Support for GSON Decoder in Java Feign Generator (#14254)

* Supporting Gson decoder in Feign

* Supporting Gson decoder in Feign

* Fixing test failures - and ensuring Jackson is used as the default if nothing selected (back compatible)

* Adding in sample files

* Updating docs

* Switching to echo server version

* Adding feign-gson to the github workflow

* Empty-Commit

samples/client/echo_api/java/feign-gson/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/echo_api/java/feign-gson/src/main/java/org/openapitools/client/ApiClient.java

@@ -0,0 +1,196 @@
+package org.openapitools.client;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+
+import feign.Feign;
+import feign.RequestInterceptor;
+import feign.form.FormEncoder;
+import feign.gson.GsonDecoder;
+import feign.gson.GsonEncoder;
+import feign.slf4j.Slf4jLogger;
+import org.openapitools.client.auth.HttpBasicAuth;
+import org.openapitools.client.auth.HttpBearerAuth;
+import org.openapitools.client.auth.ApiKeyAuth;
+
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class ApiClient {
+  private static final Logger log = Logger.getLogger(ApiClient.class.getName());
+
+  public interface Api {}
+
+  private String basePath = "http://localhost:3000";
+  private Map<String, RequestInterceptor> apiAuthorizations;
+  private Feign.Builder feignBuilder;
+
+  public ApiClient() {
+    apiAuthorizations = new LinkedHashMap<String, RequestInterceptor>();
+    feignBuilder = Feign.builder()
+        .encoder(new FormEncoder(new GsonEncoder()))
+        .decoder(new GsonDecoder())
+        .logger(new Slf4jLogger());
+  }
+
+  public ApiClient(String[] authNames) {
+    this();
+    for(String authName : authNames) {
+      log.log(Level.FINE, "Creating authentication {0}", authName);
+      throw new RuntimeException("auth name \"" + authName + "\" not found in available auth names");
+    }
+  }
+
+  /**
+   * 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);
+  }
+
+  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;
+  }
+
+
+
+
+  /**
+   * 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) {
+    HttpBearerAuth apiAuthorization =  getAuthorization(HttpBearerAuth.class);
+    apiAuthorization.setBearerToken(bearerToken);
+  }
+
+  /**
+   * Helper method to configure the first api key found
+   * @param apiKey API key
+   */
+  public void setApiKey(String apiKey) {
+    ApiKeyAuth apiAuthorization =  getAuthorization(ApiKeyAuth.class);
+    apiAuthorization.setApiKey(apiKey);
+  }
+
+  /**
+   * Helper method to configure the username/password for basic auth
+   * @param username Username
+   * @param password Password
+   */
+  public void setCredentials(String username, String password) {
+    HttpBasicAuth apiAuthorization = getAuthorization(HttpBasicAuth.class);
+    apiAuthorization.setCredentials(username, password);
+  }
+
+  /**
+   * Gets request interceptor based on authentication name
+   * @param authName Authentication 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);
+  }
+
+  private <T extends RequestInterceptor> T getAuthorization(Class<T> type) {
+    return (T) apiAuthorizations.values()
+                                .stream()
+                                .filter(requestInterceptor -> type.isAssignableFrom(requestInterceptor.getClass()))
+                                .findFirst()
+                                .orElseThrow(() -> new RuntimeException("No Oauth authentication or OAuth configured!"));
+    }
+}

samples/client/echo_api/java/feign-gson/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/echo_api/java/feign-gson/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 description 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 IllegalArgumentException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replace("{" + name + "}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/echo_api/java/feign-gson/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/echo_api/java/feign-gson/src/main/java/org/openapitools/client/StringUtil.java

@@ -0,0 +1,83 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * 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/echo_api/java/feign-gson/src/main/java/org/openapitools/client/api/BodyApi.java

@@ -0,0 +1,47 @@
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.EncodingUtils;
+import org.openapitools.client.model.ApiResponse;
+
+import org.openapitools.client.model.Pet;
+
+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 BodyApi extends ApiClient.Api {
+
+
+  /**
+   * Test body parameter(s)
+   * Test body parameter(s)
+   * @param pet Pet object that needs to be added to the store (optional)
+   * @return Pet
+   */
+  @RequestLine("POST /echo/body/Pet")
+  @Headers({
+    "Content-Type: application/json",
+    "Accept: application/json",
+  })
+  Pet testEchoBodyPet(Pet pet);
+
+  /**
+   * Test body parameter(s)
+   * Similar to <code>testEchoBodyPet</code> but it also returns the http response headers .
+   * Test body parameter(s)
+   * @param pet Pet object that needs to be added to the store (optional)
+   * @return A ApiResponse that wraps the response boyd and the http headers.
+   */
+  @RequestLine("POST /echo/body/Pet")
+  @Headers({
+    "Content-Type: application/json",
+    "Accept: application/json",
+  })
+  ApiResponse<Pet> testEchoBodyPetWithHttpInfo(Pet pet);
+
+
+}

samples/client/echo_api/java/feign-gson/src/main/java/org/openapitools/client/api/PathApi.java

@@ -0,0 +1,46 @@
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.EncodingUtils;
+import org.openapitools.client.model.ApiResponse;
+
+
+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 PathApi extends ApiClient.Api {
+
+
+  /**
+   * Test path parameter(s)
+   * Test path parameter(s)
+   * @param pathString  (required)
+   * @param pathInteger  (required)
+   * @return String
+   */
+  @RequestLine("GET /path/string/{pathString}/integer/{pathInteger}")
+  @Headers({
+    "Accept: text/plain",
+  })
+  String testsPathStringPathStringIntegerPathInteger(@Param("pathString") String pathString, @Param("pathInteger") Integer pathInteger);
+
+  /**
+   * Test path parameter(s)
+   * Similar to <code>testsPathStringPathStringIntegerPathInteger</code> but it also returns the http response headers .
+   * Test path parameter(s)
+   * @param pathString  (required)
+   * @param pathInteger  (required)
+   * @return A ApiResponse that wraps the response boyd and the http headers.
+   */
+  @RequestLine("GET /path/string/{pathString}/integer/{pathInteger}")
+  @Headers({
+    "Accept: text/plain",
+  })
+  ApiResponse<String> testsPathStringPathStringIntegerPathIntegerWithHttpInfo(@Param("pathString") String pathString, @Param("pathInteger") Integer pathInteger);
+
+
+}

samples/client/echo_api/java/feign-gson/src/main/java/org/openapitools/client/api/QueryApi.java

@@ -0,0 +1,266 @@
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.EncodingUtils;
+import org.openapitools.client.model.ApiResponse;
+
+import org.openapitools.client.model.Pet;
+import org.openapitools.client.model.TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter;
+
+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 QueryApi extends ApiClient.Api {
+
+
+  /**
+   * Test query parameter(s)
+   * Test query parameter(s)
+   * @param integerQuery  (optional)
+   * @param booleanQuery  (optional)
+   * @param stringQuery  (optional)
+   * @return String
+   */
+  @RequestLine("GET /query/integer/boolean/string?integer_query={integerQuery}&boolean_query={booleanQuery}&string_query={stringQuery}")
+  @Headers({
+    "Accept: text/plain",
+  })
+  String testQueryIntegerBooleanString(@Param("integerQuery") Integer integerQuery, @Param("booleanQuery") Boolean booleanQuery, @Param("stringQuery") String stringQuery);
+
+  /**
+   * Test query parameter(s)
+   * Similar to <code>testQueryIntegerBooleanString</code> but it also returns the http response headers .
+   * Test query parameter(s)
+   * @param integerQuery  (optional)
+   * @param booleanQuery  (optional)
+   * @param stringQuery  (optional)
+   * @return A ApiResponse that wraps the response boyd and the http headers.
+   */
+  @RequestLine("GET /query/integer/boolean/string?integer_query={integerQuery}&boolean_query={booleanQuery}&string_query={stringQuery}")
+  @Headers({
+    "Accept: text/plain",
+  })
+  ApiResponse<String> testQueryIntegerBooleanStringWithHttpInfo(@Param("integerQuery") Integer integerQuery, @Param("booleanQuery") Boolean booleanQuery, @Param("stringQuery") String stringQuery);
+
+
+  /**
+   * Test query parameter(s)
+   * Test query parameter(s)
+   * Note, this is equivalent to the other <code>testQueryIntegerBooleanString</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 TestQueryIntegerBooleanStringQueryParams} 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>integerQuery -  (optional)</li>
+   *   <li>booleanQuery -  (optional)</li>
+   *   <li>stringQuery -  (optional)</li>
+   *   </ul>
+   * @return String
+   */
+  @RequestLine("GET /query/integer/boolean/string?integer_query={integerQuery}&boolean_query={booleanQuery}&string_query={stringQuery}")
+  @Headers({
+  "Accept: text/plain",
+  })
+  String testQueryIntegerBooleanString(@QueryMap(encoded=true) Map<String, Object> queryParams);
+
+  /**
+  * Test query parameter(s)
+  * Test query parameter(s)
+  * Note, this is equivalent to the other <code>testQueryIntegerBooleanString</code> that receives the query parameters as a map,
+  * but this one also exposes the Http response headers
+      * @param queryParams Map of query parameters as name-value pairs
+      *   <p>The following elements may be specified in the query map:</p>
+      *   <ul>
+          *   <li>integerQuery -  (optional)</li>
+          *   <li>booleanQuery -  (optional)</li>
+          *   <li>stringQuery -  (optional)</li>
+      *   </ul>
+          * @return String
+      */
+      @RequestLine("GET /query/integer/boolean/string?integer_query={integerQuery}&boolean_query={booleanQuery}&string_query={stringQuery}")
+      @Headers({
+    "Accept: text/plain",
+      })
+   ApiResponse<String> testQueryIntegerBooleanStringWithHttpInfo(@QueryMap(encoded=true) Map<String, Object> queryParams);
+
+
+   /**
+   * A convenience class for generating query parameters for the
+   * <code>testQueryIntegerBooleanString</code> method in a fluent style.
+   */
+  public static class TestQueryIntegerBooleanStringQueryParams extends HashMap<String, Object> {
+    public TestQueryIntegerBooleanStringQueryParams integerQuery(final Integer value) {
+      put("integer_query", EncodingUtils.encode(value));
+      return this;
+    }
+    public TestQueryIntegerBooleanStringQueryParams booleanQuery(final Boolean value) {
+      put("boolean_query", EncodingUtils.encode(value));
+      return this;
+    }
+    public TestQueryIntegerBooleanStringQueryParams stringQuery(final String value) {
+      put("string_query", EncodingUtils.encode(value));
+      return this;
+    }
+  }
+
+  /**
+   * Test query parameter(s)
+   * Test query parameter(s)
+   * @param queryObject  (optional)
+   * @return String
+   */
+  @RequestLine("GET /query/style_form/explode_true/array_string?query_object={queryObject}")
+  @Headers({
+    "Accept: text/plain",
+  })
+  String testQueryStyleFormExplodeTrueArrayString(@Param("queryObject") TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter queryObject);
+
+  /**
+   * Test query parameter(s)
+   * Similar to <code>testQueryStyleFormExplodeTrueArrayString</code> but it also returns the http response headers .
+   * Test query parameter(s)
+   * @param queryObject  (optional)
+   * @return A ApiResponse that wraps the response boyd and the http headers.
+   */
+  @RequestLine("GET /query/style_form/explode_true/array_string?query_object={queryObject}")
+  @Headers({
+    "Accept: text/plain",
+  })
+  ApiResponse<String> testQueryStyleFormExplodeTrueArrayStringWithHttpInfo(@Param("queryObject") TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter queryObject);
+
+
+  /**
+   * Test query parameter(s)
+   * Test query parameter(s)
+   * Note, this is equivalent to the other <code>testQueryStyleFormExplodeTrueArrayString</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 TestQueryStyleFormExplodeTrueArrayStringQueryParams} 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>queryObject -  (optional)</li>
+   *   </ul>
+   * @return String
+   */
+  @RequestLine("GET /query/style_form/explode_true/array_string?query_object={queryObject}")
+  @Headers({
+  "Accept: text/plain",
+  })
+  String testQueryStyleFormExplodeTrueArrayString(@QueryMap(encoded=true) Map<String, Object> queryParams);
+
+  /**
+  * Test query parameter(s)
+  * Test query parameter(s)
+  * Note, this is equivalent to the other <code>testQueryStyleFormExplodeTrueArrayString</code> that receives the query parameters as a map,
+  * but this one also exposes the Http response headers
+      * @param queryParams Map of query parameters as name-value pairs
+      *   <p>The following elements may be specified in the query map:</p>
+      *   <ul>
+          *   <li>queryObject -  (optional)</li>
+      *   </ul>
+          * @return String
+      */
+      @RequestLine("GET /query/style_form/explode_true/array_string?query_object={queryObject}")
+      @Headers({
+    "Accept: text/plain",
+      })
+   ApiResponse<String> testQueryStyleFormExplodeTrueArrayStringWithHttpInfo(@QueryMap(encoded=true) Map<String, Object> queryParams);
+
+
+   /**
+   * A convenience class for generating query parameters for the
+   * <code>testQueryStyleFormExplodeTrueArrayString</code> method in a fluent style.
+   */
+  public static class TestQueryStyleFormExplodeTrueArrayStringQueryParams extends HashMap<String, Object> {
+    public TestQueryStyleFormExplodeTrueArrayStringQueryParams queryObject(final TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter value) {
+      put("query_object", EncodingUtils.encode(value));
+      return this;
+    }
+  }
+
+  /**
+   * Test query parameter(s)
+   * Test query parameter(s)
+   * @param queryObject  (optional)
+   * @return String
+   */
+  @RequestLine("GET /query/style_form/explode_true/object?query_object={queryObject}")
+  @Headers({
+    "Accept: text/plain",
+  })
+  String testQueryStyleFormExplodeTrueObject(@Param("queryObject") Pet queryObject);
+
+  /**
+   * Test query parameter(s)
+   * Similar to <code>testQueryStyleFormExplodeTrueObject</code> but it also returns the http response headers .
+   * Test query parameter(s)
+   * @param queryObject  (optional)
+   * @return A ApiResponse that wraps the response boyd and the http headers.
+   */
+  @RequestLine("GET /query/style_form/explode_true/object?query_object={queryObject}")
+  @Headers({
+    "Accept: text/plain",
+  })
+  ApiResponse<String> testQueryStyleFormExplodeTrueObjectWithHttpInfo(@Param("queryObject") Pet queryObject);
+
+
+  /**
+   * Test query parameter(s)
+   * Test query parameter(s)
+   * Note, this is equivalent to the other <code>testQueryStyleFormExplodeTrueObject</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 TestQueryStyleFormExplodeTrueObjectQueryParams} 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>queryObject -  (optional)</li>
+   *   </ul>
+   * @return String
+   */
+  @RequestLine("GET /query/style_form/explode_true/object?query_object={queryObject}")
+  @Headers({
+  "Accept: text/plain",
+  })
+  String testQueryStyleFormExplodeTrueObject(@QueryMap(encoded=true) Map<String, Object> queryParams);
+
+  /**
+  * Test query parameter(s)
+  * Test query parameter(s)
+  * Note, this is equivalent to the other <code>testQueryStyleFormExplodeTrueObject</code> that receives the query parameters as a map,
+  * but this one also exposes the Http response headers
+      * @param queryParams Map of query parameters as name-value pairs
+      *   <p>The following elements may be specified in the query map:</p>
+      *   <ul>
+          *   <li>queryObject -  (optional)</li>
+      *   </ul>
+          * @return String
+      */
+      @RequestLine("GET /query/style_form/explode_true/object?query_object={queryObject}")
+      @Headers({
+    "Accept: text/plain",
+      })
+   ApiResponse<String> testQueryStyleFormExplodeTrueObjectWithHttpInfo(@QueryMap(encoded=true) Map<String, Object> queryParams);
+
+
+   /**
+   * A convenience class for generating query parameters for the
+   * <code>testQueryStyleFormExplodeTrueObject</code> method in a fluent style.
+   */
+  public static class TestQueryStyleFormExplodeTrueObjectQueryParams extends HashMap<String, Object> {
+    public TestQueryStyleFormExplodeTrueObjectQueryParams queryObject(final Pet value) {
+      put("query_object", EncodingUtils.encode(value));
+      return this;
+    }
+  }
+}

samples/client/echo_api/java/feign-gson/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/echo_api/java/feign-gson/src/main/java/org/openapitools/client/auth/DefaultApi20Impl.java

@@ -0,0 +1,47 @@
+package org.openapitools.client.auth;
+
+import com.github.scribejava.core.builder.api.DefaultApi20;
+import com.github.scribejava.core.extractors.OAuth2AccessTokenJsonExtractor;
+import com.github.scribejava.core.extractors.TokenExtractor;
+import com.github.scribejava.core.model.OAuth2AccessToken;
+import com.github.scribejava.core.oauth2.bearersignature.BearerSignature;
+import com.github.scribejava.core.oauth2.bearersignature.BearerSignatureURIQueryParameter;
+import com.github.scribejava.core.oauth2.clientauthentication.ClientAuthentication;
+import com.github.scribejava.core.oauth2.clientauthentication.RequestBodyAuthenticationScheme;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class DefaultApi20Impl extends DefaultApi20 {
+
+    private final String accessTokenEndpoint;
+    private final String authorizationBaseUrl;
+
+    protected DefaultApi20Impl(String authorizationBaseUrl, String accessTokenEndpoint) {
+        this.authorizationBaseUrl = authorizationBaseUrl;
+        this.accessTokenEndpoint = accessTokenEndpoint;
+    }
+
+    @Override
+    public String getAccessTokenEndpoint() {
+        return accessTokenEndpoint;
+    }
+
+    @Override
+    protected String getAuthorizationBaseUrl() {
+        return authorizationBaseUrl;
+    }
+
+    @Override
+    public BearerSignature getBearerSignature() {
+        return BearerSignatureURIQueryParameter.instance();
+    }
+
+    @Override
+    public ClientAuthentication getClientAuthentication() {
+        return RequestBodyAuthenticationScheme.instance();
+    }
+
+    @Override
+    public TokenExtractor<OAuth2AccessToken> getAccessTokenExtractor() {
+        return OAuth2AccessTokenJsonExtractor.instance();
+    }
+}

samples/client/echo_api/java/feign-gson/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/echo_api/java/feign-gson/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/echo_api/java/feign-gson/src/main/java/org/openapitools/client/model/ApiResponse.java

@@ -0,0 +1,43 @@
+package org.openapitools.client.model;
+
+import java.util.Map;
+import java.util.List;
+
+public class ApiResponse<T>{
+
+    final private int statusCode;
+    final private Map<String, List<String>> headers;
+    final private T data;
+
+    /**
+     * @param statusCode The status code of HTTP response
+     * @param headers The headers of HTTP response
+     */
+    public ApiResponse(int statusCode, Map<String, List<String>> headers) {
+        this(statusCode, headers, null);
+    }
+
+    /**
+     * @param statusCode The status code of HTTP response
+     * @param headers The headers of HTTP response
+     * @param data The object deserialized from response bod
+     */
+    public ApiResponse(int statusCode, Map<String, List<String>> headers, T data) {
+        this.statusCode = statusCode;
+        this.headers = headers;
+        this.data = data;
+    }
+
+    public int getStatusCode() {
+        return statusCode;
+    }
+
+    public Map<String, List<String>> getHeaders() {
+        return headers;
+    }
+
+    public T getData() {
+        return data;
+    }
+  
+}

samples/client/echo_api/java/feign-gson/src/main/java/org/openapitools/client/model/Category.java

@@ -0,0 +1,125 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * 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.google.gson.TypeAdapter;
+import com.google.gson.annotations.JsonAdapter;
+import com.google.gson.annotations.SerializedName;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+import java.io.IOException;
+
+/**
+ * Category
+ */
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Category {
+  public static final String SERIALIZED_NAME_ID = "id";
+  @SerializedName(SERIALIZED_NAME_ID)
+  private Long id;
+
+  public static final String SERIALIZED_NAME_NAME = "name";
+  @SerializedName(SERIALIZED_NAME_NAME)
+  private String name;
+
+  public Category() {
+  }
+
+  public Category id(Long id) {
+    
+    this.id = id;
+    return this;
+  }
+
+   /**
+   * Get id
+   * @return id
+  **/
+  @javax.annotation.Nullable
+
+  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
+  **/
+  @javax.annotation.Nullable
+
+  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/echo_api/java/feign-gson/src/main/java/org/openapitools/client/model/Pet.java

@@ -0,0 +1,303 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * 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.google.gson.TypeAdapter;
+import com.google.gson.annotations.JsonAdapter;
+import com.google.gson.annotations.SerializedName;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import org.openapitools.client.model.Category;
+import org.openapitools.client.model.Tag;
+
+/**
+ * Pet
+ */
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Pet {
+  public static final String SERIALIZED_NAME_ID = "id";
+  @SerializedName(SERIALIZED_NAME_ID)
+  private Long id;
+
+  public static final String SERIALIZED_NAME_NAME = "name";
+  @SerializedName(SERIALIZED_NAME_NAME)
+  private String name;
+
+  public static final String SERIALIZED_NAME_CATEGORY = "category";
+  @SerializedName(SERIALIZED_NAME_CATEGORY)
+  private Category category;
+
+  public static final String SERIALIZED_NAME_PHOTO_URLS = "photoUrls";
+  @SerializedName(SERIALIZED_NAME_PHOTO_URLS)
+  private List<String> photoUrls = new ArrayList<>();
+
+  public static final String SERIALIZED_NAME_TAGS = "tags";
+  @SerializedName(SERIALIZED_NAME_TAGS)
+  private List<Tag> tags = null;
+
+  /**
+   * pet status in the store
+   */
+  @JsonAdapter(StatusEnum.Adapter.class)
+  public enum StatusEnum {
+    AVAILABLE("available"),
+    
+    PENDING("pending"),
+    
+    SOLD("sold");
+
+    private String value;
+
+    StatusEnum(String value) {
+      this.value = value;
+    }
+
+    public String getValue() {
+      return value;
+    }
+
+    @Override
+    public String toString() {
+      return String.valueOf(value);
+    }
+
+    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 class Adapter extends TypeAdapter<StatusEnum> {
+      @Override
+      public void write(final JsonWriter jsonWriter, final StatusEnum enumeration) throws IOException {
+        jsonWriter.value(enumeration.getValue());
+      }
+
+      @Override
+      public StatusEnum read(final JsonReader jsonReader) throws IOException {
+        String value =  jsonReader.nextString();
+        return StatusEnum.fromValue(value);
+      }
+    }
+  }
+
+  public static final String SERIALIZED_NAME_STATUS = "status";
+  @SerializedName(SERIALIZED_NAME_STATUS)
+  private StatusEnum status;
+
+  public Pet() {
+  }
+
+  public Pet id(Long id) {
+    
+    this.id = id;
+    return this;
+  }
+
+   /**
+   * Get id
+   * @return id
+  **/
+  @javax.annotation.Nullable
+
+  public Long getId() {
+    return id;
+  }
+
+
+  public void setId(Long id) {
+    this.id = id;
+  }
+
+
+  public Pet name(String name) {
+    
+    this.name = name;
+    return this;
+  }
+
+   /**
+   * Get name
+   * @return name
+  **/
+  @javax.annotation.Nonnull
+
+  public String getName() {
+    return name;
+  }
+
+
+  public void setName(String name) {
+    this.name = name;
+  }
+
+
+  public Pet category(Category category) {
+    
+    this.category = category;
+    return this;
+  }
+
+   /**
+   * Get category
+   * @return category
+  **/
+  @javax.annotation.Nullable
+
+  public Category getCategory() {
+    return category;
+  }
+
+
+  public void setCategory(Category category) {
+    this.category = category;
+  }
+
+
+  public Pet photoUrls(List<String> photoUrls) {
+    
+    this.photoUrls = photoUrls;
+    return this;
+  }
+
+  public Pet addPhotoUrlsItem(String photoUrlsItem) {
+    this.photoUrls.add(photoUrlsItem);
+    return this;
+  }
+
+   /**
+   * Get photoUrls
+   * @return photoUrls
+  **/
+  @javax.annotation.Nonnull
+
+  public List<String> getPhotoUrls() {
+    return photoUrls;
+  }
+
+
+  public void setPhotoUrls(List<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<>();
+    }
+    this.tags.add(tagsItem);
+    return this;
+  }
+
+   /**
+   * Get tags
+   * @return tags
+  **/
+  @javax.annotation.Nullable
+
+  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
+
+  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.name, pet.name) &&
+        Objects.equals(this.category, pet.category) &&
+        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, name, category, 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("    name: ").append(toIndentedString(name)).append("\n");
+    sb.append("    category: ").append(toIndentedString(category)).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/echo_api/java/feign-gson/src/main/java/org/openapitools/client/model/Tag.java

@@ -0,0 +1,125 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * 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.google.gson.TypeAdapter;
+import com.google.gson.annotations.JsonAdapter;
+import com.google.gson.annotations.SerializedName;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+import java.io.IOException;
+
+/**
+ * Tag
+ */
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Tag {
+  public static final String SERIALIZED_NAME_ID = "id";
+  @SerializedName(SERIALIZED_NAME_ID)
+  private Long id;
+
+  public static final String SERIALIZED_NAME_NAME = "name";
+  @SerializedName(SERIALIZED_NAME_NAME)
+  private String name;
+
+  public Tag() {
+  }
+
+  public Tag id(Long id) {
+    
+    this.id = id;
+    return this;
+  }
+
+   /**
+   * Get id
+   * @return id
+  **/
+  @javax.annotation.Nullable
+
+  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
+
+  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/echo_api/java/feign-gson/src/main/java/org/openapitools/client/model/TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter.java

@@ -0,0 +1,107 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * 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.google.gson.TypeAdapter;
+import com.google.gson.annotations.JsonAdapter;
+import com.google.gson.annotations.SerializedName;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter
+ */
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter {
+  public static final String SERIALIZED_NAME_VALUES = "values";
+  @SerializedName(SERIALIZED_NAME_VALUES)
+  private List<String> values = null;
+
+  public TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter() {
+  }
+
+  public TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter values(List<String> values) {
+    
+    this.values = values;
+    return this;
+  }
+
+  public TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter addValuesItem(String valuesItem) {
+    if (this.values == null) {
+      this.values = new ArrayList<>();
+    }
+    this.values.add(valuesItem);
+    return this;
+  }
+
+   /**
+   * Get values
+   * @return values
+  **/
+  @javax.annotation.Nullable
+
+  public List<String> getValues() {
+    return values;
+  }
+
+
+  public void setValues(List<String> values) {
+    this.values = values;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter testQueryStyleFormExplodeTrueArrayStringQueryObjectParameter = (TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter) o;
+    return Objects.equals(this.values, testQueryStyleFormExplodeTrueArrayStringQueryObjectParameter.values);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(values);
+  }
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter {\n");
+    sb.append("    values: ").append(toIndentedString(values)).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    ");
+  }
+
+}
+