+  public FormatTest integer(Integer integer) {
+    
+    this.integer = integer;
+    return this;
+  }
+
+   /**
+   * Get integer
+   * minimum: 10
+   * maximum: 100
+   * @return integer
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_INTEGER)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Integer getInteger() {
+    return integer;
+  }
+
+
+  public void setInteger(Integer integer) {
+    this.integer = integer;
+  }
+
+
+  public FormatTest int32(Integer int32) {
+    
+    this.int32 = int32;
+    return this;
+  }
+
+   /**
+   * Get int32
+   * minimum: 20
+   * maximum: 200
+   * @return int32
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_INT32)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Integer getInt32() {
+    return int32;
+  }
+
+
+  public void setInt32(Integer int32) {
+    this.int32 = int32;
+  }
+
+
+  public FormatTest int64(Long int64) {
+    
+    this.int64 = int64;
+    return this;
+  }
+
+   /**
+   * Get int64
+   * @return int64
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_INT64)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Long getInt64() {
+    return int64;
+  }
+
+
+  public void setInt64(Long int64) {
+    this.int64 = int64;
+  }
+
+
+  public FormatTest number(BigDecimal number) {
+    
+    this.number = number;
+    return this;
+  }
+
+   /**
+   * Get number
+   * minimum: 32.1
+   * maximum: 543.2
+   * @return number
+  **/
+  @ApiModelProperty(required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_NUMBER)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public BigDecimal getNumber() {
+    return number;
+  }
+
+
+  public void setNumber(BigDecimal number) {
+    this.number = number;
+  }
+
+
+  public FormatTest _float(Float _float) {
+    
+    this._float = _float;
+    return this;
+  }
+
+   /**
+   * Get _float
+   * minimum: 54.3
+   * maximum: 987.6
+   * @return _float
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_FLOAT)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Float getFloat() {
+    return _float;
+  }
+
+
+  public void setFloat(Float _float) {
+    this._float = _float;
+  }
+
+
+  public FormatTest _double(Double _double) {
+    
+    this._double = _double;
+    return this;
+  }
+
+   /**
+   * Get _double
+   * minimum: 67.8
+   * maximum: 123.4
+   * @return _double
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_DOUBLE)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Double getDouble() {
+    return _double;
+  }
+
+
+  public void setDouble(Double _double) {
+    this._double = _double;
+  }
+
+
+  public FormatTest string(String string) {
+    
+    this.string = string;
+    return this;
+  }
+
+   /**
+   * Get string
+   * @return string
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_STRING)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getString() {
+    return string;
+  }
+
+
+  public void setString(String string) {
+    this.string = string;
+  }
+
+
+  public FormatTest _byte(byte[] _byte) {
+    
+    this._byte = _byte;
+    return this;
+  }
+
+   /**
+   * Get _byte
+   * @return _byte
+  **/
+  @ApiModelProperty(required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_BYTE)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public byte[] getByte() {
+    return _byte;
+  }
+
+
+  public void setByte(byte[] _byte) {
+    this._byte = _byte;
+  }
+
+
+  public FormatTest binary(File binary) {
+    
+    this.binary = binary;
+    return this;
+  }
+
+   /**
+   * Get binary
+   * @return binary
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_BINARY)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public File getBinary() {
+    return binary;
+  }
+
+
+  public void setBinary(File binary) {
+    this.binary = binary;
+  }
+
+
+  public FormatTest date(LocalDate date) {
+    
+    this.date = date;
+    return this;
+  }
+
+   /**
+   * Get date
+   * @return date
+  **/
+  @ApiModelProperty(required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_DATE)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public LocalDate getDate() {
+    return date;
+  }
+
+
+  public void setDate(LocalDate date) {
+    this.date = date;
+  }
+
+
+  public FormatTest dateTime(OffsetDateTime dateTime) {
+    
+    this.dateTime = dateTime;
+    return this;
+  }
+
+   /**
+   * Get dateTime
+   * @return dateTime
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_DATE_TIME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public OffsetDateTime getDateTime() {
+    return dateTime;
+  }
+
+
+  public void setDateTime(OffsetDateTime dateTime) {
+    this.dateTime = dateTime;
+  }
+
+
+  public FormatTest uuid(UUID uuid) {
+    
+    this.uuid = uuid;
+    return this;
+  }
+
+   /**
+   * Get uuid
+   * @return uuid
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(example = "72f98069-206d-4f12-9f12-3d1e525a8e84", value = "")
+  @JsonProperty(JSON_PROPERTY_UUID)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public UUID getUuid() {
+    return uuid;
+  }
+
+
+  public void setUuid(UUID uuid) {
+    this.uuid = uuid;
+  }
+
+
+  public FormatTest password(String password) {
+    
+    this.password = password;
+    return this;
+  }
+
+   /**
+   * Get password
+   * @return password
+  **/
+  @ApiModelProperty(required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_PASSWORD)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public String getPassword() {
+    return password;
+  }
+
+
+  public void setPassword(String password) {
+    this.password = password;
+  }
+
+
+  public FormatTest bigDecimal(BigDecimal bigDecimal) {
+    
+    this.bigDecimal = bigDecimal;
+    return this;
+  }
+
+   /**
+   * Get bigDecimal
+   * @return bigDecimal
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_BIG_DECIMAL)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public BigDecimal getBigDecimal() {
+    return bigDecimal;
+  }
+
+
+  public void setBigDecimal(BigDecimal bigDecimal) {
+    this.bigDecimal = bigDecimal;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    FormatTest formatTest = (FormatTest) o;
+    return Objects.equals(this.integer, formatTest.integer) &&
+        Objects.equals(this.int32, formatTest.int32) &&
+        Objects.equals(this.int64, formatTest.int64) &&
+        Objects.equals(this.number, formatTest.number) &&
+        Objects.equals(this._float, formatTest._float) &&
+        Objects.equals(this._double, formatTest._double) &&
+        Objects.equals(this.string, formatTest.string) &&
+        Arrays.equals(this._byte, formatTest._byte) &&
+        Objects.equals(this.binary, formatTest.binary) &&
+        Objects.equals(this.date, formatTest.date) &&
+        Objects.equals(this.dateTime, formatTest.dateTime) &&
+        Objects.equals(this.uuid, formatTest.uuid) &&
+        Objects.equals(this.password, formatTest.password) &&
+        Objects.equals(this.bigDecimal, formatTest.bigDecimal);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(integer, int32, int64, number, _float, _double, string, Arrays.hashCode(_byte), binary, date, dateTime, uuid, password, bigDecimal);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class FormatTest {\n");
+    sb.append("    integer: ").append(toIndentedString(integer)).append("\n");
+    sb.append("    int32: ").append(toIndentedString(int32)).append("\n");
+    sb.append("    int64: ").append(toIndentedString(int64)).append("\n");
+    sb.append("    number: ").append(toIndentedString(number)).append("\n");
+    sb.append("    _float: ").append(toIndentedString(_float)).append("\n");
+    sb.append("    _double: ").append(toIndentedString(_double)).append("\n");
+    sb.append("    string: ").append(toIndentedString(string)).append("\n");
+    sb.append("    _byte: ").append(toIndentedString(_byte)).append("\n");
+    sb.append("    binary: ").append(toIndentedString(binary)).append("\n");
+    sb.append("    date: ").append(toIndentedString(date)).append("\n");
+    sb.append("    dateTime: ").append(toIndentedString(dateTime)).append("\n");
+    sb.append("    uuid: ").append(toIndentedString(uuid)).append("\n");
+    sb.append("    password: ").append(toIndentedString(password)).append("\n");
+    sb.append("    bigDecimal: ").append(toIndentedString(bigDecimal)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/HasOnlyReadOnly.java

@@ -0,0 +1,118 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * HasOnlyReadOnly
+ */
+@JsonPropertyOrder({
+  HasOnlyReadOnly.JSON_PROPERTY_BAR,
+  HasOnlyReadOnly.JSON_PROPERTY_FOO
+})
+@JsonTypeName("hasOnlyReadOnly")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class HasOnlyReadOnly {
+  public static final String JSON_PROPERTY_BAR = "bar";
+  private String bar;
+
+  public static final String JSON_PROPERTY_FOO = "foo";
+  private String foo;
+
+
+   /**
+   * Get bar
+   * @return bar
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_BAR)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getBar() {
+    return bar;
+  }
+
+
+
+
+   /**
+   * Get foo
+   * @return foo
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_FOO)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getFoo() {
+    return foo;
+  }
+
+
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    HasOnlyReadOnly hasOnlyReadOnly = (HasOnlyReadOnly) o;
+    return Objects.equals(this.bar, hasOnlyReadOnly.bar) &&
+        Objects.equals(this.foo, hasOnlyReadOnly.foo);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(bar, foo);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class HasOnlyReadOnly {\n");
+    sb.append("    bar: ").append(toIndentedString(bar)).append("\n");
+    sb.append("    foo: ").append(toIndentedString(foo)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/MapTest.java

@@ -0,0 +1,268 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * MapTest
+ */
+@JsonPropertyOrder({
+  MapTest.JSON_PROPERTY_MAP_MAP_OF_STRING,
+  MapTest.JSON_PROPERTY_MAP_OF_ENUM_STRING,
+  MapTest.JSON_PROPERTY_DIRECT_MAP,
+  MapTest.JSON_PROPERTY_INDIRECT_MAP
+})
+@JsonTypeName("MapTest")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class MapTest {
+  public static final String JSON_PROPERTY_MAP_MAP_OF_STRING = "map_map_of_string";
+  private Map<String, Map<String, String>> mapMapOfString = null;
+
+  /**
+   * Gets or Sets inner
+   */
+  public enum InnerEnum {
+    UPPER("UPPER"),
+    
+    LOWER("lower");
+
+    private String value;
+
+    InnerEnum(String value) {
+      this.value = value;
+    }
+
+    @JsonValue
+    public String getValue() {
+      return value;
+    }
+
+    @Override
+    public String toString() {
+      return String.valueOf(value);
+    }
+
+    @JsonCreator
+    public static InnerEnum fromValue(String value) {
+      for (InnerEnum b : InnerEnum.values()) {
+        if (b.value.equals(value)) {
+          return b;
+        }
+      }
+      throw new IllegalArgumentException("Unexpected value '" + value + "'");
+    }
+  }
+
+  public static final String JSON_PROPERTY_MAP_OF_ENUM_STRING = "map_of_enum_string";
+  private Map<String, InnerEnum> mapOfEnumString = null;
+
+  public static final String JSON_PROPERTY_DIRECT_MAP = "direct_map";
+  private Map<String, Boolean> directMap = null;
+
+  public static final String JSON_PROPERTY_INDIRECT_MAP = "indirect_map";
+  private Map<String, Boolean> indirectMap = null;
+
+
+  public MapTest mapMapOfString(Map<String, Map<String, String>> mapMapOfString) {
+    
+    this.mapMapOfString = mapMapOfString;
+    return this;
+  }
+
+  public MapTest putMapMapOfStringItem(String key, Map<String, String> mapMapOfStringItem) {
+    if (this.mapMapOfString == null) {
+      this.mapMapOfString = new HashMap<String, Map<String, String>>();
+    }
+    this.mapMapOfString.put(key, mapMapOfStringItem);
+    return this;
+  }
+
+   /**
+   * Get mapMapOfString
+   * @return mapMapOfString
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_MAP_MAP_OF_STRING)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Map<String, Map<String, String>> getMapMapOfString() {
+    return mapMapOfString;
+  }
+
+
+  public void setMapMapOfString(Map<String, Map<String, String>> mapMapOfString) {
+    this.mapMapOfString = mapMapOfString;
+  }
+
+
+  public MapTest mapOfEnumString(Map<String, InnerEnum> mapOfEnumString) {
+    
+    this.mapOfEnumString = mapOfEnumString;
+    return this;
+  }
+
+  public MapTest putMapOfEnumStringItem(String key, InnerEnum mapOfEnumStringItem) {
+    if (this.mapOfEnumString == null) {
+      this.mapOfEnumString = new HashMap<String, InnerEnum>();
+    }
+    this.mapOfEnumString.put(key, mapOfEnumStringItem);
+    return this;
+  }
+
+   /**
+   * Get mapOfEnumString
+   * @return mapOfEnumString
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_MAP_OF_ENUM_STRING)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Map<String, InnerEnum> getMapOfEnumString() {
+    return mapOfEnumString;
+  }
+
+
+  public void setMapOfEnumString(Map<String, InnerEnum> mapOfEnumString) {
+    this.mapOfEnumString = mapOfEnumString;
+  }
+
+
+  public MapTest directMap(Map<String, Boolean> directMap) {
+    
+    this.directMap = directMap;
+    return this;
+  }
+
+  public MapTest putDirectMapItem(String key, Boolean directMapItem) {
+    if (this.directMap == null) {
+      this.directMap = new HashMap<String, Boolean>();
+    }
+    this.directMap.put(key, directMapItem);
+    return this;
+  }
+
+   /**
+   * Get directMap
+   * @return directMap
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_DIRECT_MAP)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Map<String, Boolean> getDirectMap() {
+    return directMap;
+  }
+
+
+  public void setDirectMap(Map<String, Boolean> directMap) {
+    this.directMap = directMap;
+  }
+
+
+  public MapTest indirectMap(Map<String, Boolean> indirectMap) {
+    
+    this.indirectMap = indirectMap;
+    return this;
+  }
+
+  public MapTest putIndirectMapItem(String key, Boolean indirectMapItem) {
+    if (this.indirectMap == null) {
+      this.indirectMap = new HashMap<String, Boolean>();
+    }
+    this.indirectMap.put(key, indirectMapItem);
+    return this;
+  }
+
+   /**
+   * Get indirectMap
+   * @return indirectMap
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_INDIRECT_MAP)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Map<String, Boolean> getIndirectMap() {
+    return indirectMap;
+  }
+
+
+  public void setIndirectMap(Map<String, Boolean> indirectMap) {
+    this.indirectMap = indirectMap;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    MapTest mapTest = (MapTest) o;
+    return Objects.equals(this.mapMapOfString, mapTest.mapMapOfString) &&
+        Objects.equals(this.mapOfEnumString, mapTest.mapOfEnumString) &&
+        Objects.equals(this.directMap, mapTest.directMap) &&
+        Objects.equals(this.indirectMap, mapTest.indirectMap);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(mapMapOfString, mapOfEnumString, directMap, indirectMap);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class MapTest {\n");
+    sb.append("    mapMapOfString: ").append(toIndentedString(mapMapOfString)).append("\n");
+    sb.append("    mapOfEnumString: ").append(toIndentedString(mapOfEnumString)).append("\n");
+    sb.append("    directMap: ").append(toIndentedString(directMap)).append("\n");
+    sb.append("    indirectMap: ").append(toIndentedString(indirectMap)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/MixedPropertiesAndAdditionalPropertiesClass.java

@@ -0,0 +1,181 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+import org.openapitools.client.model.Animal;
+import org.threeten.bp.OffsetDateTime;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * MixedPropertiesAndAdditionalPropertiesClass
+ */
+@JsonPropertyOrder({
+  MixedPropertiesAndAdditionalPropertiesClass.JSON_PROPERTY_UUID,
+  MixedPropertiesAndAdditionalPropertiesClass.JSON_PROPERTY_DATE_TIME,
+  MixedPropertiesAndAdditionalPropertiesClass.JSON_PROPERTY_MAP
+})
+@JsonTypeName("MixedPropertiesAndAdditionalPropertiesClass")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class MixedPropertiesAndAdditionalPropertiesClass {
+  public static final String JSON_PROPERTY_UUID = "uuid";
+  private UUID uuid;
+
+  public static final String JSON_PROPERTY_DATE_TIME = "dateTime";
+  private OffsetDateTime dateTime;
+
+  public static final String JSON_PROPERTY_MAP = "map";
+  private Map<String, Animal> map = null;
+
+
+  public MixedPropertiesAndAdditionalPropertiesClass uuid(UUID uuid) {
+    
+    this.uuid = uuid;
+    return this;
+  }
+
+   /**
+   * Get uuid
+   * @return uuid
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_UUID)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public UUID getUuid() {
+    return uuid;
+  }
+
+
+  public void setUuid(UUID uuid) {
+    this.uuid = uuid;
+  }
+
+
+  public MixedPropertiesAndAdditionalPropertiesClass dateTime(OffsetDateTime dateTime) {
+    
+    this.dateTime = dateTime;
+    return this;
+  }
+
+   /**
+   * Get dateTime
+   * @return dateTime
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_DATE_TIME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public OffsetDateTime getDateTime() {
+    return dateTime;
+  }
+
+
+  public void setDateTime(OffsetDateTime dateTime) {
+    this.dateTime = dateTime;
+  }
+
+
+  public MixedPropertiesAndAdditionalPropertiesClass map(Map<String, Animal> map) {
+    
+    this.map = map;
+    return this;
+  }
+
+  public MixedPropertiesAndAdditionalPropertiesClass putMapItem(String key, Animal mapItem) {
+    if (this.map == null) {
+      this.map = new HashMap<String, Animal>();
+    }
+    this.map.put(key, mapItem);
+    return this;
+  }
+
+   /**
+   * Get map
+   * @return map
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_MAP)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Map<String, Animal> getMap() {
+    return map;
+  }
+
+
+  public void setMap(Map<String, Animal> map) {
+    this.map = map;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    MixedPropertiesAndAdditionalPropertiesClass mixedPropertiesAndAdditionalPropertiesClass = (MixedPropertiesAndAdditionalPropertiesClass) o;
+    return Objects.equals(this.uuid, mixedPropertiesAndAdditionalPropertiesClass.uuid) &&
+        Objects.equals(this.dateTime, mixedPropertiesAndAdditionalPropertiesClass.dateTime) &&
+        Objects.equals(this.map, mixedPropertiesAndAdditionalPropertiesClass.map);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(uuid, dateTime, map);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class MixedPropertiesAndAdditionalPropertiesClass {\n");
+    sb.append("    uuid: ").append(toIndentedString(uuid)).append("\n");
+    sb.append("    dateTime: ").append(toIndentedString(dateTime)).append("\n");
+    sb.append("    map: ").append(toIndentedString(map)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/Model200Response.java

@@ -0,0 +1,137 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * Model for testing model name starting with number
+ */
+@ApiModel(description = "Model for testing model name starting with number")
+@JsonPropertyOrder({
+  Model200Response.JSON_PROPERTY_NAME,
+  Model200Response.JSON_PROPERTY_PROPERTY_CLASS
+})
+@JsonTypeName("200_response")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Model200Response {
+  public static final String JSON_PROPERTY_NAME = "name";
+  private Integer name;
+
+  public static final String JSON_PROPERTY_PROPERTY_CLASS = "class";
+  private String propertyClass;
+
+
+  public Model200Response name(Integer name) {
+    
+    this.name = name;
+    return this;
+  }
+
+   /**
+   * Get name
+   * @return name
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Integer getName() {
+    return name;
+  }
+
+
+  public void setName(Integer name) {
+    this.name = name;
+  }
+
+
+  public Model200Response propertyClass(String propertyClass) {
+    
+    this.propertyClass = propertyClass;
+    return this;
+  }
+
+   /**
+   * Get propertyClass
+   * @return propertyClass
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_PROPERTY_CLASS)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getPropertyClass() {
+    return propertyClass;
+  }
+
+
+  public void setPropertyClass(String propertyClass) {
+    this.propertyClass = propertyClass;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    Model200Response _200response = (Model200Response) o;
+    return Objects.equals(this.name, _200response.name) &&
+        Objects.equals(this.propertyClass, _200response.propertyClass);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(name, propertyClass);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class Model200Response {\n");
+    sb.append("    name: ").append(toIndentedString(name)).append("\n");
+    sb.append("    propertyClass: ").append(toIndentedString(propertyClass)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/ModelApiResponse.java

@@ -0,0 +1,167 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * ModelApiResponse
+ */
+@JsonPropertyOrder({
+  ModelApiResponse.JSON_PROPERTY_CODE,
+  ModelApiResponse.JSON_PROPERTY_TYPE,
+  ModelApiResponse.JSON_PROPERTY_MESSAGE
+})
+@JsonTypeName("ApiResponse")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class ModelApiResponse {
+  public static final String JSON_PROPERTY_CODE = "code";
+  private Integer code;
+
+  public static final String JSON_PROPERTY_TYPE = "type";
+  private String type;
+
+  public static final String JSON_PROPERTY_MESSAGE = "message";
+  private String message;
+
+
+  public ModelApiResponse code(Integer code) {
+    
+    this.code = code;
+    return this;
+  }
+
+   /**
+   * Get code
+   * @return code
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_CODE)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Integer getCode() {
+    return code;
+  }
+
+
+  public void setCode(Integer code) {
+    this.code = code;
+  }
+
+
+  public ModelApiResponse type(String type) {
+    
+    this.type = type;
+    return this;
+  }
+
+   /**
+   * Get type
+   * @return type
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_TYPE)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getType() {
+    return type;
+  }
+
+
+  public void setType(String type) {
+    this.type = type;
+  }
+
+
+  public ModelApiResponse message(String message) {
+    
+    this.message = message;
+    return this;
+  }
+
+   /**
+   * Get message
+   * @return message
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_MESSAGE)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getMessage() {
+    return message;
+  }
+
+
+  public void setMessage(String message) {
+    this.message = message;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    ModelApiResponse _apiResponse = (ModelApiResponse) o;
+    return Objects.equals(this.code, _apiResponse.code) &&
+        Objects.equals(this.type, _apiResponse.type) &&
+        Objects.equals(this.message, _apiResponse.message);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(code, type, message);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class ModelApiResponse {\n");
+    sb.append("    code: ").append(toIndentedString(code)).append("\n");
+    sb.append("    type: ").append(toIndentedString(type)).append("\n");
+    sb.append("    message: ").append(toIndentedString(message)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/ModelReturn.java

@@ -0,0 +1,106 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * Model for testing reserved words
+ */
+@ApiModel(description = "Model for testing reserved words")
+@JsonPropertyOrder({
+  ModelReturn.JSON_PROPERTY_RETURN
+})
+@JsonTypeName("Return")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class ModelReturn {
+  public static final String JSON_PROPERTY_RETURN = "return";
+  private Integer _return;
+
+
+  public ModelReturn _return(Integer _return) {
+    
+    this._return = _return;
+    return this;
+  }
+
+   /**
+   * Get _return
+   * @return _return
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_RETURN)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Integer getReturn() {
+    return _return;
+  }
+
+
+  public void setReturn(Integer _return) {
+    this._return = _return;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    ModelReturn _return = (ModelReturn) o;
+    return Objects.equals(this._return, _return._return);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(_return);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class ModelReturn {\n");
+    sb.append("    _return: ").append(toIndentedString(_return)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/Name.java

@@ -0,0 +1,180 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * Model for testing model name same as property name
+ */
+@ApiModel(description = "Model for testing model name same as property name")
+@JsonPropertyOrder({
+  Name.JSON_PROPERTY_NAME,
+  Name.JSON_PROPERTY_SNAKE_CASE,
+  Name.JSON_PROPERTY_PROPERTY,
+  Name.JSON_PROPERTY_123NUMBER
+})
+@JsonTypeName("Name")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Name {
+  public static final String JSON_PROPERTY_NAME = "name";
+  private Integer name;
+
+  public static final String JSON_PROPERTY_SNAKE_CASE = "snake_case";
+  private Integer snakeCase;
+
+  public static final String JSON_PROPERTY_PROPERTY = "property";
+  private String property;
+
+  public static final String JSON_PROPERTY_123NUMBER = "123Number";
+  private Integer _123number;
+
+
+  public Name name(Integer name) {
+    
+    this.name = name;
+    return this;
+  }
+
+   /**
+   * Get name
+   * @return name
+  **/
+  @ApiModelProperty(required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public Integer getName() {
+    return name;
+  }
+
+
+  public void setName(Integer name) {
+    this.name = name;
+  }
+
+
+   /**
+   * Get snakeCase
+   * @return snakeCase
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_SNAKE_CASE)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Integer getSnakeCase() {
+    return snakeCase;
+  }
+
+
+
+
+  public Name property(String property) {
+    
+    this.property = property;
+    return this;
+  }
+
+   /**
+   * Get property
+   * @return property
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_PROPERTY)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getProperty() {
+    return property;
+  }
+
+
+  public void setProperty(String property) {
+    this.property = property;
+  }
+
+
+   /**
+   * Get _123number
+   * @return _123number
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_123NUMBER)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Integer get123number() {
+    return _123number;
+  }
+
+
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    Name name = (Name) o;
+    return Objects.equals(this.name, name.name) &&
+        Objects.equals(this.snakeCase, name.snakeCase) &&
+        Objects.equals(this.property, name.property) &&
+        Objects.equals(this._123number, name._123number);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(name, snakeCase, property, _123number);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class Name {\n");
+    sb.append("    name: ").append(toIndentedString(name)).append("\n");
+    sb.append("    snakeCase: ").append(toIndentedString(snakeCase)).append("\n");
+    sb.append("    property: ").append(toIndentedString(property)).append("\n");
+    sb.append("    _123number: ").append(toIndentedString(_123number)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/NumberOnly.java

@@ -0,0 +1,106 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.math.BigDecimal;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * NumberOnly
+ */
+@JsonPropertyOrder({
+  NumberOnly.JSON_PROPERTY_JUST_NUMBER
+})
+@JsonTypeName("NumberOnly")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class NumberOnly {
+  public static final String JSON_PROPERTY_JUST_NUMBER = "JustNumber";
+  private BigDecimal justNumber;
+
+
+  public NumberOnly justNumber(BigDecimal justNumber) {
+    
+    this.justNumber = justNumber;
+    return this;
+  }
+
+   /**
+   * Get justNumber
+   * @return justNumber
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_JUST_NUMBER)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public BigDecimal getJustNumber() {
+    return justNumber;
+  }
+
+
+  public void setJustNumber(BigDecimal justNumber) {
+    this.justNumber = justNumber;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    NumberOnly numberOnly = (NumberOnly) o;
+    return Objects.equals(this.justNumber, numberOnly.justNumber);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(justNumber);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class NumberOnly {\n");
+    sb.append("    justNumber: ").append(toIndentedString(justNumber)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/Order.java

@@ -0,0 +1,298 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.threeten.bp.OffsetDateTime;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * Order
+ */
+@JsonPropertyOrder({
+  Order.JSON_PROPERTY_ID,
+  Order.JSON_PROPERTY_PET_ID,
+  Order.JSON_PROPERTY_QUANTITY,
+  Order.JSON_PROPERTY_SHIP_DATE,
+  Order.JSON_PROPERTY_STATUS,
+  Order.JSON_PROPERTY_COMPLETE
+})
+@JsonTypeName("Order")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Order {
+  public static final String JSON_PROPERTY_ID = "id";
+  private Long id;
+
+  public static final String JSON_PROPERTY_PET_ID = "petId";
+  private Long petId;
+
+  public static final String JSON_PROPERTY_QUANTITY = "quantity";
+  private Integer quantity;
+
+  public static final String JSON_PROPERTY_SHIP_DATE = "shipDate";
+  private OffsetDateTime shipDate;
+
+  /**
+   * Order Status
+   */
+  public enum StatusEnum {
+    PLACED("placed"),
+    
+    APPROVED("approved"),
+    
+    DELIVERED("delivered");
+
+    private String value;
+
+    StatusEnum(String value) {
+      this.value = value;
+    }
+
+    @JsonValue
+    public String getValue() {
+      return value;
+    }
+
+    @Override
+    public String toString() {
+      return String.valueOf(value);
+    }
+
+    @JsonCreator
+    public static StatusEnum fromValue(String value) {
+      for (StatusEnum b : StatusEnum.values()) {
+        if (b.value.equals(value)) {
+          return b;
+        }
+      }
+      throw new IllegalArgumentException("Unexpected value '" + value + "'");
+    }
+  }
+
+  public static final String JSON_PROPERTY_STATUS = "status";
+  private StatusEnum status;
+
+  public static final String JSON_PROPERTY_COMPLETE = "complete";
+  private Boolean complete = false;
+
+
+  public Order id(Long id) {
+    
+    this.id = id;
+    return this;
+  }
+
+   /**
+   * Get id
+   * @return id
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_ID)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Long getId() {
+    return id;
+  }
+
+
+  public void setId(Long id) {
+    this.id = id;
+  }
+
+
+  public Order petId(Long petId) {
+    
+    this.petId = petId;
+    return this;
+  }
+
+   /**
+   * Get petId
+   * @return petId
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_PET_ID)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Long getPetId() {
+    return petId;
+  }
+
+
+  public void setPetId(Long petId) {
+    this.petId = petId;
+  }
+
+
+  public Order quantity(Integer quantity) {
+    
+    this.quantity = quantity;
+    return this;
+  }
+
+   /**
+   * Get quantity
+   * @return quantity
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_QUANTITY)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Integer getQuantity() {
+    return quantity;
+  }
+
+
+  public void setQuantity(Integer quantity) {
+    this.quantity = quantity;
+  }
+
+
+  public Order shipDate(OffsetDateTime shipDate) {
+    
+    this.shipDate = shipDate;
+    return this;
+  }
+
+   /**
+   * Get shipDate
+   * @return shipDate
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_SHIP_DATE)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public OffsetDateTime getShipDate() {
+    return shipDate;
+  }
+
+
+  public void setShipDate(OffsetDateTime shipDate) {
+    this.shipDate = shipDate;
+  }
+
+
+  public Order status(StatusEnum status) {
+    
+    this.status = status;
+    return this;
+  }
+
+   /**
+   * Order Status
+   * @return status
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "Order Status")
+  @JsonProperty(JSON_PROPERTY_STATUS)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public StatusEnum getStatus() {
+    return status;
+  }
+
+
+  public void setStatus(StatusEnum status) {
+    this.status = status;
+  }
+
+
+  public Order complete(Boolean complete) {
+    
+    this.complete = complete;
+    return this;
+  }
+
+   /**
+   * Get complete
+   * @return complete
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_COMPLETE)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Boolean isComplete() {
+    return complete;
+  }
+
+
+  public void setComplete(Boolean complete) {
+    this.complete = complete;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    Order order = (Order) o;
+    return Objects.equals(this.id, order.id) &&
+        Objects.equals(this.petId, order.petId) &&
+        Objects.equals(this.quantity, order.quantity) &&
+        Objects.equals(this.shipDate, order.shipDate) &&
+        Objects.equals(this.status, order.status) &&
+        Objects.equals(this.complete, order.complete);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(id, petId, quantity, shipDate, status, complete);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class Order {\n");
+    sb.append("    id: ").append(toIndentedString(id)).append("\n");
+    sb.append("    petId: ").append(toIndentedString(petId)).append("\n");
+    sb.append("    quantity: ").append(toIndentedString(quantity)).append("\n");
+    sb.append("    shipDate: ").append(toIndentedString(shipDate)).append("\n");
+    sb.append("    status: ").append(toIndentedString(status)).append("\n");
+    sb.append("    complete: ").append(toIndentedString(complete)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/OuterComposite.java

@@ -0,0 +1,168 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.math.BigDecimal;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * OuterComposite
+ */
+@JsonPropertyOrder({
+  OuterComposite.JSON_PROPERTY_MY_NUMBER,
+  OuterComposite.JSON_PROPERTY_MY_STRING,
+  OuterComposite.JSON_PROPERTY_MY_BOOLEAN
+})
+@JsonTypeName("OuterComposite")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class OuterComposite {
+  public static final String JSON_PROPERTY_MY_NUMBER = "my_number";
+  private BigDecimal myNumber;
+
+  public static final String JSON_PROPERTY_MY_STRING = "my_string";
+  private String myString;
+
+  public static final String JSON_PROPERTY_MY_BOOLEAN = "my_boolean";
+  private Boolean myBoolean;
+
+
+  public OuterComposite myNumber(BigDecimal myNumber) {
+    
+    this.myNumber = myNumber;
+    return this;
+  }
+
+   /**
+   * Get myNumber
+   * @return myNumber
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_MY_NUMBER)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public BigDecimal getMyNumber() {
+    return myNumber;
+  }
+
+
+  public void setMyNumber(BigDecimal myNumber) {
+    this.myNumber = myNumber;
+  }
+
+
+  public OuterComposite myString(String myString) {
+    
+    this.myString = myString;
+    return this;
+  }
+
+   /**
+   * Get myString
+   * @return myString
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_MY_STRING)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getMyString() {
+    return myString;
+  }
+
+
+  public void setMyString(String myString) {
+    this.myString = myString;
+  }
+
+
+  public OuterComposite myBoolean(Boolean myBoolean) {
+    
+    this.myBoolean = myBoolean;
+    return this;
+  }
+
+   /**
+   * Get myBoolean
+   * @return myBoolean
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_MY_BOOLEAN)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Boolean isMyBoolean() {
+    return myBoolean;
+  }
+
+
+  public void setMyBoolean(Boolean myBoolean) {
+    this.myBoolean = myBoolean;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    OuterComposite outerComposite = (OuterComposite) o;
+    return Objects.equals(this.myNumber, outerComposite.myNumber) &&
+        Objects.equals(this.myString, outerComposite.myString) &&
+        Objects.equals(this.myBoolean, outerComposite.myBoolean);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(myNumber, myString, myBoolean);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class OuterComposite {\n");
+    sb.append("    myNumber: ").append(toIndentedString(myNumber)).append("\n");
+    sb.append("    myString: ").append(toIndentedString(myString)).append("\n");
+    sb.append("    myBoolean: ").append(toIndentedString(myBoolean)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/OuterEnum.java

@@ -0,0 +1,60 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonValue;
+
+/**
+ * Gets or Sets OuterEnum
+ */
+public enum OuterEnum {
+  
+  PLACED("placed"),
+  
+  APPROVED("approved"),
+  
+  DELIVERED("delivered");
+
+  private String value;
+
+  OuterEnum(String value) {
+    this.value = value;
+  }
+
+  @JsonValue
+  public String getValue() {
+    return value;
+  }
+
+  @Override
+  public String toString() {
+    return String.valueOf(value);
+  }
+
+  @JsonCreator
+  public static OuterEnum fromValue(String value) {
+    for (OuterEnum b : OuterEnum.values()) {
+      if (b.value.equals(value)) {
+        return b;
+      }
+    }
+    throw new IllegalArgumentException("Unexpected value '" + value + "'");
+  }
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/Pet.java

@@ -0,0 +1,314 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.ArrayList;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Set;
+import org.openapitools.client.model.Category;
+import org.openapitools.client.model.Tag;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * Pet
+ */
+@JsonPropertyOrder({
+  Pet.JSON_PROPERTY_ID,
+  Pet.JSON_PROPERTY_CATEGORY,
+  Pet.JSON_PROPERTY_NAME,
+  Pet.JSON_PROPERTY_PHOTO_URLS,
+  Pet.JSON_PROPERTY_TAGS,
+  Pet.JSON_PROPERTY_STATUS
+})
+@JsonTypeName("Pet")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Pet {
+  public static final String JSON_PROPERTY_ID = "id";
+  private Long id;
+
+  public static final String JSON_PROPERTY_CATEGORY = "category";
+  private Category category;
+
+  public static final String JSON_PROPERTY_NAME = "name";
+  private String name;
+
+  public static final String JSON_PROPERTY_PHOTO_URLS = "photoUrls";
+  private Set<String> photoUrls = new LinkedHashSet<String>();
+
+  public static final String JSON_PROPERTY_TAGS = "tags";
+  private List<Tag> tags = null;
+
+  /**
+   * pet status in the store
+   */
+  public enum StatusEnum {
+    AVAILABLE("available"),
+    
+    PENDING("pending"),
+    
+    SOLD("sold");
+
+    private String value;
+
+    StatusEnum(String value) {
+      this.value = value;
+    }
+
+    @JsonValue
+    public String getValue() {
+      return value;
+    }
+
+    @Override
+    public String toString() {
+      return String.valueOf(value);
+    }
+
+    @JsonCreator
+    public static StatusEnum fromValue(String value) {
+      for (StatusEnum b : StatusEnum.values()) {
+        if (b.value.equals(value)) {
+          return b;
+        }
+      }
+      throw new IllegalArgumentException("Unexpected value '" + value + "'");
+    }
+  }
+
+  public static final String JSON_PROPERTY_STATUS = "status";
+  private StatusEnum status;
+
+
+  public Pet id(Long id) {
+    
+    this.id = id;
+    return this;
+  }
+
+   /**
+   * Get id
+   * @return id
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_ID)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Long getId() {
+    return id;
+  }
+
+
+  public void setId(Long id) {
+    this.id = id;
+  }
+
+
+  public Pet category(Category category) {
+    
+    this.category = category;
+    return this;
+  }
+
+   /**
+   * Get category
+   * @return category
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_CATEGORY)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Category getCategory() {
+    return category;
+  }
+
+
+  public void setCategory(Category category) {
+    this.category = category;
+  }
+
+
+  public Pet name(String name) {
+    
+    this.name = name;
+    return this;
+  }
+
+   /**
+   * Get name
+   * @return name
+  **/
+  @ApiModelProperty(example = "doggie", required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public String getName() {
+    return name;
+  }
+
+
+  public void setName(String name) {
+    this.name = name;
+  }
+
+
+  public Pet photoUrls(Set<String> photoUrls) {
+    
+    this.photoUrls = photoUrls;
+    return this;
+  }
+
+  public Pet addPhotoUrlsItem(String photoUrlsItem) {
+    this.photoUrls.add(photoUrlsItem);
+    return this;
+  }
+
+   /**
+   * Get photoUrls
+   * @return photoUrls
+  **/
+  @ApiModelProperty(required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_PHOTO_URLS)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public Set<String> getPhotoUrls() {
+    return photoUrls;
+  }
+
+
+  public void setPhotoUrls(Set<String> photoUrls) {
+    this.photoUrls = photoUrls;
+  }
+
+
+  public Pet tags(List<Tag> tags) {
+    
+    this.tags = tags;
+    return this;
+  }
+
+  public Pet addTagsItem(Tag tagsItem) {
+    if (this.tags == null) {
+      this.tags = new ArrayList<Tag>();
+    }
+    this.tags.add(tagsItem);
+    return this;
+  }
+
+   /**
+   * Get tags
+   * @return tags
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_TAGS)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public List<Tag> getTags() {
+    return tags;
+  }
+
+
+  public void setTags(List<Tag> tags) {
+    this.tags = tags;
+  }
+
+
+  public Pet status(StatusEnum status) {
+    
+    this.status = status;
+    return this;
+  }
+
+   /**
+   * pet status in the store
+   * @return status
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "pet status in the store")
+  @JsonProperty(JSON_PROPERTY_STATUS)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public StatusEnum getStatus() {
+    return status;
+  }
+
+
+  public void setStatus(StatusEnum status) {
+    this.status = status;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    Pet pet = (Pet) o;
+    return Objects.equals(this.id, pet.id) &&
+        Objects.equals(this.category, pet.category) &&
+        Objects.equals(this.name, pet.name) &&
+        Objects.equals(this.photoUrls, pet.photoUrls) &&
+        Objects.equals(this.tags, pet.tags) &&
+        Objects.equals(this.status, pet.status);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(id, category, name, photoUrls, tags, status);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class Pet {\n");
+    sb.append("    id: ").append(toIndentedString(id)).append("\n");
+    sb.append("    category: ").append(toIndentedString(category)).append("\n");
+    sb.append("    name: ").append(toIndentedString(name)).append("\n");
+    sb.append("    photoUrls: ").append(toIndentedString(photoUrls)).append("\n");
+    sb.append("    tags: ").append(toIndentedString(tags)).append("\n");
+    sb.append("    status: ").append(toIndentedString(status)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/ReadOnlyFirst.java

@@ -0,0 +1,127 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * ReadOnlyFirst
+ */
+@JsonPropertyOrder({
+  ReadOnlyFirst.JSON_PROPERTY_BAR,
+  ReadOnlyFirst.JSON_PROPERTY_BAZ
+})
+@JsonTypeName("ReadOnlyFirst")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class ReadOnlyFirst {
+  public static final String JSON_PROPERTY_BAR = "bar";
+  private String bar;
+
+  public static final String JSON_PROPERTY_BAZ = "baz";
+  private String baz;
+
+
+   /**
+   * Get bar
+   * @return bar
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_BAR)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getBar() {
+    return bar;
+  }
+
+
+
+
+  public ReadOnlyFirst baz(String baz) {
+    
+    this.baz = baz;
+    return this;
+  }
+
+   /**
+   * Get baz
+   * @return baz
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_BAZ)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getBaz() {
+    return baz;
+  }
+
+
+  public void setBaz(String baz) {
+    this.baz = baz;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    ReadOnlyFirst readOnlyFirst = (ReadOnlyFirst) o;
+    return Objects.equals(this.bar, readOnlyFirst.bar) &&
+        Objects.equals(this.baz, readOnlyFirst.baz);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(bar, baz);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class ReadOnlyFirst {\n");
+    sb.append("    bar: ").append(toIndentedString(bar)).append("\n");
+    sb.append("    baz: ").append(toIndentedString(baz)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/SpecialModelName.java

@@ -0,0 +1,105 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * SpecialModelName
+ */
+@JsonPropertyOrder({
+  SpecialModelName.JSON_PROPERTY_$_SPECIAL_PROPERTY_NAME
+})
+@JsonTypeName("$special[model.name]")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class SpecialModelName {
+  public static final String JSON_PROPERTY_$_SPECIAL_PROPERTY_NAME = "$special[property.name]";
+  private Long $specialPropertyName;
+
+
+  public SpecialModelName $specialPropertyName(Long $specialPropertyName) {
+    
+    this.$specialPropertyName = $specialPropertyName;
+    return this;
+  }
+
+   /**
+   * Get $specialPropertyName
+   * @return $specialPropertyName
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_$_SPECIAL_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Long get$SpecialPropertyName() {
+    return $specialPropertyName;
+  }
+
+
+  public void set$SpecialPropertyName(Long $specialPropertyName) {
+    this.$specialPropertyName = $specialPropertyName;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    SpecialModelName $specialModelName = (SpecialModelName) o;
+    return Objects.equals(this.$specialPropertyName, $specialModelName.$specialPropertyName);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash($specialPropertyName);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class SpecialModelName {\n");
+    sb.append("    $specialPropertyName: ").append(toIndentedString($specialPropertyName)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/Tag.java

@@ -0,0 +1,136 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * Tag
+ */
+@JsonPropertyOrder({
+  Tag.JSON_PROPERTY_ID,
+  Tag.JSON_PROPERTY_NAME
+})
+@JsonTypeName("Tag")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Tag {
+  public static final String JSON_PROPERTY_ID = "id";
+  private Long id;
+
+  public static final String JSON_PROPERTY_NAME = "name";
+  private String name;
+
+
+  public Tag id(Long id) {
+    
+    this.id = id;
+    return this;
+  }
+
+   /**
+   * Get id
+   * @return id
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_ID)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Long getId() {
+    return id;
+  }
+
+
+  public void setId(Long id) {
+    this.id = id;
+  }
+
+
+  public Tag name(String name) {
+    
+    this.name = name;
+    return this;
+  }
+
+   /**
+   * Get name
+   * @return name
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getName() {
+    return name;
+  }
+
+
+  public void setName(String name) {
+    this.name = name;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    Tag tag = (Tag) o;
+    return Objects.equals(this.id, tag.id) &&
+        Objects.equals(this.name, tag.name);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(id, name);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class Tag {\n");
+    sb.append("    id: ").append(toIndentedString(id)).append("\n");
+    sb.append("    name: ").append(toIndentedString(name)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/TypeHolderDefault.java

@@ -0,0 +1,232 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.math.BigDecimal;
+import java.util.ArrayList;
+import java.util.List;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * TypeHolderDefault
+ */
+@JsonPropertyOrder({
+  TypeHolderDefault.JSON_PROPERTY_STRING_ITEM,
+  TypeHolderDefault.JSON_PROPERTY_NUMBER_ITEM,
+  TypeHolderDefault.JSON_PROPERTY_INTEGER_ITEM,
+  TypeHolderDefault.JSON_PROPERTY_BOOL_ITEM,
+  TypeHolderDefault.JSON_PROPERTY_ARRAY_ITEM
+})
+@JsonTypeName("TypeHolderDefault")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class TypeHolderDefault {
+  public static final String JSON_PROPERTY_STRING_ITEM = "string_item";
+  private String stringItem = "what";
+
+  public static final String JSON_PROPERTY_NUMBER_ITEM = "number_item";
+  private BigDecimal numberItem;
+
+  public static final String JSON_PROPERTY_INTEGER_ITEM = "integer_item";
+  private Integer integerItem;
+
+  public static final String JSON_PROPERTY_BOOL_ITEM = "bool_item";
+  private Boolean boolItem = true;
+
+  public static final String JSON_PROPERTY_ARRAY_ITEM = "array_item";
+  private List<Integer> arrayItem = new ArrayList<Integer>();
+
+
+  public TypeHolderDefault stringItem(String stringItem) {
+    
+    this.stringItem = stringItem;
+    return this;
+  }
+
+   /**
+   * Get stringItem
+   * @return stringItem
+  **/
+  @ApiModelProperty(required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_STRING_ITEM)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public String getStringItem() {
+    return stringItem;
+  }
+
+
+  public void setStringItem(String stringItem) {
+    this.stringItem = stringItem;
+  }
+
+
+  public TypeHolderDefault numberItem(BigDecimal numberItem) {
+    
+    this.numberItem = numberItem;
+    return this;
+  }
+
+   /**
+   * Get numberItem
+   * @return numberItem
+  **/
+  @ApiModelProperty(required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_NUMBER_ITEM)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public BigDecimal getNumberItem() {
+    return numberItem;
+  }
+
+
+  public void setNumberItem(BigDecimal numberItem) {
+    this.numberItem = numberItem;
+  }
+
+
+  public TypeHolderDefault integerItem(Integer integerItem) {
+    
+    this.integerItem = integerItem;
+    return this;
+  }
+
+   /**
+   * Get integerItem
+   * @return integerItem
+  **/
+  @ApiModelProperty(required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_INTEGER_ITEM)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public Integer getIntegerItem() {
+    return integerItem;
+  }
+
+
+  public void setIntegerItem(Integer integerItem) {
+    this.integerItem = integerItem;
+  }
+
+
+  public TypeHolderDefault boolItem(Boolean boolItem) {
+    
+    this.boolItem = boolItem;
+    return this;
+  }
+
+   /**
+   * Get boolItem
+   * @return boolItem
+  **/
+  @ApiModelProperty(required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_BOOL_ITEM)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public Boolean isBoolItem() {
+    return boolItem;
+  }
+
+
+  public void setBoolItem(Boolean boolItem) {
+    this.boolItem = boolItem;
+  }
+
+
+  public TypeHolderDefault arrayItem(List<Integer> arrayItem) {
+    
+    this.arrayItem = arrayItem;
+    return this;
+  }
+
+  public TypeHolderDefault addArrayItemItem(Integer arrayItemItem) {
+    this.arrayItem.add(arrayItemItem);
+    return this;
+  }
+
+   /**
+   * Get arrayItem
+   * @return arrayItem
+  **/
+  @ApiModelProperty(required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_ARRAY_ITEM)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public List<Integer> getArrayItem() {
+    return arrayItem;
+  }
+
+
+  public void setArrayItem(List<Integer> arrayItem) {
+    this.arrayItem = arrayItem;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    TypeHolderDefault typeHolderDefault = (TypeHolderDefault) o;
+    return Objects.equals(this.stringItem, typeHolderDefault.stringItem) &&
+        Objects.equals(this.numberItem, typeHolderDefault.numberItem) &&
+        Objects.equals(this.integerItem, typeHolderDefault.integerItem) &&
+        Objects.equals(this.boolItem, typeHolderDefault.boolItem) &&
+        Objects.equals(this.arrayItem, typeHolderDefault.arrayItem);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(stringItem, numberItem, integerItem, boolItem, arrayItem);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class TypeHolderDefault {\n");
+    sb.append("    stringItem: ").append(toIndentedString(stringItem)).append("\n");
+    sb.append("    numberItem: ").append(toIndentedString(numberItem)).append("\n");
+    sb.append("    integerItem: ").append(toIndentedString(integerItem)).append("\n");
+    sb.append("    boolItem: ").append(toIndentedString(boolItem)).append("\n");
+    sb.append("    arrayItem: ").append(toIndentedString(arrayItem)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/TypeHolderExample.java

@@ -0,0 +1,262 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.math.BigDecimal;
+import java.util.ArrayList;
+import java.util.List;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * TypeHolderExample
+ */
+@JsonPropertyOrder({
+  TypeHolderExample.JSON_PROPERTY_STRING_ITEM,
+  TypeHolderExample.JSON_PROPERTY_NUMBER_ITEM,
+  TypeHolderExample.JSON_PROPERTY_FLOAT_ITEM,
+  TypeHolderExample.JSON_PROPERTY_INTEGER_ITEM,
+  TypeHolderExample.JSON_PROPERTY_BOOL_ITEM,
+  TypeHolderExample.JSON_PROPERTY_ARRAY_ITEM
+})
+@JsonTypeName("TypeHolderExample")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class TypeHolderExample {
+  public static final String JSON_PROPERTY_STRING_ITEM = "string_item";
+  private String stringItem;
+
+  public static final String JSON_PROPERTY_NUMBER_ITEM = "number_item";
+  private BigDecimal numberItem;
+
+  public static final String JSON_PROPERTY_FLOAT_ITEM = "float_item";
+  private Float floatItem;
+
+  public static final String JSON_PROPERTY_INTEGER_ITEM = "integer_item";
+  private Integer integerItem;
+
+  public static final String JSON_PROPERTY_BOOL_ITEM = "bool_item";
+  private Boolean boolItem;
+
+  public static final String JSON_PROPERTY_ARRAY_ITEM = "array_item";
+  private List<Integer> arrayItem = new ArrayList<Integer>();
+
+
+  public TypeHolderExample stringItem(String stringItem) {
+    
+    this.stringItem = stringItem;
+    return this;
+  }
+
+   /**
+   * Get stringItem
+   * @return stringItem
+  **/
+  @ApiModelProperty(example = "what", required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_STRING_ITEM)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public String getStringItem() {
+    return stringItem;
+  }
+
+
+  public void setStringItem(String stringItem) {
+    this.stringItem = stringItem;
+  }
+
+
+  public TypeHolderExample numberItem(BigDecimal numberItem) {
+    
+    this.numberItem = numberItem;
+    return this;
+  }
+
+   /**
+   * Get numberItem
+   * @return numberItem
+  **/
+  @ApiModelProperty(example = "1.234", required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_NUMBER_ITEM)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public BigDecimal getNumberItem() {
+    return numberItem;
+  }
+
+
+  public void setNumberItem(BigDecimal numberItem) {
+    this.numberItem = numberItem;
+  }
+
+
+  public TypeHolderExample floatItem(Float floatItem) {
+    
+    this.floatItem = floatItem;
+    return this;
+  }
+
+   /**
+   * Get floatItem
+   * @return floatItem
+  **/
+  @ApiModelProperty(example = "1.234", required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_FLOAT_ITEM)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public Float getFloatItem() {
+    return floatItem;
+  }
+
+
+  public void setFloatItem(Float floatItem) {
+    this.floatItem = floatItem;
+  }
+
+
+  public TypeHolderExample integerItem(Integer integerItem) {
+    
+    this.integerItem = integerItem;
+    return this;
+  }
+
+   /**
+   * Get integerItem
+   * @return integerItem
+  **/
+  @ApiModelProperty(example = "-2", required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_INTEGER_ITEM)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public Integer getIntegerItem() {
+    return integerItem;
+  }
+
+
+  public void setIntegerItem(Integer integerItem) {
+    this.integerItem = integerItem;
+  }
+
+
+  public TypeHolderExample boolItem(Boolean boolItem) {
+    
+    this.boolItem = boolItem;
+    return this;
+  }
+
+   /**
+   * Get boolItem
+   * @return boolItem
+  **/
+  @ApiModelProperty(example = "true", required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_BOOL_ITEM)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public Boolean isBoolItem() {
+    return boolItem;
+  }
+
+
+  public void setBoolItem(Boolean boolItem) {
+    this.boolItem = boolItem;
+  }
+
+
+  public TypeHolderExample arrayItem(List<Integer> arrayItem) {
+    
+    this.arrayItem = arrayItem;
+    return this;
+  }
+
+  public TypeHolderExample addArrayItemItem(Integer arrayItemItem) {
+    this.arrayItem.add(arrayItemItem);
+    return this;
+  }
+
+   /**
+   * Get arrayItem
+   * @return arrayItem
+  **/
+  @ApiModelProperty(example = "[0, 1, 2, 3]", required = true, value = "")
+  @JsonProperty(JSON_PROPERTY_ARRAY_ITEM)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public List<Integer> getArrayItem() {
+    return arrayItem;
+  }
+
+
+  public void setArrayItem(List<Integer> arrayItem) {
+    this.arrayItem = arrayItem;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    TypeHolderExample typeHolderExample = (TypeHolderExample) o;
+    return Objects.equals(this.stringItem, typeHolderExample.stringItem) &&
+        Objects.equals(this.numberItem, typeHolderExample.numberItem) &&
+        Objects.equals(this.floatItem, typeHolderExample.floatItem) &&
+        Objects.equals(this.integerItem, typeHolderExample.integerItem) &&
+        Objects.equals(this.boolItem, typeHolderExample.boolItem) &&
+        Objects.equals(this.arrayItem, typeHolderExample.arrayItem);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(stringItem, numberItem, floatItem, integerItem, boolItem, arrayItem);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class TypeHolderExample {\n");
+    sb.append("    stringItem: ").append(toIndentedString(stringItem)).append("\n");
+    sb.append("    numberItem: ").append(toIndentedString(numberItem)).append("\n");
+    sb.append("    floatItem: ").append(toIndentedString(floatItem)).append("\n");
+    sb.append("    integerItem: ").append(toIndentedString(integerItem)).append("\n");
+    sb.append("    boolItem: ").append(toIndentedString(boolItem)).append("\n");
+    sb.append("    arrayItem: ").append(toIndentedString(arrayItem)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/model/User.java

@@ -0,0 +1,322 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+/**
+ * User
+ */
+@JsonPropertyOrder({
+  User.JSON_PROPERTY_ID,
+  User.JSON_PROPERTY_USERNAME,
+  User.JSON_PROPERTY_FIRST_NAME,
+  User.JSON_PROPERTY_LAST_NAME,
+  User.JSON_PROPERTY_EMAIL,
+  User.JSON_PROPERTY_PASSWORD,
+  User.JSON_PROPERTY_PHONE,
+  User.JSON_PROPERTY_USER_STATUS
+})
+@JsonTypeName("User")
+@javax.annotation.concurrent.Immutable
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class User {
+  public static final String JSON_PROPERTY_ID = "id";
+  private Long id;
+
+  public static final String JSON_PROPERTY_USERNAME = "username";
+  private String username;
+
+  public static final String JSON_PROPERTY_FIRST_NAME = "firstName";
+  private String firstName;
+
+  public static final String JSON_PROPERTY_LAST_NAME = "lastName";
+  private String lastName;
+
+  public static final String JSON_PROPERTY_EMAIL = "email";
+  private String email;
+
+  public static final String JSON_PROPERTY_PASSWORD = "password";
+  private String password;
+
+  public static final String JSON_PROPERTY_PHONE = "phone";
+  private String phone;
+
+  public static final String JSON_PROPERTY_USER_STATUS = "userStatus";
+  private Integer userStatus;
+
+
+  public User id(Long id) {
+    
+    this.id = id;
+    return this;
+  }
+
+   /**
+   * Get id
+   * @return id
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_ID)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Long getId() {
+    return id;
+  }
+
+
+  public void setId(Long id) {
+    this.id = id;
+  }
+
+
+  public User username(String username) {
+    
+    this.username = username;
+    return this;
+  }
+
+   /**
+   * Get username
+   * @return username
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_USERNAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getUsername() {
+    return username;
+  }
+
+
+  public void setUsername(String username) {
+    this.username = username;
+  }
+
+
+  public User firstName(String firstName) {
+    
+    this.firstName = firstName;
+    return this;
+  }
+
+   /**
+   * Get firstName
+   * @return firstName
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_FIRST_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getFirstName() {
+    return firstName;
+  }
+
+
+  public void setFirstName(String firstName) {
+    this.firstName = firstName;
+  }
+
+
+  public User lastName(String lastName) {
+    
+    this.lastName = lastName;
+    return this;
+  }
+
+   /**
+   * Get lastName
+   * @return lastName
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_LAST_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getLastName() {
+    return lastName;
+  }
+
+
+  public void setLastName(String lastName) {
+    this.lastName = lastName;
+  }
+
+
+  public User email(String email) {
+    
+    this.email = email;
+    return this;
+  }
+
+   /**
+   * Get email
+   * @return email
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_EMAIL)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getEmail() {
+    return email;
+  }
+
+
+  public void setEmail(String email) {
+    this.email = email;
+  }
+
+
+  public User password(String password) {
+    
+    this.password = password;
+    return this;
+  }
+
+   /**
+   * Get password
+   * @return password
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_PASSWORD)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getPassword() {
+    return password;
+  }
+
+
+  public void setPassword(String password) {
+    this.password = password;
+  }
+
+
+  public User phone(String phone) {
+    
+    this.phone = phone;
+    return this;
+  }
+
+   /**
+   * Get phone
+   * @return phone
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "")
+  @JsonProperty(JSON_PROPERTY_PHONE)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getPhone() {
+    return phone;
+  }
+
+
+  public void setPhone(String phone) {
+    this.phone = phone;
+  }
+
+
+  public User userStatus(Integer userStatus) {
+    
+    this.userStatus = userStatus;
+    return this;
+  }
+
+   /**
+   * User Status
+   * @return userStatus
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "User Status")
+  @JsonProperty(JSON_PROPERTY_USER_STATUS)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Integer getUserStatus() {
+    return userStatus;
+  }
+
+
+  public void setUserStatus(Integer userStatus) {
+    this.userStatus = userStatus;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    User user = (User) o;
+    return Objects.equals(this.id, user.id) &&
+        Objects.equals(this.username, user.username) &&
+        Objects.equals(this.firstName, user.firstName) &&
+        Objects.equals(this.lastName, user.lastName) &&
+        Objects.equals(this.email, user.email) &&
+        Objects.equals(this.password, user.password) &&
+        Objects.equals(this.phone, user.phone) &&
+        Objects.equals(this.userStatus, user.userStatus);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(id, username, firstName, lastName, email, password, phone, userStatus);
+  }
+
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class User {\n");
+    sb.append("    id: ").append(toIndentedString(id)).append("\n");
+    sb.append("    username: ").append(toIndentedString(username)).append("\n");
+    sb.append("    firstName: ").append(toIndentedString(firstName)).append("\n");
+    sb.append("    lastName: ").append(toIndentedString(lastName)).append("\n");
+    sb.append("    email: ").append(toIndentedString(email)).append("\n");
+    sb.append("    password: ").append(toIndentedString(password)).append("\n");
+    sb.append("    phone: ").append(toIndentedString(phone)).append("\n");
+    sb.append("    userStatus: ").append(toIndentedString(userStatus)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/api/AnotherFakeApiTest.java

@@ -0,0 +1,40 @@
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.model.Client;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * API tests for AnotherFakeApi
+ */
+public class AnotherFakeApiTest {
+
+    private AnotherFakeApi api;
+
+    @Before
+    public void setup() {
+        api = new ApiClient().buildClient(AnotherFakeApi.class);
+    }
+
+    
+    /**
+     * To test special tags
+     *
+     * To test special tags and operation ID starting with number
+     */
+    @Test
+    public void call123testSpecialTagsTest() {
+        Client body = null;
+        // Client response = api.call123testSpecialTags(body);
+
+        // TODO: test validations
+    }
+
+    
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/api/FakeApiTest.java

@@ -0,0 +1,342 @@
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiClient;
+import java.math.BigDecimal;
+import org.openapitools.client.model.Client;
+import java.io.File;
+import org.openapitools.client.model.FileSchemaTestClass;
+import org.threeten.bp.LocalDate;
+import org.threeten.bp.OffsetDateTime;
+import org.openapitools.client.model.OuterComposite;
+import org.openapitools.client.model.User;
+import org.openapitools.client.model.XmlItem;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * API tests for FakeApi
+ */
+public class FakeApiTest {
+
+    private FakeApi api;
+
+    @Before
+    public void setup() {
+        api = new ApiClient().buildClient(FakeApi.class);
+    }
+
+    
+    /**
+     * creates an XmlItem
+     *
+     * this route creates an XmlItem
+     */
+    @Test
+    public void createXmlItemTest() {
+        XmlItem xmlItem = null;
+        // api.createXmlItem(xmlItem);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * 
+     *
+     * Test serialization of outer boolean types
+     */
+    @Test
+    public void fakeOuterBooleanSerializeTest() {
+        Boolean body = null;
+        // Boolean response = api.fakeOuterBooleanSerialize(body);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * 
+     *
+     * Test serialization of object with outer number type
+     */
+    @Test
+    public void fakeOuterCompositeSerializeTest() {
+        OuterComposite body = null;
+        // OuterComposite response = api.fakeOuterCompositeSerialize(body);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * 
+     *
+     * Test serialization of outer number types
+     */
+    @Test
+    public void fakeOuterNumberSerializeTest() {
+        BigDecimal body = null;
+        // BigDecimal response = api.fakeOuterNumberSerialize(body);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * 
+     *
+     * Test serialization of outer string types
+     */
+    @Test
+    public void fakeOuterStringSerializeTest() {
+        String body = null;
+        // String response = api.fakeOuterStringSerialize(body);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * 
+     *
+     * For this test, the body for this request much reference a schema named `File`.
+     */
+    @Test
+    public void testBodyWithFileSchemaTest() {
+        FileSchemaTestClass body = null;
+        // api.testBodyWithFileSchema(body);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * 
+     *
+     * 
+     */
+    @Test
+    public void testBodyWithQueryParamsTest() {
+        String query = null;
+        User body = null;
+        // api.testBodyWithQueryParams(query, body);
+
+        // TODO: test validations
+    }
+
+    /**
+     * 
+     *
+     * 
+     *
+     * This tests the overload of the method that uses a Map for query parameters instead of
+     * listing them out individually.
+     */
+    @Test
+    public void testBodyWithQueryParamsTestQueryMap() {
+        User body = null;
+        FakeApi.TestBodyWithQueryParamsQueryParams queryParams = new FakeApi.TestBodyWithQueryParamsQueryParams()
+            .query(null);
+        // api.testBodyWithQueryParams(body, queryParams);
+
+    // TODO: test validations
+    }
+    
+    /**
+     * To test \"client\" model
+     *
+     * To test \"client\" model
+     */
+    @Test
+    public void testClientModelTest() {
+        Client body = null;
+        // Client response = api.testClientModel(body);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * Fake endpoint for testing various parameters  假端點  偽のエンドポイント  가짜 엔드 포인트
+     *
+     * Fake endpoint for testing various parameters  假端點  偽のエンドポイント  가짜 엔드 포인트
+     */
+    @Test
+    public void testEndpointParametersTest() {
+        BigDecimal number = null;
+        Double _double = null;
+        String patternWithoutDelimiter = null;
+        byte[] _byte = null;
+        Integer integer = null;
+        Integer int32 = null;
+        Long int64 = null;
+        Float _float = null;
+        String string = null;
+        File binary = null;
+        LocalDate date = null;
+        OffsetDateTime dateTime = null;
+        String password = null;
+        String paramCallback = null;
+        // api.testEndpointParameters(number, _double, patternWithoutDelimiter, _byte, integer, int32, int64, _float, string, binary, date, dateTime, password, paramCallback);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * To test enum parameters
+     *
+     * To test enum parameters
+     */
+    @Test
+    public void testEnumParametersTest() {
+        List<String> enumHeaderStringArray = null;
+        String enumHeaderString = null;
+        List<String> enumQueryStringArray = null;
+        String enumQueryString = null;
+        Integer enumQueryInteger = null;
+        Double enumQueryDouble = null;
+        List<String> enumFormStringArray = null;
+        String enumFormString = null;
+        // api.testEnumParameters(enumHeaderStringArray, enumHeaderString, enumQueryStringArray, enumQueryString, enumQueryInteger, enumQueryDouble, enumFormStringArray, enumFormString);
+
+        // TODO: test validations
+    }
+
+    /**
+     * To test enum parameters
+     *
+     * To test enum parameters
+     *
+     * This tests the overload of the method that uses a Map for query parameters instead of
+     * listing them out individually.
+     */
+    @Test
+    public void testEnumParametersTestQueryMap() {
+        List<String> enumHeaderStringArray = null;
+        String enumHeaderString = null;
+        List<String> enumFormStringArray = null;
+        String enumFormString = null;
+        FakeApi.TestEnumParametersQueryParams queryParams = new FakeApi.TestEnumParametersQueryParams()
+            .enumQueryStringArray(null)
+            .enumQueryString(null)
+            .enumQueryInteger(null)
+            .enumQueryDouble(null);
+        // api.testEnumParameters(enumHeaderStringArray, enumHeaderString, enumFormStringArray, enumFormString, queryParams);
+
+    // TODO: test validations
+    }
+    
+    /**
+     * Fake endpoint to test group parameters (optional)
+     *
+     * Fake endpoint to test group parameters (optional)
+     */
+    @Test
+    public void testGroupParametersTest() {
+        Integer requiredStringGroup = null;
+        Boolean requiredBooleanGroup = null;
+        Long requiredInt64Group = null;
+        Integer stringGroup = null;
+        Boolean booleanGroup = null;
+        Long int64Group = null;
+        // api.testGroupParameters(requiredStringGroup, requiredBooleanGroup, requiredInt64Group, stringGroup, booleanGroup, int64Group);
+
+        // TODO: test validations
+    }
+
+    /**
+     * Fake endpoint to test group parameters (optional)
+     *
+     * Fake endpoint to test group parameters (optional)
+     *
+     * This tests the overload of the method that uses a Map for query parameters instead of
+     * listing them out individually.
+     */
+    @Test
+    public void testGroupParametersTestQueryMap() {
+        Boolean requiredBooleanGroup = null;
+        Boolean booleanGroup = null;
+        FakeApi.TestGroupParametersQueryParams queryParams = new FakeApi.TestGroupParametersQueryParams()
+            .requiredStringGroup(null)
+            .requiredInt64Group(null)
+            .stringGroup(null)
+            .int64Group(null);
+        // api.testGroupParameters(requiredBooleanGroup, booleanGroup, queryParams);
+
+    // TODO: test validations
+    }
+    
+    /**
+     * test inline additionalProperties
+     *
+     * 
+     */
+    @Test
+    public void testInlineAdditionalPropertiesTest() {
+        Map<String, String> param = null;
+        // api.testInlineAdditionalProperties(param);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * test json serialization of form data
+     *
+     * 
+     */
+    @Test
+    public void testJsonFormDataTest() {
+        String param = null;
+        String param2 = null;
+        // api.testJsonFormData(param, param2);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * 
+     *
+     * To test the collection format in query parameters
+     */
+    @Test
+    public void testQueryParameterCollectionFormatTest() {
+        List<String> pipe = null;
+        List<String> ioutil = null;
+        List<String> http = null;
+        List<String> url = null;
+        List<String> context = null;
+        // api.testQueryParameterCollectionFormat(pipe, ioutil, http, url, context);
+
+        // TODO: test validations
+    }
+
+    /**
+     * 
+     *
+     * To test the collection format in query parameters
+     *
+     * This tests the overload of the method that uses a Map for query parameters instead of
+     * listing them out individually.
+     */
+    @Test
+    public void testQueryParameterCollectionFormatTestQueryMap() {
+        FakeApi.TestQueryParameterCollectionFormatQueryParams queryParams = new FakeApi.TestQueryParameterCollectionFormatQueryParams()
+            .pipe(null)
+            .ioutil(null)
+            .http(null)
+            .url(null)
+            .context(null);
+        // api.testQueryParameterCollectionFormat(queryParams);
+
+    // TODO: test validations
+    }
+    
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/api/FakeClassnameTags123ApiTest.java

@@ -0,0 +1,40 @@
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.model.Client;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * API tests for FakeClassnameTags123Api
+ */
+public class FakeClassnameTags123ApiTest {
+
+    private FakeClassnameTags123Api api;
+
+    @Before
+    public void setup() {
+        api = new ApiClient().buildClient(FakeClassnameTags123Api.class);
+    }
+
+    
+    /**
+     * To test class name in snake case
+     *
+     * To test class name in snake case
+     */
+    @Test
+    public void testClassnameTest() {
+        Client body = null;
+        // Client response = api.testClassname(body);
+
+        // TODO: test validations
+    }
+
+    
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/api/PetApiTest.java

@@ -0,0 +1,194 @@
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiClient;
+import java.io.File;
+import org.openapitools.client.model.ModelApiResponse;
+import org.openapitools.client.model.Pet;
+import java.util.Set;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * API tests for PetApi
+ */
+public class PetApiTest {
+
+    private PetApi api;
+
+    @Before
+    public void setup() {
+        api = new ApiClient().buildClient(PetApi.class);
+    }
+
+    
+    /**
+     * Add a new pet to the store
+     *
+     * 
+     */
+    @Test
+    public void addPetTest() {
+        Pet body = null;
+        // api.addPet(body);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * Deletes a pet
+     *
+     * 
+     */
+    @Test
+    public void deletePetTest() {
+        Long petId = null;
+        String apiKey = null;
+        // api.deletePet(petId, apiKey);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * Finds Pets by status
+     *
+     * Multiple status values can be provided with comma separated strings
+     */
+    @Test
+    public void findPetsByStatusTest() {
+        List<String> status = null;
+        // List<Pet> response = api.findPetsByStatus(status);
+
+        // TODO: test validations
+    }
+
+    /**
+     * Finds Pets by status
+     *
+     * Multiple status values can be provided with comma separated strings
+     *
+     * This tests the overload of the method that uses a Map for query parameters instead of
+     * listing them out individually.
+     */
+    @Test
+    public void findPetsByStatusTestQueryMap() {
+        PetApi.FindPetsByStatusQueryParams queryParams = new PetApi.FindPetsByStatusQueryParams()
+            .status(null);
+        // List<Pet> response = api.findPetsByStatus(queryParams);
+
+    // TODO: test validations
+    }
+    
+    /**
+     * Finds Pets by tags
+     *
+     * Multiple tags can be provided with comma separated strings. Use tag1, tag2, tag3 for testing.
+     */
+    @Test
+    public void findPetsByTagsTest() {
+        Set<String> tags = null;
+        // Set<Pet> response = api.findPetsByTags(tags);
+
+        // TODO: test validations
+    }
+
+    /**
+     * Finds Pets by tags
+     *
+     * Multiple tags can be provided with comma separated strings. Use tag1, tag2, tag3 for testing.
+     *
+     * This tests the overload of the method that uses a Map for query parameters instead of
+     * listing them out individually.
+     */
+    @Test
+    public void findPetsByTagsTestQueryMap() {
+        PetApi.FindPetsByTagsQueryParams queryParams = new PetApi.FindPetsByTagsQueryParams()
+            .tags(null);
+        // Set<Pet> response = api.findPetsByTags(queryParams);
+
+    // TODO: test validations
+    }
+    
+    /**
+     * Find pet by ID
+     *
+     * Returns a single pet
+     */
+    @Test
+    public void getPetByIdTest() {
+        Long petId = null;
+        // Pet response = api.getPetById(petId);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * Update an existing pet
+     *
+     * 
+     */
+    @Test
+    public void updatePetTest() {
+        Pet body = null;
+        // api.updatePet(body);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * Updates a pet in the store with form data
+     *
+     * 
+     */
+    @Test
+    public void updatePetWithFormTest() {
+        Long petId = null;
+        String name = null;
+        String status = null;
+        // api.updatePetWithForm(petId, name, status);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * uploads an image
+     *
+     * 
+     */
+    @Test
+    public void uploadFileTest() {
+        Long petId = null;
+        String additionalMetadata = null;
+        File file = null;
+        // ModelApiResponse response = api.uploadFile(petId, additionalMetadata, file);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * uploads an image (required)
+     *
+     * 
+     */
+    @Test
+    public void uploadFileWithRequiredFileTest() {
+        Long petId = null;
+        File requiredFile = null;
+        String additionalMetadata = null;
+        // ModelApiResponse response = api.uploadFileWithRequiredFile(petId, requiredFile, additionalMetadata);
+
+        // TODO: test validations
+    }
+
+    
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/api/StoreApiTest.java

@@ -0,0 +1,81 @@
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.model.Order;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * API tests for StoreApi
+ */
+public class StoreApiTest {
+
+    private StoreApi api;
+
+    @Before
+    public void setup() {
+        api = new ApiClient().buildClient(StoreApi.class);
+    }
+
+    
+    /**
+     * Delete purchase order by ID
+     *
+     * For valid response try integer IDs with value < 1000. Anything above 1000 or nonintegers will generate API errors
+     */
+    @Test
+    public void deleteOrderTest() {
+        String orderId = null;
+        // api.deleteOrder(orderId);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * Returns pet inventories by status
+     *
+     * Returns a map of status codes to quantities
+     */
+    @Test
+    public void getInventoryTest() {
+        // Map<String, Integer> response = api.getInventory();
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * Find purchase order by ID
+     *
+     * For valid response try integer IDs with value &lt;&#x3D; 5 or &gt; 10. Other values will generated exceptions
+     */
+    @Test
+    public void getOrderByIdTest() {
+        Long orderId = null;
+        // Order response = api.getOrderById(orderId);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * Place an order for a pet
+     *
+     * 
+     */
+    @Test
+    public void placeOrderTest() {
+        Order body = null;
+        // Order response = api.placeOrder(body);
+
+        // TODO: test validations
+    }
+
+    
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/api/UserApiTest.java

@@ -0,0 +1,156 @@
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.model.User;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * API tests for UserApi
+ */
+public class UserApiTest {
+
+    private UserApi api;
+
+    @Before
+    public void setup() {
+        api = new ApiClient().buildClient(UserApi.class);
+    }
+
+    
+    /**
+     * Create user
+     *
+     * This can only be done by the logged in user.
+     */
+    @Test
+    public void createUserTest() {
+        User body = null;
+        // api.createUser(body);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * Creates list of users with given input array
+     *
+     * 
+     */
+    @Test
+    public void createUsersWithArrayInputTest() {
+        List<User> body = null;
+        // api.createUsersWithArrayInput(body);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * Creates list of users with given input array
+     *
+     * 
+     */
+    @Test
+    public void createUsersWithListInputTest() {
+        List<User> body = null;
+        // api.createUsersWithListInput(body);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * Delete user
+     *
+     * This can only be done by the logged in user.
+     */
+    @Test
+    public void deleteUserTest() {
+        String username = null;
+        // api.deleteUser(username);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * Get user by user name
+     *
+     * 
+     */
+    @Test
+    public void getUserByNameTest() {
+        String username = null;
+        // User response = api.getUserByName(username);
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * Logs user into the system
+     *
+     * 
+     */
+    @Test
+    public void loginUserTest() {
+        String username = null;
+        String password = null;
+        // String response = api.loginUser(username, password);
+
+        // TODO: test validations
+    }
+
+    /**
+     * Logs user into the system
+     *
+     * 
+     *
+     * This tests the overload of the method that uses a Map for query parameters instead of
+     * listing them out individually.
+     */
+    @Test
+    public void loginUserTestQueryMap() {
+        UserApi.LoginUserQueryParams queryParams = new UserApi.LoginUserQueryParams()
+            .username(null)
+            .password(null);
+        // String response = api.loginUser(queryParams);
+
+    // TODO: test validations
+    }
+    
+    /**
+     * Logs out current logged in user session
+     *
+     * 
+     */
+    @Test
+    public void logoutUserTest() {
+        // api.logoutUser();
+
+        // TODO: test validations
+    }
+
+    
+    /**
+     * Updated user
+     *
+     * This can only be done by the logged in user.
+     */
+    @Test
+    public void updateUserTest() {
+        String username = null;
+        User body = null;
+        // api.updateUser(username, body);
+
+        // TODO: test validations
+    }
+
+    
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/AdditionalPropertiesAnyTypeTest.java

@@ -0,0 +1,52 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.HashMap;
+import java.util.Map;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for AdditionalPropertiesAnyType
+ */
+public class AdditionalPropertiesAnyTypeTest {
+    private final AdditionalPropertiesAnyType model = new AdditionalPropertiesAnyType();
+
+    /**
+     * Model tests for AdditionalPropertiesAnyType
+     */
+    @Test
+    public void testAdditionalPropertiesAnyType() {
+        // TODO: test AdditionalPropertiesAnyType
+    }
+
+    /**
+     * Test the property 'name'
+     */
+    @Test
+    public void nameTest() {
+        // TODO: test name
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/AdditionalPropertiesArrayTest.java

@@ -0,0 +1,53 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for AdditionalPropertiesArray
+ */
+public class AdditionalPropertiesArrayTest {
+    private final AdditionalPropertiesArray model = new AdditionalPropertiesArray();
+
+    /**
+     * Model tests for AdditionalPropertiesArray
+     */
+    @Test
+    public void testAdditionalPropertiesArray() {
+        // TODO: test AdditionalPropertiesArray
+    }
+
+    /**
+     * Test the property 'name'
+     */
+    @Test
+    public void nameTest() {
+        // TODO: test name
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/AdditionalPropertiesBooleanTest.java

@@ -0,0 +1,52 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.HashMap;
+import java.util.Map;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for AdditionalPropertiesBoolean
+ */
+public class AdditionalPropertiesBooleanTest {
+    private final AdditionalPropertiesBoolean model = new AdditionalPropertiesBoolean();
+
+    /**
+     * Model tests for AdditionalPropertiesBoolean
+     */
+    @Test
+    public void testAdditionalPropertiesBoolean() {
+        // TODO: test AdditionalPropertiesBoolean
+    }
+
+    /**
+     * Test the property 'name'
+     */
+    @Test
+    public void nameTest() {
+        // TODO: test name
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/AdditionalPropertiesClassTest.java

@@ -0,0 +1,134 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.math.BigDecimal;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for AdditionalPropertiesClass
+ */
+public class AdditionalPropertiesClassTest {
+    private final AdditionalPropertiesClass model = new AdditionalPropertiesClass();
+
+    /**
+     * Model tests for AdditionalPropertiesClass
+     */
+    @Test
+    public void testAdditionalPropertiesClass() {
+        // TODO: test AdditionalPropertiesClass
+    }
+
+    /**
+     * Test the property 'mapString'
+     */
+    @Test
+    public void mapStringTest() {
+        // TODO: test mapString
+    }
+
+    /**
+     * Test the property 'mapNumber'
+     */
+    @Test
+    public void mapNumberTest() {
+        // TODO: test mapNumber
+    }
+
+    /**
+     * Test the property 'mapInteger'
+     */
+    @Test
+    public void mapIntegerTest() {
+        // TODO: test mapInteger
+    }
+
+    /**
+     * Test the property 'mapBoolean'
+     */
+    @Test
+    public void mapBooleanTest() {
+        // TODO: test mapBoolean
+    }
+
+    /**
+     * Test the property 'mapArrayInteger'
+     */
+    @Test
+    public void mapArrayIntegerTest() {
+        // TODO: test mapArrayInteger
+    }
+
+    /**
+     * Test the property 'mapArrayAnytype'
+     */
+    @Test
+    public void mapArrayAnytypeTest() {
+        // TODO: test mapArrayAnytype
+    }
+
+    /**
+     * Test the property 'mapMapString'
+     */
+    @Test
+    public void mapMapStringTest() {
+        // TODO: test mapMapString
+    }
+
+    /**
+     * Test the property 'mapMapAnytype'
+     */
+    @Test
+    public void mapMapAnytypeTest() {
+        // TODO: test mapMapAnytype
+    }
+
+    /**
+     * Test the property 'anytype1'
+     */
+    @Test
+    public void anytype1Test() {
+        // TODO: test anytype1
+    }
+
+    /**
+     * Test the property 'anytype2'
+     */
+    @Test
+    public void anytype2Test() {
+        // TODO: test anytype2
+    }
+
+    /**
+     * Test the property 'anytype3'
+     */
+    @Test
+    public void anytype3Test() {
+        // TODO: test anytype3
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/AdditionalPropertiesIntegerTest.java

@@ -0,0 +1,52 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.HashMap;
+import java.util.Map;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for AdditionalPropertiesInteger
+ */
+public class AdditionalPropertiesIntegerTest {
+    private final AdditionalPropertiesInteger model = new AdditionalPropertiesInteger();
+
+    /**
+     * Model tests for AdditionalPropertiesInteger
+     */
+    @Test
+    public void testAdditionalPropertiesInteger() {
+        // TODO: test AdditionalPropertiesInteger
+    }
+
+    /**
+     * Test the property 'name'
+     */
+    @Test
+    public void nameTest() {
+        // TODO: test name
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/AdditionalPropertiesNumberTest.java

@@ -0,0 +1,53 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.math.BigDecimal;
+import java.util.HashMap;
+import java.util.Map;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for AdditionalPropertiesNumber
+ */
+public class AdditionalPropertiesNumberTest {
+    private final AdditionalPropertiesNumber model = new AdditionalPropertiesNumber();
+
+    /**
+     * Model tests for AdditionalPropertiesNumber
+     */
+    @Test
+    public void testAdditionalPropertiesNumber() {
+        // TODO: test AdditionalPropertiesNumber
+    }
+
+    /**
+     * Test the property 'name'
+     */
+    @Test
+    public void nameTest() {
+        // TODO: test name
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/AdditionalPropertiesObjectTest.java

@@ -0,0 +1,52 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.HashMap;
+import java.util.Map;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for AdditionalPropertiesObject
+ */
+public class AdditionalPropertiesObjectTest {
+    private final AdditionalPropertiesObject model = new AdditionalPropertiesObject();
+
+    /**
+     * Model tests for AdditionalPropertiesObject
+     */
+    @Test
+    public void testAdditionalPropertiesObject() {
+        // TODO: test AdditionalPropertiesObject
+    }
+
+    /**
+     * Test the property 'name'
+     */
+    @Test
+    public void nameTest() {
+        // TODO: test name
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/AdditionalPropertiesStringTest.java

@@ -0,0 +1,52 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.HashMap;
+import java.util.Map;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for AdditionalPropertiesString
+ */
+public class AdditionalPropertiesStringTest {
+    private final AdditionalPropertiesString model = new AdditionalPropertiesString();
+
+    /**
+     * Model tests for AdditionalPropertiesString
+     */
+    @Test
+    public void testAdditionalPropertiesString() {
+        // TODO: test AdditionalPropertiesString
+    }
+
+    /**
+     * Test the property 'name'
+     */
+    @Test
+    public void nameTest() {
+        // TODO: test name
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/AnimalTest.java

@@ -0,0 +1,63 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.openapitools.client.model.BigCat;
+import org.openapitools.client.model.Cat;
+import org.openapitools.client.model.Dog;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for Animal
+ */
+public class AnimalTest {
+    private final Animal model = new Animal();
+
+    /**
+     * Model tests for Animal
+     */
+    @Test
+    public void testAnimal() {
+        // TODO: test Animal
+    }
+
+    /**
+     * Test the property 'className'
+     */
+    @Test
+    public void classNameTest() {
+        // TODO: test className
+    }
+
+    /**
+     * Test the property 'color'
+     */
+    @Test
+    public void colorTest() {
+        // TODO: test color
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/ArrayOfArrayOfNumberOnlyTest.java

@@ -0,0 +1,53 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.math.BigDecimal;
+import java.util.ArrayList;
+import java.util.List;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for ArrayOfArrayOfNumberOnly
+ */
+public class ArrayOfArrayOfNumberOnlyTest {
+    private final ArrayOfArrayOfNumberOnly model = new ArrayOfArrayOfNumberOnly();
+
+    /**
+     * Model tests for ArrayOfArrayOfNumberOnly
+     */
+    @Test
+    public void testArrayOfArrayOfNumberOnly() {
+        // TODO: test ArrayOfArrayOfNumberOnly
+    }
+
+    /**
+     * Test the property 'arrayArrayNumber'
+     */
+    @Test
+    public void arrayArrayNumberTest() {
+        // TODO: test arrayArrayNumber
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/ArrayOfNumberOnlyTest.java

@@ -0,0 +1,53 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.math.BigDecimal;
+import java.util.ArrayList;
+import java.util.List;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for ArrayOfNumberOnly
+ */
+public class ArrayOfNumberOnlyTest {
+    private final ArrayOfNumberOnly model = new ArrayOfNumberOnly();
+
+    /**
+     * Model tests for ArrayOfNumberOnly
+     */
+    @Test
+    public void testArrayOfNumberOnly() {
+        // TODO: test ArrayOfNumberOnly
+    }
+
+    /**
+     * Test the property 'arrayNumber'
+     */
+    @Test
+    public void arrayNumberTest() {
+        // TODO: test arrayNumber
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/ArrayTestTest.java

@@ -0,0 +1,69 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.ArrayList;
+import java.util.List;
+import org.openapitools.client.model.ReadOnlyFirst;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for ArrayTest
+ */
+public class ArrayTestTest {
+    private final ArrayTest model = new ArrayTest();
+
+    /**
+     * Model tests for ArrayTest
+     */
+    @Test
+    public void testArrayTest() {
+        // TODO: test ArrayTest
+    }
+
+    /**
+     * Test the property 'arrayOfString'
+     */
+    @Test
+    public void arrayOfStringTest() {
+        // TODO: test arrayOfString
+    }
+
+    /**
+     * Test the property 'arrayArrayOfInteger'
+     */
+    @Test
+    public void arrayArrayOfIntegerTest() {
+        // TODO: test arrayArrayOfInteger
+    }
+
+    /**
+     * Test the property 'arrayArrayOfModel'
+     */
+    @Test
+    public void arrayArrayOfModelTest() {
+        // TODO: test arrayArrayOfModel
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/BigCatAllOfTest.java

@@ -0,0 +1,50 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for BigCatAllOf
+ */
+public class BigCatAllOfTest {
+    private final BigCatAllOf model = new BigCatAllOf();
+
+    /**
+     * Model tests for BigCatAllOf
+     */
+    @Test
+    public void testBigCatAllOf() {
+        // TODO: test BigCatAllOf
+    }
+
+    /**
+     * Test the property 'kind'
+     */
+    @Test
+    public void kindTest() {
+        // TODO: test kind
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/BigCatTest.java

@@ -0,0 +1,78 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.openapitools.client.model.BigCatAllOf;
+import org.openapitools.client.model.Cat;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for BigCat
+ */
+public class BigCatTest {
+    private final BigCat model = new BigCat();
+
+    /**
+     * Model tests for BigCat
+     */
+    @Test
+    public void testBigCat() {
+        // TODO: test BigCat
+    }
+
+    /**
+     * Test the property 'className'
+     */
+    @Test
+    public void classNameTest() {
+        // TODO: test className
+    }
+
+    /**
+     * Test the property 'color'
+     */
+    @Test
+    public void colorTest() {
+        // TODO: test color
+    }
+
+    /**
+     * Test the property 'declawed'
+     */
+    @Test
+    public void declawedTest() {
+        // TODO: test declawed
+    }
+
+    /**
+     * Test the property 'kind'
+     */
+    @Test
+    public void kindTest() {
+        // TODO: test kind
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/CapitalizationTest.java

@@ -0,0 +1,90 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for Capitalization
+ */
+public class CapitalizationTest {
+    private final Capitalization model = new Capitalization();
+
+    /**
+     * Model tests for Capitalization
+     */
+    @Test
+    public void testCapitalization() {
+        // TODO: test Capitalization
+    }
+
+    /**
+     * Test the property 'smallCamel'
+     */
+    @Test
+    public void smallCamelTest() {
+        // TODO: test smallCamel
+    }
+
+    /**
+     * Test the property 'capitalCamel'
+     */
+    @Test
+    public void capitalCamelTest() {
+        // TODO: test capitalCamel
+    }
+
+    /**
+     * Test the property 'smallSnake'
+     */
+    @Test
+    public void smallSnakeTest() {
+        // TODO: test smallSnake
+    }
+
+    /**
+     * Test the property 'capitalSnake'
+     */
+    @Test
+    public void capitalSnakeTest() {
+        // TODO: test capitalSnake
+    }
+
+    /**
+     * Test the property 'scAETHFlowPoints'
+     */
+    @Test
+    public void scAETHFlowPointsTest() {
+        // TODO: test scAETHFlowPoints
+    }
+
+    /**
+     * Test the property 'ATT_NAME'
+     */
+    @Test
+    public void ATT_NAMETest() {
+        // TODO: test ATT_NAME
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/CatAllOfTest.java

@@ -0,0 +1,50 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for CatAllOf
+ */
+public class CatAllOfTest {
+    private final CatAllOf model = new CatAllOf();
+
+    /**
+     * Model tests for CatAllOf
+     */
+    @Test
+    public void testCatAllOf() {
+        // TODO: test CatAllOf
+    }
+
+    /**
+     * Test the property 'declawed'
+     */
+    @Test
+    public void declawedTest() {
+        // TODO: test declawed
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/CatTest.java

@@ -0,0 +1,71 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.openapitools.client.model.Animal;
+import org.openapitools.client.model.BigCat;
+import org.openapitools.client.model.CatAllOf;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for Cat
+ */
+public class CatTest {
+    private final Cat model = new Cat();
+
+    /**
+     * Model tests for Cat
+     */
+    @Test
+    public void testCat() {
+        // TODO: test Cat
+    }
+
+    /**
+     * Test the property 'className'
+     */
+    @Test
+    public void classNameTest() {
+        // TODO: test className
+    }
+
+    /**
+     * Test the property 'color'
+     */
+    @Test
+    public void colorTest() {
+        // TODO: test color
+    }
+
+    /**
+     * Test the property 'declawed'
+     */
+    @Test
+    public void declawedTest() {
+        // TODO: test declawed
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/CategoryTest.java

@@ -0,0 +1,58 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for Category
+ */
+public class CategoryTest {
+    private final Category model = new Category();
+
+    /**
+     * Model tests for Category
+     */
+    @Test
+    public void testCategory() {
+        // TODO: test Category
+    }
+
+    /**
+     * Test the property 'id'
+     */
+    @Test
+    public void idTest() {
+        // TODO: test id
+    }
+
+    /**
+     * Test the property 'name'
+     */
+    @Test
+    public void nameTest() {
+        // TODO: test name
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/ClassModelTest.java

@@ -0,0 +1,50 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for ClassModel
+ */
+public class ClassModelTest {
+    private final ClassModel model = new ClassModel();
+
+    /**
+     * Model tests for ClassModel
+     */
+    @Test
+    public void testClassModel() {
+        // TODO: test ClassModel
+    }
+
+    /**
+     * Test the property 'propertyClass'
+     */
+    @Test
+    public void propertyClassTest() {
+        // TODO: test propertyClass
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/ClientTest.java

@@ -0,0 +1,50 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for Client
+ */
+public class ClientTest {
+    private final Client model = new Client();
+
+    /**
+     * Model tests for Client
+     */
+    @Test
+    public void testClient() {
+        // TODO: test Client
+    }
+
+    /**
+     * Test the property 'client'
+     */
+    @Test
+    public void clientTest() {
+        // TODO: test client
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/DogAllOfTest.java

@@ -0,0 +1,50 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for DogAllOf
+ */
+public class DogAllOfTest {
+    private final DogAllOf model = new DogAllOf();
+
+    /**
+     * Model tests for DogAllOf
+     */
+    @Test
+    public void testDogAllOf() {
+        // TODO: test DogAllOf
+    }
+
+    /**
+     * Test the property 'breed'
+     */
+    @Test
+    public void breedTest() {
+        // TODO: test breed
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/DogTest.java

@@ -0,0 +1,70 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.openapitools.client.model.Animal;
+import org.openapitools.client.model.DogAllOf;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for Dog
+ */
+public class DogTest {
+    private final Dog model = new Dog();
+
+    /**
+     * Model tests for Dog
+     */
+    @Test
+    public void testDog() {
+        // TODO: test Dog
+    }
+
+    /**
+     * Test the property 'className'
+     */
+    @Test
+    public void classNameTest() {
+        // TODO: test className
+    }
+
+    /**
+     * Test the property 'color'
+     */
+    @Test
+    public void colorTest() {
+        // TODO: test color
+    }
+
+    /**
+     * Test the property 'breed'
+     */
+    @Test
+    public void breedTest() {
+        // TODO: test breed
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/EnumArraysTest.java

@@ -0,0 +1,60 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.ArrayList;
+import java.util.List;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for EnumArrays
+ */
+public class EnumArraysTest {
+    private final EnumArrays model = new EnumArrays();
+
+    /**
+     * Model tests for EnumArrays
+     */
+    @Test
+    public void testEnumArrays() {
+        // TODO: test EnumArrays
+    }
+
+    /**
+     * Test the property 'justSymbol'
+     */
+    @Test
+    public void justSymbolTest() {
+        // TODO: test justSymbol
+    }
+
+    /**
+     * Test the property 'arrayEnum'
+     */
+    @Test
+    public void arrayEnumTest() {
+        // TODO: test arrayEnum
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/EnumClassTest.java

@@ -0,0 +1,33 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for EnumClass
+ */
+public class EnumClassTest {
+    /**
+     * Model tests for EnumClass
+     */
+    @Test
+    public void testEnumClass() {
+        // TODO: test EnumClass
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/EnumTestTest.java

@@ -0,0 +1,83 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.openapitools.client.model.OuterEnum;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for EnumTest
+ */
+public class EnumTestTest {
+    private final EnumTest model = new EnumTest();
+
+    /**
+     * Model tests for EnumTest
+     */
+    @Test
+    public void testEnumTest() {
+        // TODO: test EnumTest
+    }
+
+    /**
+     * Test the property 'enumString'
+     */
+    @Test
+    public void enumStringTest() {
+        // TODO: test enumString
+    }
+
+    /**
+     * Test the property 'enumStringRequired'
+     */
+    @Test
+    public void enumStringRequiredTest() {
+        // TODO: test enumStringRequired
+    }
+
+    /**
+     * Test the property 'enumInteger'
+     */
+    @Test
+    public void enumIntegerTest() {
+        // TODO: test enumInteger
+    }
+
+    /**
+     * Test the property 'enumNumber'
+     */
+    @Test
+    public void enumNumberTest() {
+        // TODO: test enumNumber
+    }
+
+    /**
+     * Test the property 'outerEnum'
+     */
+    @Test
+    public void outerEnumTest() {
+        // TODO: test outerEnum
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/FileSchemaTestClassTest.java

@@ -0,0 +1,60 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.ArrayList;
+import java.util.List;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for FileSchemaTestClass
+ */
+public class FileSchemaTestClassTest {
+    private final FileSchemaTestClass model = new FileSchemaTestClass();
+
+    /**
+     * Model tests for FileSchemaTestClass
+     */
+    @Test
+    public void testFileSchemaTestClass() {
+        // TODO: test FileSchemaTestClass
+    }
+
+    /**
+     * Test the property 'file'
+     */
+    @Test
+    public void fileTest() {
+        // TODO: test file
+    }
+
+    /**
+     * Test the property 'files'
+     */
+    @Test
+    public void filesTest() {
+        // TODO: test files
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/FormatTestTest.java

@@ -0,0 +1,159 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.io.File;
+import java.math.BigDecimal;
+import java.util.UUID;
+import org.threeten.bp.LocalDate;
+import org.threeten.bp.OffsetDateTime;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for FormatTest
+ */
+public class FormatTestTest {
+    private final FormatTest model = new FormatTest();
+
+    /**
+     * Model tests for FormatTest
+     */
+    @Test
+    public void testFormatTest() {
+        // TODO: test FormatTest
+    }
+
+    /**
+     * Test the property 'integer'
+     */
+    @Test
+    public void integerTest() {
+        // TODO: test integer
+    }
+
+    /**
+     * Test the property 'int32'
+     */
+    @Test
+    public void int32Test() {
+        // TODO: test int32
+    }
+
+    /**
+     * Test the property 'int64'
+     */
+    @Test
+    public void int64Test() {
+        // TODO: test int64
+    }
+
+    /**
+     * Test the property 'number'
+     */
+    @Test
+    public void numberTest() {
+        // TODO: test number
+    }
+
+    /**
+     * Test the property '_float'
+     */
+    @Test
+    public void _floatTest() {
+        // TODO: test _float
+    }
+
+    /**
+     * Test the property '_double'
+     */
+    @Test
+    public void _doubleTest() {
+        // TODO: test _double
+    }
+
+    /**
+     * Test the property 'string'
+     */
+    @Test
+    public void stringTest() {
+        // TODO: test string
+    }
+
+    /**
+     * Test the property '_byte'
+     */
+    @Test
+    public void _byteTest() {
+        // TODO: test _byte
+    }
+
+    /**
+     * Test the property 'binary'
+     */
+    @Test
+    public void binaryTest() {
+        // TODO: test binary
+    }
+
+    /**
+     * Test the property 'date'
+     */
+    @Test
+    public void dateTest() {
+        // TODO: test date
+    }
+
+    /**
+     * Test the property 'dateTime'
+     */
+    @Test
+    public void dateTimeTest() {
+        // TODO: test dateTime
+    }
+
+    /**
+     * Test the property 'uuid'
+     */
+    @Test
+    public void uuidTest() {
+        // TODO: test uuid
+    }
+
+    /**
+     * Test the property 'password'
+     */
+    @Test
+    public void passwordTest() {
+        // TODO: test password
+    }
+
+    /**
+     * Test the property 'bigDecimal'
+     */
+    @Test
+    public void bigDecimalTest() {
+        // TODO: test bigDecimal
+    }
+
+}

samples/client/petstore/java/feign-no-nullable/src/test/java/org/openapitools/client/model/HasOnlyReadOnlyTest.java

@@ -0,0 +1,58 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for HasOnlyReadOnly
+ */
+public class HasOnlyReadOnlyTest {
+    private final HasOnlyReadOnly model = new HasOnlyReadOnly();
+
+    /**
+     * Model tests for HasOnlyReadOnly
+     */
+    @Test
+    public void testHasOnlyReadOnly() {
+        // TODO: test HasOnlyReadOnly
+    }
+
+    /**
+     * Test the property 'bar'
+     */
+    @Test
+    public void barTest() {
+        // TODO: test bar
+    }
+
+    /**
+     * Test the property 'foo'
+     */
+    @Test
+    public void fooTest() {
+        // TODO: test foo
+    }
+
+}