use okttp builder instead of instance in retrofit2

Fix #3188

modules/swagger-codegen/src/main/resources/Java/libraries/retrofit2/ApiClient.mustache

@@ -48,7 +48,7 @@ import {{invokerPackage}}.auth.OAuthFlow;
 public class ApiClient {
 
     private Map<String, Interceptor> apiAuthorizations;
-    private OkHttpClient okClient;
+    private OkHttpClient.Builder okBuilder;
     private Retrofit.Builder adapterBuilder;
 
     public ApiClient() {
@@ -118,7 +118,7 @@ public class ApiClient {
                 .setPassword(password);
     }
 
-   public void createDefaultAdapter() {
+    public void createDefaultAdapter() {
         Gson gson = new GsonBuilder()
                 .setDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ")
                 {{^java8}}
@@ -130,7 +130,7 @@ public class ApiClient {
                 .registerTypeAdapter(LocalDate.class, new LocalDateTypeAdapter())
                 .create();
 
-        okClient = new OkHttpClient();
+        okBuilder = new OkHttpClient.Builder();
 
         String baseUrl = "{{{basePath}}}";
         if(!baseUrl.endsWith("/"))
@@ -139,14 +139,16 @@ public class ApiClient {
         adapterBuilder = new Retrofit
                 .Builder()
                 .baseUrl(baseUrl)
-                .client(okClient)
                 {{#useRxJava}}.addCallAdapterFactory(RxJavaCallAdapterFactory.create()){{/useRxJava}}
                 .addConverterFactory(ScalarsConverterFactory.create())
                 .addConverterFactory(GsonCustomConverterFactory.create(gson));
     }
 
     public <S> S createService(Class<S> serviceClass) {
-        return adapterBuilder.build().create(serviceClass);
+        return adapterBuilder
+            .client(okBuilder.build())
+            .build()
+            .create(serviceClass);
 
     }
 
@@ -272,7 +274,7 @@ public class ApiClient {
             throw new RuntimeException("auth name \"" + authName + "\" already in api authorizations");
         }
         apiAuthorizations.put(authName, authorization);
-        okClient.interceptors().add(authorization);
+        okBuilder.addInterceptor(authorization);
     }
 
     public Map<String, Interceptor> getApiAuthorizations() {
@@ -291,24 +293,24 @@ public class ApiClient {
         this.adapterBuilder = adapterBuilder;
     }
 
-    public OkHttpClient getOkClient() {
-        return okClient;
+    public OkHttpClient.Builder getOkBuilder() {
+        return okBuilder;
     }
 
-    public void addAuthsToOkClient(OkHttpClient okClient) {
+    public void addAuthsToOkBuilder(OkHttpClient.Builder okBuilder) {
         for(Interceptor apiAuthorization : apiAuthorizations.values()) {
-            okClient.interceptors().add(apiAuthorization);
+            okBuilder.addInterceptor(apiAuthorization);
         }
     }
 
     /**
-     * Clones the okClient given in parameter, adds the auth interceptors and uses it to configure the Retrofit
+     * Clones the okBuilder given in parameter, adds the auth interceptors and uses it to configure the Retrofit
      * @param okClient
      */
     public void configureFromOkclient(OkHttpClient okClient) {
-        OkHttpClient clone = okClient.newBuilder().build();
-        addAuthsToOkClient(clone);
-        adapterBuilder.client(clone);
+        this.okBuilder = okClient.newBuilder();
+        addAuthsToOkBuilder(this.okBuilder);
+
     }
 }
 

modules/swagger-codegen/src/main/resources/Java/libraries/retrofit2/README.mustache

@@ -32,10 +32,6 @@ After the client library is installed/deployed, you can use it in your Maven pro
 
 ```
 
-## Recommendation
-
-It's recommended to create an instance of `ApiClient` per thread in a multithreaded environment to avoid any potential issue.
-
 ## Author
 
 {{#apiInfo}}{{#apis}}{{^hasMore}}{{infoEmail}}

modules/swagger-codegen/src/main/resources/Java/libraries/retrofit2/pom.mustache

@@ -155,16 +155,15 @@
     <java.version>{{#java8}}1.8{{/java8}}{{^java8}}1.7{{/java8}}</java.version>
     <maven.compiler.source>${java.version}</maven.compiler.source>
     <maven.compiler.target>${java.version}</maven.compiler.target>
-    <swagger-core-version>1.5.8</swagger-core-version>
-    <retrofit-version>2.0.2</retrofit-version>
+    <swagger-core-version>1.5.9</swagger-core-version>
+    <retrofit-version>2.1.0</retrofit-version>
     {{#useRxJava}}
-    <rxjava-version>1.1.3</rxjava-version>
+    <rxjava-version>1.1.6</rxjava-version>
     {{/useRxJava}}
     {{^java8}}
-    <jodatime-version>2.9.3</jodatime-version>
+    <jodatime-version>2.9.4</jodatime-version>
     {{/java8}}
     <oltu-version>1.0.1</oltu-version>
-    <maven-plugin-version>1.0.0</maven-plugin-version>
     <junit-version>4.12</junit-version>
   </properties>
 </project>