Add full OAuth2 support to jersey2-experimental codegen (#6183)

* Add full Oauth2 support to Jersey client

* Regenerate jersey2-experimental sample

* Regenerate all java clients

modules/openapi-generator/src/main/resources/Java/StringUtil.mustache

@@ -2,6 +2,9 @@
 
 package {{invokerPackage}};
 
+import java.util.Collection;
+import java.util.Iterator;
+
 {{>generatedAnnotation}}
 public class StringUtil {
   /**
@@ -47,4 +50,23 @@ public class StringUtil {
     }
     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();
+  }
 }

modules/openapi-generator/src/main/resources/Java/libraries/jersey2-experimental/ApiClient.mustache

@@ -11,6 +11,9 @@ import javax.ws.rs.core.MediaType;
 import javax.ws.rs.core.Response;
 import javax.ws.rs.core.Response.Status;
 
+{{#hasOAuthMethods}}
+import com.github.scribejava.core.model.OAuth2AccessToken;
+{{/hasOAuthMethods}}
 import org.glassfish.jersey.client.ClientConfig;
 import org.glassfish.jersey.client.ClientProperties;
 import org.glassfish.jersey.client.HttpUrlConnectorProvider;
@@ -43,7 +46,6 @@ import java.util.List;
 import java.util.Arrays;
 import java.util.ArrayList;
 import java.util.Date;
-import java.util.TimeZone;
 
 import java.net.URLEncoder;
 
@@ -59,11 +61,10 @@ import {{invokerPackage}}.auth.HttpBasicAuth;
 import {{invokerPackage}}.auth.HttpBearerAuth;
 import {{invokerPackage}}.auth.HttpSignatureAuth;
 import {{invokerPackage}}.auth.ApiKeyAuth;
-import {{invokerPackage}}.model.AbstractOpenApiSchema;
-
 {{#hasOAuthMethods}}
 import {{invokerPackage}}.auth.OAuth;
 {{/hasOAuthMethods}}
+import {{invokerPackage}}.model.AbstractOpenApiSchema;
 
 {{>generatedAnnotation}}
 public class ApiClient {
@@ -178,7 +179,7 @@ public class ApiClient {
     authentications.put("{{name}}", new ApiKeyAuth({{#isKeyInHeader}}"header"{{/isKeyInHeader}}{{^isKeyInHeader}}"query"{{/isKeyInHeader}}, "{{keyParamName}}"));
     {{/isApiKey}}
     {{#isOAuth}}
-    authentications.put("{{name}}", new OAuth());
+    authentications.put("{{name}}", new OAuth(basePath, "{{tokenUrl}}"));
     {{/isOAuth}}
     {{/authMethods}}
     // Prevent the authentications from being modified.
@@ -191,6 +192,7 @@ public class ApiClient {
 
   /**
    * Gets the JSON instance to do JSON serialization and deserialization.
+   *
    * @return JSON
    */
   public JSON getJSON() {
@@ -212,6 +214,7 @@ public class ApiClient {
 
   public ApiClient setBasePath(String basePath) {
     this.basePath = basePath;
+    setOauthBasePath(basePath);
     return this;
   }
 
@@ -221,6 +224,7 @@ public class ApiClient {
 
   public ApiClient setServers(List<ServerConfiguration> servers) {
     this.servers = servers;
+    updateBasePath();
     return this;
   }
 
@@ -230,6 +234,7 @@ public class ApiClient {
 
   public ApiClient setServerIndex(Integer serverIndex) {
     this.serverIndex = serverIndex;
+    updateBasePath();
     return this;
   }
 
@@ -239,11 +244,25 @@ public class ApiClient {
 
   public ApiClient setServerVariables(Map<String, String> serverVariables) {
     this.serverVariables = serverVariables;
+    updateBasePath();
     return this;
   }
 
+  private void updateBasePath() {
+    setBasePath(servers.get(serverIndex).URL(serverVariables));
+  }
+
+  private void setOauthBasePath(String basePath) {
+    for(Authentication auth : authentications.values()) {
+      if (auth instanceof OAuth) {
+        ((OAuth) auth).setBasePath(basePath);
+      }
+    }
+  }
+
   /**
    * Get authentications (key: authentication name, value: authentication).
+   *
    * @return Map of authentication object
    */
   public Map<String, Authentication> getAuthentications() {
@@ -262,13 +281,14 @@ public class ApiClient {
 
   /**
    * Helper method to set username for the first HTTP basic authentication.
+   *
    * @param username Username
    */
-  public void setUsername(String username) {
+  public ApiClient setUsername(String username) {
     for (Authentication auth : authentications.values()) {
       if (auth instanceof HttpBasicAuth) {
         ((HttpBasicAuth) auth).setUsername(username);
-        return;
+        return this;
       }
     }
     throw new RuntimeException("No HTTP basic authentication configured!");
@@ -276,13 +296,14 @@ public class ApiClient {
 
   /**
    * Helper method to set password for the first HTTP basic authentication.
+   *
    * @param password Password
    */
-  public void setPassword(String password) {
+  public ApiClient setPassword(String password) {
     for (Authentication auth : authentications.values()) {
       if (auth instanceof HttpBasicAuth) {
         ((HttpBasicAuth) auth).setPassword(password);
-        return;
+        return this;
       }
     }
     throw new RuntimeException("No HTTP basic authentication configured!");
@@ -290,13 +311,14 @@ public class ApiClient {
 
   /**
    * Helper method to set API key value for the first API key authentication.
+   *
    * @param apiKey API key
    */
-  public void setApiKey(String apiKey) {
+  public ApiClient setApiKey(String apiKey) {
     for (Authentication auth : authentications.values()) {
       if (auth instanceof ApiKeyAuth) {
         ((ApiKeyAuth) auth).setApiKey(apiKey);
-        return;
+        return this;
       }
     }
     throw new RuntimeException("No API key authentication configured!");
@@ -307,29 +329,31 @@ public class ApiClient {
    *
    * @param secrets Hash map from authentication name to its secret.
    */
-  public void configureApiKeys(HashMap<String, String> secrets) {
+  public ApiClient configureApiKeys(HashMap<String, String> secrets) {
     for (Map.Entry<String, Authentication> authEntry : authentications.entrySet()) {
       Authentication auth = authEntry.getValue();
       if (auth instanceof ApiKeyAuth) {
         String name = authEntry.getKey();
         // respect x-auth-id-alias property
-        name = authenticationLookup.getOrDefault(name, name);
+        name = authenticationLookup.containsKey(name) ? authenticationLookup.get(name) : name;
         if (secrets.containsKey(name)) {
           ((ApiKeyAuth) auth).setApiKey(secrets.get(name));
         }
       }
     }
+    return this;
   }
 
   /**
    * Helper method to set API key prefix for the first API key authentication.
+   *
    * @param apiKeyPrefix API key prefix
    */
-  public void setApiKeyPrefix(String apiKeyPrefix) {
+  public ApiClient setApiKeyPrefix(String apiKeyPrefix) {
     for (Authentication auth : authentications.values()) {
       if (auth instanceof ApiKeyAuth) {
         ((ApiKeyAuth) auth).setApiKeyPrefix(apiKeyPrefix);
-        return;
+        return this;
       }
     }
     throw new RuntimeException("No API key authentication configured!");
@@ -337,28 +361,92 @@ public class ApiClient {
 
   /**
    * Helper method to set bearer token for the first Bearer authentication.
+   *
    * @param bearerToken Bearer token
    */
-  public void setBearerToken(String bearerToken) {
+  public ApiClient setBearerToken(String bearerToken) {
     for (Authentication auth : authentications.values()) {
       if (auth instanceof HttpBearerAuth) {
         ((HttpBearerAuth) auth).setBearerToken(bearerToken);
-        return;
+        return this;
       }
     }
     throw new RuntimeException("No Bearer authentication configured!");
   }
 
+
   {{#hasOAuthMethods}}
   /**
    * Helper method to set access token for the first OAuth2 authentication.
    * @param accessToken Access token
    */
-  public void setAccessToken(String accessToken) {
+  public ApiClient setAccessToken(String accessToken) {
     for (Authentication auth : authentications.values()) {
       if (auth instanceof OAuth) {
         ((OAuth) auth).setAccessToken(accessToken);
-        return;
+        return this;
+      }
+    }
+    throw new RuntimeException("No OAuth2 authentication configured!");
+  }
+
+  /**
+   * Helper method to set the credentials for the first OAuth2 authentication.
+   *
+   * @param clientId the client ID
+   * @param clientSecret the client secret
+   */
+  public ApiClient setOauthCredentials(String clientId, String clientSecret) {
+    for (Authentication auth : authentications.values()) {
+      if (auth instanceof OAuth) {
+        ((OAuth) auth).setCredentials(clientId, clientSecret);
+        return this;
+      }
+    }
+    throw new RuntimeException("No OAuth2 authentication configured!");
+  }
+
+  /**
+   * Helper method to set the password flow for the first OAuth2 authentication.
+   *
+   * @param username the user name
+   * @param password the user password
+   */
+  public ApiClient setOauthPasswordFlow(String username, String password) {
+    for (Authentication auth : authentications.values()) {
+      if (auth instanceof OAuth) {
+        ((OAuth) auth).usePasswordFlow(username, password);
+        return this;
+      }
+    }
+    throw new RuntimeException("No OAuth2 authentication configured!");
+  }
+
+  /**
+   * Helper method to set the authorization code flow for the first OAuth2 authentication.
+   *
+   * @param code the authorization code
+   */
+  public ApiClient setOauthAuthorizationCodeFlow(String code) {
+    for (Authentication auth : authentications.values()) {
+      if (auth instanceof OAuth) {
+        ((OAuth) auth).useAuthorizationCodeFlow(code);
+        return this;
+      }
+    }
+    throw new RuntimeException("No OAuth2 authentication configured!");
+  }
+
+  /**
+   * Helper method to set the scopes for the first OAuth2 authentication.
+   *
+   * @param scope the oauth scope
+   */
+  public ApiClient setOauthScope(String scope) {
+    for (Authentication auth : authentications.values()) {
+      if (auth instanceof OAuth) {
+        ((OAuth) auth).setScope(scope);
+        return this;
       }
     }
     throw new RuntimeException("No OAuth2 authentication configured!");
@@ -787,9 +875,9 @@ public class ApiClient {
     }
 
     if (matchCounter > 1 && "oneOf".equals(schema.getSchemaType())) {// more than 1 match for oneOf
-      throw new ApiException("Response body is invalid as it matches more than one schema (" + String.join(", ", matchSchemas) + ") defined in the oneOf model: " + schema.getClass().getName());
+      throw new ApiException("Response body is invalid as it matches more than one schema (" + StringUtil.join(matchSchemas, ", ") + ") defined in the oneOf model: " + schema.getClass().getName());
     } else if (matchCounter == 0) { // fail to match any in oneOf/anyOf schemas
-      throw new ApiException("Response body is invalid as it doens't match any schemas (" + String.join(", ", schema.getSchemas().keySet()) + ") defined in the oneOf/anyOf model: " + schema.getClass().getName());
+      throw new ApiException("Response body is invalid as it doens't match any schemas (" + StringUtil.join(schema.getSchemas().keySet(), ", ") + ") defined in the oneOf/anyOf model: " + schema.getClass().getName());
     } else { // only one matched
       schema.setActualInstance(result);
       return schema;
@@ -910,29 +998,35 @@ public class ApiClient {
    * @return The response body in type of string
    * @throws ApiException API exception
    */
-  public <T> ApiResponse<T> invokeAPI(String operation, String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, String> cookieParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames, GenericType<T> returnType, AbstractOpenApiSchema schema) throws ApiException {
+  public <T> ApiResponse<T> invokeAPI(
+      String operation,
+      String path,
+      String method,
+      List<Pair> queryParams,
+      Object body,
+      Map<String, String> headerParams,
+      Map<String, String> cookieParams,
+      Map<String, Object> formParams,
+      String accept,
+      String contentType,
+      String[] authNames,
+      GenericType<T> returnType,
+      AbstractOpenApiSchema schema)
+      throws ApiException {
 
     // Not using `.target(targetURL).path(path)` below,
     // to support (constant) query string in `path`, e.g. "/posts?draft=1"
     String targetURL;
-    if (serverIndex != null) {
-      Integer index;
-      List<ServerConfiguration> serverConfigurations;
-      Map<String, String> variables;
-
-      if (operationServers.containsKey(operation)) {
-        index = operationServerIndex.getOrDefault(operation, serverIndex);
-        variables = operationServerVariables.getOrDefault(operation, serverVariables);
-        serverConfigurations = operationServers.get(operation);
-      } else {
-        index = serverIndex;
-        variables = serverVariables;
-        serverConfigurations = servers;
-      }
+    if (operationServers.containsKey(operation)) {
+      Integer index = operationServerIndex.containsKey(operation) ? operationServerIndex.get(operation) : serverIndex;
+      Map<String, String> variables = operationServerVariables.containsKey(operation) ?
+        operationServerVariables.get(operation) : serverVariables;
+      List<ServerConfiguration> serverConfigurations = operationServers.get(operation);
       if (index < 0 || index >= serverConfigurations.size()) {
-        throw new ArrayIndexOutOfBoundsException(String.format(
-          "Invalid index %d when selecting the host settings. Must be less than %d", index, serverConfigurations.size()
-        ));
+        throw new ArrayIndexOutOfBoundsException(
+            String.format(
+                "Invalid index %d when selecting the host settings. Must be less than %d",
+                index, serverConfigurations.size()));
       }
       targetURL = serverConfigurations.get(index).URL(variables) + path;
     } else {
@@ -950,13 +1044,6 @@ public class ApiClient {
 
     Invocation.Builder invocationBuilder = target.request().accept(accept);
 
-    for (Entry<String, String> entry : headerParams.entrySet()) {
-      String value = entry.getValue();
-      if (value != null) {
-        invocationBuilder = invocationBuilder.header(entry.getKey(), value);
-      }
-    }
-
     for (Entry<String, String> entry : cookieParams.entrySet()) {
       String value = entry.getValue();
       if (value != null) {
@@ -971,63 +1058,63 @@ public class ApiClient {
       }
     }
 
-    for (Entry<String, String> entry : defaultHeaderMap.entrySet()) {
-      String key = entry.getKey();
-      if (!headerParams.containsKey(key)) {
-        String value = entry.getValue();
-        if (value != null) {
-          invocationBuilder = invocationBuilder.header(key, value);
-        }
-      }
-    }
-
     Entity<?> entity = serialize(body, formParams, contentType);
 
     // put all headers in one place
-    Map<String, String> allHeaderParams = new HashMap<>();
-    allHeaderParams.putAll(defaultHeaderMap);
+    Map<String, String> allHeaderParams = new HashMap<>(defaultHeaderMap);
     allHeaderParams.putAll(headerParams);
-   
+
     // update different parameters (e.g. headers) for authentication
-    updateParamsForAuth(authNames, queryParams, allHeaderParams, cookieParams, serializeToString(body, formParams, contentType), method, target.getUri());
+    updateParamsForAuth(
+        authNames,
+        queryParams,
+        allHeaderParams,
+        cookieParams,
+        serializeToString(body, formParams, contentType),
+        method,
+        target.getUri());
+
+    for (Entry<String, String> entry : allHeaderParams.entrySet()) {
+      String value = entry.getValue();
+      if (value != null) {
+        invocationBuilder = invocationBuilder.header(entry.getKey(), value);
+      }
+    }
 
     Response response = null;
 
     try {
-      if ("GET".equals(method)) {
-        response = invocationBuilder.get();
-      } else if ("POST".equals(method)) {
-        response = invocationBuilder.post(entity);
-      } else if ("PUT".equals(method)) {
-        response = invocationBuilder.put(entity);
-      } else if ("DELETE".equals(method)) {
-        response = invocationBuilder.method("DELETE", entity);
-      } else if ("PATCH".equals(method)) {
-        response = invocationBuilder.method("PATCH", entity);
-      } else if ("HEAD".equals(method)) {
-        response = invocationBuilder.head();
-      } else if ("OPTIONS".equals(method)) {
-        response = invocationBuilder.options();
-      } else if ("TRACE".equals(method)) {
-        response = invocationBuilder.trace();
-      } else {
-        throw new ApiException(500, "unknown method type " + method);
+      response = sendRequest(method, invocationBuilder, entity);
+
+      // If OAuth is used and a status 401 is received, renew the access token and retry the request
+      if (response.getStatusInfo() == Status.UNAUTHORIZED) {
+        for (String authName : authNames) {
+          Authentication authentication = authentications.get(authName);
+          if (authentication instanceof OAuth) {
+            OAuth2AccessToken accessToken = ((OAuth) authentication).renewAccessToken();
+            if (accessToken != null) {
+              invocationBuilder.header("Authorization", null);
+              invocationBuilder.header("Authorization", "Bearer " + accessToken.getAccessToken());
+              response = sendRequest(method, invocationBuilder, entity);
+            }
+            break;
+          }
+        }
       }
 
       int statusCode = response.getStatusInfo().getStatusCode();
       Map<String, List<String>> responseHeaders = buildResponseHeaders(response);
 
-      if (response.getStatus() == Status.NO_CONTENT.getStatusCode()) {
-        return new ApiResponse<{{#supportJava6}}T{{/supportJava6}}>(statusCode, responseHeaders);
+      if (response.getStatusInfo() == Status.NO_CONTENT) {
+        return new ApiResponse<T>(statusCode, responseHeaders);
       } else if (response.getStatusInfo().getFamily() == Status.Family.SUCCESSFUL) {
-        if (returnType == null)
-          return new ApiResponse<{{#supportJava6}}T{{/supportJava6}}>(statusCode, responseHeaders);
-        else
-          if (schema == null) {
-            return new ApiResponse<>(statusCode, responseHeaders, deserialize(response, returnType));
-          } else { // oneOf/anyOf
-            return new ApiResponse<>(statusCode, responseHeaders, (T)deserializeSchemas(response, schema));
-          }
+        if (returnType == null) return new ApiResponse<T>(statusCode, responseHeaders);
+        else if (schema == null) {
+          return new ApiResponse<T>(statusCode, responseHeaders, deserialize(response, returnType));
+        } else { // oneOf/anyOf
+          return new ApiResponse<T>(
+              statusCode, responseHeaders, (T) deserializeSchemas(response, schema));
+        }
       } else {
         String message = "error";
         String respBody = null;
@@ -1040,20 +1127,34 @@ public class ApiClient {
           }
         }
         throw new ApiException(
-          response.getStatus(),
-          message,
-          buildResponseHeaders(response),
-          respBody);
+            response.getStatus(), message, buildResponseHeaders(response), respBody);
       }
     } finally {
       try {
         response.close();
       } catch (Exception e) {
-        // it's not critical, since the response object is local in method invokeAPI; that's fine, just continue
+        // it's not critical, since the response object is local in method invokeAPI; that's fine,
+        // just continue
       }
     }
   }
 
+  private Response sendRequest(String method, Invocation.Builder invocationBuilder, Entity<?> entity) {
+    Response response;
+    if ("POST".equals(method)) {
+      response = invocationBuilder.post(entity);
+    } else if ("PUT".equals(method)) {
+      response = invocationBuilder.put(entity);
+    } else if ("DELETE".equals(method)) {
+      response = invocationBuilder.method("DELETE", entity);
+    } else if ("PATCH".equals(method)) {
+      response = invocationBuilder.method("PATCH", entity);
+    } else {
+      response = invocationBuilder.method(method);
+    }
+    return response;
+  }
+
   /**
    * @deprecated Add qualified name of the operation as a first parameter.
    */

modules/openapi-generator/src/main/resources/Java/libraries/jersey2-experimental/auth/OAuth.mustache

@@ -4,27 +4,169 @@ package {{invokerPackage}}.auth;
 
 import {{invokerPackage}}.Pair;
 import {{invokerPackage}}.ApiException;
+import com.github.scribejava.core.builder.ServiceBuilder;
+import com.github.scribejava.core.builder.api.DefaultApi20;
+import com.github.scribejava.core.exceptions.OAuthException;
+import com.github.scribejava.core.model.OAuth2AccessToken;
+import com.github.scribejava.core.oauth.OAuth20Service;
 
+import javax.ws.rs.core.UriBuilder;
+import java.io.IOException;
+import java.net.MalformedURLException;
 import java.net.URI;
-import java.util.Map;
 import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ExecutionException;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 
 {{>generatedAnnotation}}
 public class OAuth implements Authentication {
-  private String accessToken;
+  private static final Logger log = Logger.getLogger(OAuth.class.getName());
 
-  public String getAccessToken() {
-    return accessToken;
+  private String tokenUrl;
+  private String absoluteTokenUrl;
+  private OAuthFlow flow = OAuthFlow.application;
+  private OAuth20Service service;
+  private DefaultApi20 authApi;
+  private String scope;
+  private String username;
+  private String password;
+  private String code;
+  private volatile OAuth2AccessToken accessToken;
+
+  public OAuth(String basePath, String tokenUrl) {
+    this.tokenUrl = tokenUrl;
+    this.absoluteTokenUrl = createAbsoluteTokenUrl(basePath, tokenUrl);
+    authApi = new DefaultApi20() {
+      @Override
+      public String getAccessTokenEndpoint() {
+        return absoluteTokenUrl;
+      }
+
+      @Override
+      protected String getAuthorizationBaseUrl() {
+        throw new UnsupportedOperationException("Shouldn't get there !");
+      }
+    };
   }
 
-  public void setAccessToken(String accessToken) {
-    this.accessToken = accessToken;
+  private static String createAbsoluteTokenUrl(String basePath, String tokenUrl) {
+    if (!URI.create(tokenUrl).isAbsolute()) {
+      try {
+        return UriBuilder.fromPath(basePath).path(tokenUrl).build().toURL().toString();
+      } catch (MalformedURLException e) {
+        log.log(Level.SEVERE, "Couldn't create absolute token URL", e);
+      }
+    }
+    return tokenUrl;
   }
 
   @Override
-  public void applyToParams(List<Pair> queryParams, Map<String, String> headerParams, Map<String, String> cookieParams, String payload, String method, URI uri) throws ApiException {
+  public void applyToParams(
+      List<Pair> queryParams,
+      Map<String, String> headerParams,
+      Map<String, String> cookieParams,
+      String payload,
+      String method,
+      URI uri)
+      throws ApiException {
+
+    if (accessToken == null) {
+      obtainAccessToken(null);
+    }
     if (accessToken != null) {
-      headerParams.put("Authorization", "Bearer " + accessToken);
+      headerParams.put("Authorization", "Bearer " + accessToken.getAccessToken());
     }
   }
+
+  public OAuth2AccessToken renewAccessToken() throws ApiException {
+    String refreshToken = null;
+    if (accessToken != null) {
+      refreshToken = accessToken.getRefreshToken();
+      accessToken = null;
+    }
+    return obtainAccessToken(refreshToken);
+  }
+
+  public synchronized OAuth2AccessToken obtainAccessToken(String refreshToken) throws ApiException {
+    if (service == null) {
+      return null;
+    }
+    try {
+      if (refreshToken != null) {
+        return service.refreshAccessToken(refreshToken);
+      }
+    } catch (OAuthException | InterruptedException | ExecutionException | IOException e) {
+      log.log(Level.FINE, "Refreshing the access token using the refresh token failed", e);
+    }
+    try {
+      switch (flow) {
+        case password:
+          if (username != null && password != null) {
+            accessToken = service.getAccessTokenPasswordGrant(username, password, scope);
+          }
+          break;
+        case accessCode:
+          if (code != null) {
+            accessToken = service.getAccessToken(code);
+            code = null;
+          }
+          break;
+        case application:
+          accessToken = service.getAccessTokenClientCredentialsGrant(scope);
+      }
+    } catch (OAuthException | InterruptedException | ExecutionException | IOException e) {
+      throw new ApiException(e);
+    }
+    return accessToken;
+  }
+
+  public OAuth2AccessToken getAccessToken() {
+    return accessToken;
+  }
+
+  public OAuth setAccessToken(OAuth2AccessToken accessToken) {
+    this.accessToken = accessToken;
+    return this;
+  }
+
+  public OAuth setAccessToken(String accessToken) {
+    this.accessToken = new OAuth2AccessToken(accessToken);
+    return this;
+  }
+
+  public OAuth setScope(String scope) {
+    this.scope = scope;
+    return this;
+  }
+
+  public OAuth setCredentials(String clientId, String clientSecret) {
+    service = new ServiceBuilder(clientId)
+        .apiSecret(clientSecret)
+        .build(authApi);
+    return this;
+  }
+
+  public OAuth usePasswordFlow(String username, String password) {
+    this.flow = OAuthFlow.password;
+    this.username = username;
+    this.password = password;
+    return this;
+  }
+
+  public OAuth useAuthorizationCodeFlow(String code) {
+    this.flow = OAuthFlow.accessCode;
+    this.code = code;
+    return this;
+  }
+
+  public OAuth setFlow(OAuthFlow flow) {
+    this.flow = flow;
+    return this;
+  }
+
+  public void setBasePath(String basePath) {
+    this.absoluteTokenUrl = createAbsoluteTokenUrl(basePath, tokenUrl);
+  }
 }

modules/openapi-generator/src/main/resources/Java/libraries/jersey2-experimental/pom.mustache

@@ -343,6 +343,13 @@
             <artifactId>tomitribe-http-signatures</artifactId>
             <version>${http-signature-version}</version>
         </dependency>
+        {{#hasOAuthMethods}}
+        <dependency>
+            <groupId>com.github.scribejava</groupId>
+            <artifactId>scribejava-apis</artifactId>
+            <version>6.9.0</version>
+        </dependency>
+        {{/hasOAuthMethods}}
         {{#useBeanValidation}}
         <!-- Bean Validation API support -->
         <dependency>

samples/client/petstore/java/feign/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/feign10x/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/google-api-client/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/jersey1/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/jersey2-experimental/pom.xml

@@ -284,6 +284,11 @@
             <artifactId>tomitribe-http-signatures</artifactId>
             <version>${http-signature-version}</version>
         </dependency>
+        <dependency>
+            <groupId>com.github.scribejava</groupId>
+            <artifactId>scribejava-apis</artifactId>
+            <version>6.9.0</version>
+        </dependency>
         <!-- test dependencies -->
         <dependency>
             <groupId>junit</groupId>

samples/client/petstore/java/jersey2-experimental/src/main/java/org/openapitools/client/ApiClient.java

@@ -11,6 +11,7 @@ import javax.ws.rs.core.MediaType;
 import javax.ws.rs.core.Response;
 import javax.ws.rs.core.Response.Status;
 
+import com.github.scribejava.core.model.OAuth2AccessToken;
 import org.glassfish.jersey.client.ClientConfig;
 import org.glassfish.jersey.client.ClientProperties;
 import org.glassfish.jersey.client.HttpUrlConnectorProvider;
@@ -37,7 +38,6 @@ import java.util.List;
 import java.util.Arrays;
 import java.util.ArrayList;
 import java.util.Date;
-import java.util.TimeZone;
 
 import java.net.URLEncoder;
 
@@ -53,9 +53,8 @@ import org.openapitools.client.auth.HttpBasicAuth;
 import org.openapitools.client.auth.HttpBearerAuth;
 import org.openapitools.client.auth.HttpSignatureAuth;
 import org.openapitools.client.auth.ApiKeyAuth;
-import org.openapitools.client.model.AbstractOpenApiSchema;
-
 import org.openapitools.client.auth.OAuth;
+import org.openapitools.client.model.AbstractOpenApiSchema;
 
 
 public class ApiClient {
@@ -168,7 +167,7 @@ public class ApiClient {
     authentications.put("bearer_test", new HttpBearerAuth("bearer"));
     authentications.put("http_basic_test", new HttpBasicAuth());
     authentications.put("http_signature_test", new HttpSignatureAuth("http_signature_test", null, null));
-    authentications.put("petstore_auth", new OAuth());
+    authentications.put("petstore_auth", new OAuth(basePath, ""));
     // Prevent the authentications from being modified.
     authentications = Collections.unmodifiableMap(authentications);
 
@@ -178,6 +177,7 @@ public class ApiClient {
 
   /**
    * Gets the JSON instance to do JSON serialization and deserialization.
+   *
    * @return JSON
    */
   public JSON getJSON() {
@@ -199,6 +199,7 @@ public class ApiClient {
 
   public ApiClient setBasePath(String basePath) {
     this.basePath = basePath;
+    setOauthBasePath(basePath);
     return this;
   }
 
@@ -208,6 +209,7 @@ public class ApiClient {
 
   public ApiClient setServers(List<ServerConfiguration> servers) {
     this.servers = servers;
+    updateBasePath();
     return this;
   }
 
@@ -217,6 +219,7 @@ public class ApiClient {
 
   public ApiClient setServerIndex(Integer serverIndex) {
     this.serverIndex = serverIndex;
+    updateBasePath();
     return this;
   }
 
@@ -226,11 +229,25 @@ public class ApiClient {
 
   public ApiClient setServerVariables(Map<String, String> serverVariables) {
     this.serverVariables = serverVariables;
+    updateBasePath();
     return this;
   }
 
+  private void updateBasePath() {
+    setBasePath(servers.get(serverIndex).URL(serverVariables));
+  }
+
+  private void setOauthBasePath(String basePath) {
+    for(Authentication auth : authentications.values()) {
+      if (auth instanceof OAuth) {
+        ((OAuth) auth).setBasePath(basePath);
+      }
+    }
+  }
+
   /**
    * Get authentications (key: authentication name, value: authentication).
+   *
    * @return Map of authentication object
    */
   public Map<String, Authentication> getAuthentications() {
@@ -249,13 +266,14 @@ public class ApiClient {
 
   /**
    * Helper method to set username for the first HTTP basic authentication.
+   *
    * @param username Username
    */
-  public void setUsername(String username) {
+  public ApiClient setUsername(String username) {
     for (Authentication auth : authentications.values()) {
       if (auth instanceof HttpBasicAuth) {
         ((HttpBasicAuth) auth).setUsername(username);
-        return;
+        return this;
       }
     }
     throw new RuntimeException("No HTTP basic authentication configured!");
@@ -263,13 +281,14 @@ public class ApiClient {
 
   /**
    * Helper method to set password for the first HTTP basic authentication.
+   *
    * @param password Password
    */
-  public void setPassword(String password) {
+  public ApiClient setPassword(String password) {
     for (Authentication auth : authentications.values()) {
       if (auth instanceof HttpBasicAuth) {
         ((HttpBasicAuth) auth).setPassword(password);
-        return;
+        return this;
       }
     }
     throw new RuntimeException("No HTTP basic authentication configured!");
@@ -277,13 +296,14 @@ public class ApiClient {
 
   /**
    * Helper method to set API key value for the first API key authentication.
+   *
    * @param apiKey API key
    */
-  public void setApiKey(String apiKey) {
+  public ApiClient setApiKey(String apiKey) {
     for (Authentication auth : authentications.values()) {
       if (auth instanceof ApiKeyAuth) {
         ((ApiKeyAuth) auth).setApiKey(apiKey);
-        return;
+        return this;
       }
     }
     throw new RuntimeException("No API key authentication configured!");
@@ -294,29 +314,31 @@ public class ApiClient {
    *
    * @param secrets Hash map from authentication name to its secret.
    */
-  public void configureApiKeys(HashMap<String, String> secrets) {
+  public ApiClient configureApiKeys(HashMap<String, String> secrets) {
     for (Map.Entry<String, Authentication> authEntry : authentications.entrySet()) {
       Authentication auth = authEntry.getValue();
       if (auth instanceof ApiKeyAuth) {
         String name = authEntry.getKey();
         // respect x-auth-id-alias property
-        name = authenticationLookup.getOrDefault(name, name);
+        name = authenticationLookup.containsKey(name) ? authenticationLookup.get(name) : name;
         if (secrets.containsKey(name)) {
           ((ApiKeyAuth) auth).setApiKey(secrets.get(name));
         }
       }
     }
+    return this;
   }
 
   /**
    * Helper method to set API key prefix for the first API key authentication.
+   *
    * @param apiKeyPrefix API key prefix
    */
-  public void setApiKeyPrefix(String apiKeyPrefix) {
+  public ApiClient setApiKeyPrefix(String apiKeyPrefix) {
     for (Authentication auth : authentications.values()) {
       if (auth instanceof ApiKeyAuth) {
         ((ApiKeyAuth) auth).setApiKeyPrefix(apiKeyPrefix);
-        return;
+        return this;
       }
     }
     throw new RuntimeException("No API key authentication configured!");
@@ -324,27 +346,91 @@ public class ApiClient {
 
   /**
    * Helper method to set bearer token for the first Bearer authentication.
+   *
    * @param bearerToken Bearer token
    */
-  public void setBearerToken(String bearerToken) {
+  public ApiClient setBearerToken(String bearerToken) {
     for (Authentication auth : authentications.values()) {
       if (auth instanceof HttpBearerAuth) {
         ((HttpBearerAuth) auth).setBearerToken(bearerToken);
-        return;
+        return this;
       }
     }
     throw new RuntimeException("No Bearer authentication configured!");
   }
 
+
   /**
    * Helper method to set access token for the first OAuth2 authentication.
    * @param accessToken Access token
    */
-  public void setAccessToken(String accessToken) {
+  public ApiClient setAccessToken(String accessToken) {
     for (Authentication auth : authentications.values()) {
       if (auth instanceof OAuth) {
         ((OAuth) auth).setAccessToken(accessToken);
-        return;
+        return this;
+      }
+    }
+    throw new RuntimeException("No OAuth2 authentication configured!");
+  }
+
+  /**
+   * Helper method to set the credentials for the first OAuth2 authentication.
+   *
+   * @param clientId the client ID
+   * @param clientSecret the client secret
+   */
+  public ApiClient setOauthCredentials(String clientId, String clientSecret) {
+    for (Authentication auth : authentications.values()) {
+      if (auth instanceof OAuth) {
+        ((OAuth) auth).setCredentials(clientId, clientSecret);
+        return this;
+      }
+    }
+    throw new RuntimeException("No OAuth2 authentication configured!");
+  }
+
+  /**
+   * Helper method to set the password flow for the first OAuth2 authentication.
+   *
+   * @param username the user name
+   * @param password the user password
+   */
+  public ApiClient setOauthPasswordFlow(String username, String password) {
+    for (Authentication auth : authentications.values()) {
+      if (auth instanceof OAuth) {
+        ((OAuth) auth).usePasswordFlow(username, password);
+        return this;
+      }
+    }
+    throw new RuntimeException("No OAuth2 authentication configured!");
+  }
+
+  /**
+   * Helper method to set the authorization code flow for the first OAuth2 authentication.
+   *
+   * @param code the authorization code
+   */
+  public ApiClient setOauthAuthorizationCodeFlow(String code) {
+    for (Authentication auth : authentications.values()) {
+      if (auth instanceof OAuth) {
+        ((OAuth) auth).useAuthorizationCodeFlow(code);
+        return this;
+      }
+    }
+    throw new RuntimeException("No OAuth2 authentication configured!");
+  }
+
+  /**
+   * Helper method to set the scopes for the first OAuth2 authentication.
+   *
+   * @param scope the oauth scope
+   */
+  public ApiClient setOauthScope(String scope) {
+    for (Authentication auth : authentications.values()) {
+      if (auth instanceof OAuth) {
+        ((OAuth) auth).setScope(scope);
+        return this;
       }
     }
     throw new RuntimeException("No OAuth2 authentication configured!");
@@ -772,9 +858,9 @@ public class ApiClient {
     }
 
     if (matchCounter > 1 && "oneOf".equals(schema.getSchemaType())) {// more than 1 match for oneOf
-      throw new ApiException("Response body is invalid as it matches more than one schema (" + String.join(", ", matchSchemas) + ") defined in the oneOf model: " + schema.getClass().getName());
+      throw new ApiException("Response body is invalid as it matches more than one schema (" + StringUtil.join(matchSchemas, ", ") + ") defined in the oneOf model: " + schema.getClass().getName());
     } else if (matchCounter == 0) { // fail to match any in oneOf/anyOf schemas
-      throw new ApiException("Response body is invalid as it doens't match any schemas (" + String.join(", ", schema.getSchemas().keySet()) + ") defined in the oneOf/anyOf model: " + schema.getClass().getName());
+      throw new ApiException("Response body is invalid as it doens't match any schemas (" + StringUtil.join(schema.getSchemas().keySet(), ", ") + ") defined in the oneOf/anyOf model: " + schema.getClass().getName());
     } else { // only one matched
       schema.setActualInstance(result);
       return schema;
@@ -889,29 +975,35 @@ public class ApiClient {
    * @return The response body in type of string
    * @throws ApiException API exception
    */
-  public <T> ApiResponse<T> invokeAPI(String operation, String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, String> cookieParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames, GenericType<T> returnType, AbstractOpenApiSchema schema) throws ApiException {
+  public <T> ApiResponse<T> invokeAPI(
+      String operation,
+      String path,
+      String method,
+      List<Pair> queryParams,
+      Object body,
+      Map<String, String> headerParams,
+      Map<String, String> cookieParams,
+      Map<String, Object> formParams,
+      String accept,
+      String contentType,
+      String[] authNames,
+      GenericType<T> returnType,
+      AbstractOpenApiSchema schema)
+      throws ApiException {
 
     // Not using `.target(targetURL).path(path)` below,
     // to support (constant) query string in `path`, e.g. "/posts?draft=1"
     String targetURL;
-    if (serverIndex != null) {
-      Integer index;
-      List<ServerConfiguration> serverConfigurations;
-      Map<String, String> variables;
-
-      if (operationServers.containsKey(operation)) {
-        index = operationServerIndex.getOrDefault(operation, serverIndex);
-        variables = operationServerVariables.getOrDefault(operation, serverVariables);
-        serverConfigurations = operationServers.get(operation);
-      } else {
-        index = serverIndex;
-        variables = serverVariables;
-        serverConfigurations = servers;
-      }
+    if (operationServers.containsKey(operation)) {
+      Integer index = operationServerIndex.containsKey(operation) ? operationServerIndex.get(operation) : serverIndex;
+      Map<String, String> variables = operationServerVariables.containsKey(operation) ?
+        operationServerVariables.get(operation) : serverVariables;
+      List<ServerConfiguration> serverConfigurations = operationServers.get(operation);
       if (index < 0 || index >= serverConfigurations.size()) {
-        throw new ArrayIndexOutOfBoundsException(String.format(
-          "Invalid index %d when selecting the host settings. Must be less than %d", index, serverConfigurations.size()
-        ));
+        throw new ArrayIndexOutOfBoundsException(
+            String.format(
+                "Invalid index %d when selecting the host settings. Must be less than %d",
+                index, serverConfigurations.size()));
       }
       targetURL = serverConfigurations.get(index).URL(variables) + path;
     } else {
@@ -929,13 +1021,6 @@ public class ApiClient {
 
     Invocation.Builder invocationBuilder = target.request().accept(accept);
 
-    for (Entry<String, String> entry : headerParams.entrySet()) {
-      String value = entry.getValue();
-      if (value != null) {
-        invocationBuilder = invocationBuilder.header(entry.getKey(), value);
-      }
-    }
-
     for (Entry<String, String> entry : cookieParams.entrySet()) {
       String value = entry.getValue();
       if (value != null) {
@@ -950,63 +1035,63 @@ public class ApiClient {
       }
     }
 
-    for (Entry<String, String> entry : defaultHeaderMap.entrySet()) {
-      String key = entry.getKey();
-      if (!headerParams.containsKey(key)) {
-        String value = entry.getValue();
-        if (value != null) {
-          invocationBuilder = invocationBuilder.header(key, value);
-        }
-      }
-    }
-
     Entity<?> entity = serialize(body, formParams, contentType);
 
     // put all headers in one place
-    Map<String, String> allHeaderParams = new HashMap<>();
-    allHeaderParams.putAll(defaultHeaderMap);
+    Map<String, String> allHeaderParams = new HashMap<>(defaultHeaderMap);
     allHeaderParams.putAll(headerParams);
-   
+
     // update different parameters (e.g. headers) for authentication
-    updateParamsForAuth(authNames, queryParams, allHeaderParams, cookieParams, serializeToString(body, formParams, contentType), method, target.getUri());
+    updateParamsForAuth(
+        authNames,
+        queryParams,
+        allHeaderParams,
+        cookieParams,
+        serializeToString(body, formParams, contentType),
+        method,
+        target.getUri());
+
+    for (Entry<String, String> entry : allHeaderParams.entrySet()) {
+      String value = entry.getValue();
+      if (value != null) {
+        invocationBuilder = invocationBuilder.header(entry.getKey(), value);
+      }
+    }
 
     Response response = null;
 
     try {
-      if ("GET".equals(method)) {
-        response = invocationBuilder.get();
-      } else if ("POST".equals(method)) {
-        response = invocationBuilder.post(entity);
-      } else if ("PUT".equals(method)) {
-        response = invocationBuilder.put(entity);
-      } else if ("DELETE".equals(method)) {
-        response = invocationBuilder.method("DELETE", entity);
-      } else if ("PATCH".equals(method)) {
-        response = invocationBuilder.method("PATCH", entity);
-      } else if ("HEAD".equals(method)) {
-        response = invocationBuilder.head();
-      } else if ("OPTIONS".equals(method)) {
-        response = invocationBuilder.options();
-      } else if ("TRACE".equals(method)) {
-        response = invocationBuilder.trace();
-      } else {
-        throw new ApiException(500, "unknown method type " + method);
+      response = sendRequest(method, invocationBuilder, entity);
+
+      // If OAuth is used and a status 401 is received, renew the access token and retry the request
+      if (response.getStatusInfo() == Status.UNAUTHORIZED) {
+        for (String authName : authNames) {
+          Authentication authentication = authentications.get(authName);
+          if (authentication instanceof OAuth) {
+            OAuth2AccessToken accessToken = ((OAuth) authentication).renewAccessToken();
+            if (accessToken != null) {
+              invocationBuilder.header("Authorization", null);
+              invocationBuilder.header("Authorization", "Bearer " + accessToken.getAccessToken());
+              response = sendRequest(method, invocationBuilder, entity);
+            }
+            break;
+          }
+        }
       }
 
       int statusCode = response.getStatusInfo().getStatusCode();
       Map<String, List<String>> responseHeaders = buildResponseHeaders(response);
 
-      if (response.getStatus() == Status.NO_CONTENT.getStatusCode()) {
-        return new ApiResponse<>(statusCode, responseHeaders);
+      if (response.getStatusInfo() == Status.NO_CONTENT) {
+        return new ApiResponse<T>(statusCode, responseHeaders);
       } else if (response.getStatusInfo().getFamily() == Status.Family.SUCCESSFUL) {
-        if (returnType == null)
-          return new ApiResponse<>(statusCode, responseHeaders);
-        else
-          if (schema == null) {
-            return new ApiResponse<>(statusCode, responseHeaders, deserialize(response, returnType));
-          } else { // oneOf/anyOf
-            return new ApiResponse<>(statusCode, responseHeaders, (T)deserializeSchemas(response, schema));
-          }
+        if (returnType == null) return new ApiResponse<T>(statusCode, responseHeaders);
+        else if (schema == null) {
+          return new ApiResponse<T>(statusCode, responseHeaders, deserialize(response, returnType));
+        } else { // oneOf/anyOf
+          return new ApiResponse<T>(
+              statusCode, responseHeaders, (T) deserializeSchemas(response, schema));
+        }
       } else {
         String message = "error";
         String respBody = null;
@@ -1019,20 +1104,34 @@ public class ApiClient {
           }
         }
         throw new ApiException(
-          response.getStatus(),
-          message,
-          buildResponseHeaders(response),
-          respBody);
+            response.getStatus(), message, buildResponseHeaders(response), respBody);
       }
     } finally {
       try {
         response.close();
       } catch (Exception e) {
-        // it's not critical, since the response object is local in method invokeAPI; that's fine, just continue
+        // it's not critical, since the response object is local in method invokeAPI; that's fine,
+        // just continue
       }
     }
   }
 
+  private Response sendRequest(String method, Invocation.Builder invocationBuilder, Entity<?> entity) {
+    Response response;
+    if ("POST".equals(method)) {
+      response = invocationBuilder.post(entity);
+    } else if ("PUT".equals(method)) {
+      response = invocationBuilder.put(entity);
+    } else if ("DELETE".equals(method)) {
+      response = invocationBuilder.method("DELETE", entity);
+    } else if ("PATCH".equals(method)) {
+      response = invocationBuilder.method("PATCH", entity);
+    } else {
+      response = invocationBuilder.method(method);
+    }
+    return response;
+  }
+
   /**
    * @deprecated Add qualified name of the operation as a first parameter.
    */

samples/client/petstore/java/jersey2-experimental/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/jersey2-experimental/src/main/java/org/openapitools/client/auth/OAuth.java

@@ -15,27 +15,169 @@ package org.openapitools.client.auth;
 
 import org.openapitools.client.Pair;
 import org.openapitools.client.ApiException;
+import com.github.scribejava.core.builder.ServiceBuilder;
+import com.github.scribejava.core.builder.api.DefaultApi20;
+import com.github.scribejava.core.exceptions.OAuthException;
+import com.github.scribejava.core.model.OAuth2AccessToken;
+import com.github.scribejava.core.oauth.OAuth20Service;
 
+import javax.ws.rs.core.UriBuilder;
+import java.io.IOException;
+import java.net.MalformedURLException;
 import java.net.URI;
-import java.util.Map;
 import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ExecutionException;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 
 
 public class OAuth implements Authentication {
-  private String accessToken;
+  private static final Logger log = Logger.getLogger(OAuth.class.getName());
 
-  public String getAccessToken() {
-    return accessToken;
+  private String tokenUrl;
+  private String absoluteTokenUrl;
+  private OAuthFlow flow = OAuthFlow.application;
+  private OAuth20Service service;
+  private DefaultApi20 authApi;
+  private String scope;
+  private String username;
+  private String password;
+  private String code;
+  private volatile OAuth2AccessToken accessToken;
+
+  public OAuth(String basePath, String tokenUrl) {
+    this.tokenUrl = tokenUrl;
+    this.absoluteTokenUrl = createAbsoluteTokenUrl(basePath, tokenUrl);
+    authApi = new DefaultApi20() {
+      @Override
+      public String getAccessTokenEndpoint() {
+        return absoluteTokenUrl;
+      }
+
+      @Override
+      protected String getAuthorizationBaseUrl() {
+        throw new UnsupportedOperationException("Shouldn't get there !");
+      }
+    };
   }
 
-  public void setAccessToken(String accessToken) {
-    this.accessToken = accessToken;
+  private static String createAbsoluteTokenUrl(String basePath, String tokenUrl) {
+    if (!URI.create(tokenUrl).isAbsolute()) {
+      try {
+        return UriBuilder.fromPath(basePath).path(tokenUrl).build().toURL().toString();
+      } catch (MalformedURLException e) {
+        log.log(Level.SEVERE, "Couldn't create absolute token URL", e);
+      }
+    }
+    return tokenUrl;
   }
 
   @Override
-  public void applyToParams(List<Pair> queryParams, Map<String, String> headerParams, Map<String, String> cookieParams, String payload, String method, URI uri) throws ApiException {
+  public void applyToParams(
+      List<Pair> queryParams,
+      Map<String, String> headerParams,
+      Map<String, String> cookieParams,
+      String payload,
+      String method,
+      URI uri)
+      throws ApiException {
+
+    if (accessToken == null) {
+      obtainAccessToken(null);
+    }
     if (accessToken != null) {
-      headerParams.put("Authorization", "Bearer " + accessToken);
+      headerParams.put("Authorization", "Bearer " + accessToken.getAccessToken());
     }
   }
+
+  public OAuth2AccessToken renewAccessToken() throws ApiException {
+    String refreshToken = null;
+    if (accessToken != null) {
+      refreshToken = accessToken.getRefreshToken();
+      accessToken = null;
+    }
+    return obtainAccessToken(refreshToken);
+  }
+
+  public synchronized OAuth2AccessToken obtainAccessToken(String refreshToken) throws ApiException {
+    if (service == null) {
+      return null;
+    }
+    try {
+      if (refreshToken != null) {
+        return service.refreshAccessToken(refreshToken);
+      }
+    } catch (OAuthException | InterruptedException | ExecutionException | IOException e) {
+      log.log(Level.FINE, "Refreshing the access token using the refresh token failed", e);
+    }
+    try {
+      switch (flow) {
+        case password:
+          if (username != null && password != null) {
+            accessToken = service.getAccessTokenPasswordGrant(username, password, scope);
+          }
+          break;
+        case accessCode:
+          if (code != null) {
+            accessToken = service.getAccessToken(code);
+            code = null;
+          }
+          break;
+        case application:
+          accessToken = service.getAccessTokenClientCredentialsGrant(scope);
+      }
+    } catch (OAuthException | InterruptedException | ExecutionException | IOException e) {
+      throw new ApiException(e);
+    }
+    return accessToken;
+  }
+
+  public OAuth2AccessToken getAccessToken() {
+    return accessToken;
+  }
+
+  public OAuth setAccessToken(OAuth2AccessToken accessToken) {
+    this.accessToken = accessToken;
+    return this;
+  }
+
+  public OAuth setAccessToken(String accessToken) {
+    this.accessToken = new OAuth2AccessToken(accessToken);
+    return this;
+  }
+
+  public OAuth setScope(String scope) {
+    this.scope = scope;
+    return this;
+  }
+
+  public OAuth setCredentials(String clientId, String clientSecret) {
+    service = new ServiceBuilder(clientId)
+        .apiSecret(clientSecret)
+        .build(authApi);
+    return this;
+  }
+
+  public OAuth usePasswordFlow(String username, String password) {
+    this.flow = OAuthFlow.password;
+    this.username = username;
+    this.password = password;
+    return this;
+  }
+
+  public OAuth useAuthorizationCodeFlow(String code) {
+    this.flow = OAuthFlow.accessCode;
+    this.code = code;
+    return this;
+  }
+
+  public OAuth setFlow(OAuthFlow flow) {
+    this.flow = flow;
+    return this;
+  }
+
+  public void setBasePath(String basePath) {
+    this.absoluteTokenUrl = createAbsoluteTokenUrl(basePath, tokenUrl);
+  }
 }

samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/jersey2-java8/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/jersey2/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/okhttp-gson/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/resteasy/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/retrofit/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/retrofit2-play24/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/retrofit2-play25/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/retrofit2-play26/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/retrofit2/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/retrofit2rx/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/retrofit2rx2/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/vertx/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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/webclient/src/main/java/org/openapitools/client/StringUtil.java

@@ -13,6 +13,9 @@
 
 package org.openapitools.client;
 
+import java.util.Collection;
+import java.util.Iterator;
+
 
 public class StringUtil {
   /**
@@ -58,4 +61,23 @@ public class StringUtil {
     }
     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();
+  }
 }