[Java][Client] Fix #12556 Support primitives and arrays in oneOf (#13897)

* [Java][Client] Fix #12556 Support primitives and arrays in oneOf

* Regenerate petstore samples

* Regenerate petstore test samples

* Treat 'BigDecimal' as primtive datatype

* Fix integration tests

samples/client/petstore/java/okhttp-gson/.openapi-generator/FILES

@@ -75,6 +75,7 @@ docs/Pig.md
 docs/Quadrilateral.md
 docs/QuadrilateralInterface.md
 docs/ReadOnlyFirst.md
+docs/Scalar.md
 docs/ScaleneTriangle.md
 docs/Shape.md
 docs/ShapeInterface.md
@@ -87,6 +88,9 @@ docs/Triangle.md
 docs/TriangleInterface.md
 docs/User.md
 docs/UserApi.md
+docs/Value.md
+docs/ValuesApi.md
+docs/Variable.md
 docs/Whale.md
 docs/Zebra.md
 git_push.sh
@@ -118,6 +122,7 @@ src/main/java/org/openapitools/client/api/FakeClassnameTags123Api.java
 src/main/java/org/openapitools/client/api/PetApi.java
 src/main/java/org/openapitools/client/api/StoreApi.java
 src/main/java/org/openapitools/client/api/UserApi.java
+src/main/java/org/openapitools/client/api/ValuesApi.java
 src/main/java/org/openapitools/client/auth/ApiKeyAuth.java
 src/main/java/org/openapitools/client/auth/Authentication.java
 src/main/java/org/openapitools/client/auth/HttpBasicAuth.java
@@ -192,6 +197,7 @@ src/main/java/org/openapitools/client/model/Pig.java
 src/main/java/org/openapitools/client/model/Quadrilateral.java
 src/main/java/org/openapitools/client/model/QuadrilateralInterface.java
 src/main/java/org/openapitools/client/model/ReadOnlyFirst.java
+src/main/java/org/openapitools/client/model/Scalar.java
 src/main/java/org/openapitools/client/model/ScaleneTriangle.java
 src/main/java/org/openapitools/client/model/Shape.java
 src/main/java/org/openapitools/client/model/ShapeInterface.java
@@ -202,5 +208,7 @@ src/main/java/org/openapitools/client/model/Tag.java
 src/main/java/org/openapitools/client/model/Triangle.java
 src/main/java/org/openapitools/client/model/TriangleInterface.java
 src/main/java/org/openapitools/client/model/User.java
+src/main/java/org/openapitools/client/model/Value.java
+src/main/java/org/openapitools/client/model/Variable.java
 src/main/java/org/openapitools/client/model/Whale.java
 src/main/java/org/openapitools/client/model/Zebra.java

samples/client/petstore/java/okhttp-gson/README.md

@@ -152,6 +152,7 @@ Class | Method | HTTP request | Description
 *UserApi* | [**loginUser**](docs/UserApi.md#loginUser) | **GET** /user/login | Logs user into the system
 *UserApi* | [**logoutUser**](docs/UserApi.md#logoutUser) | **GET** /user/logout | Logs out current logged in user session
 *UserApi* | [**updateUser**](docs/UserApi.md#updateUser) | **PUT** /user/{username} | Updated user
+*ValuesApi* | [**getSomeValues**](docs/ValuesApi.md#getSomeValues) | **GET** /values | Get some primitive variable values
 
 
 ## Documentation for Models
@@ -221,6 +222,7 @@ Class | Method | HTTP request | Description
  - [Quadrilateral](docs/Quadrilateral.md)
  - [QuadrilateralInterface](docs/QuadrilateralInterface.md)
  - [ReadOnlyFirst](docs/ReadOnlyFirst.md)
+ - [Scalar](docs/Scalar.md)
  - [ScaleneTriangle](docs/ScaleneTriangle.md)
  - [Shape](docs/Shape.md)
  - [ShapeInterface](docs/ShapeInterface.md)
@@ -231,6 +233,8 @@ Class | Method | HTTP request | Description
  - [Triangle](docs/Triangle.md)
  - [TriangleInterface](docs/TriangleInterface.md)
  - [User](docs/User.md)
+ - [Value](docs/Value.md)
+ - [Variable](docs/Variable.md)
  - [Whale](docs/Whale.md)
  - [Zebra](docs/Zebra.md)
 

samples/client/petstore/java/okhttp-gson/api/openapi.yaml

@@ -1132,6 +1132,23 @@ paths:
       tags:
       - fake
       x-accepts: application/json
+  /values:
+    get:
+      description: ""
+      operationId: getSomeValues
+      responses:
+        "200":
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Variable'
+          description: successful operation
+        "400":
+          description: Invalid Value
+      summary: Get some primitive variable values
+      tags:
+      - values
+      x-accepts: application/json
 components:
   requestBodies:
     UserArray:
@@ -2217,6 +2234,37 @@ components:
           items:
             type: string
           type: array
+    Variable:
+      description: Value object
+      example:
+        name: variable_1
+        value: null
+      properties:
+        name:
+          example: variable_1
+          type: string
+        value:
+          $ref: '#/components/schemas/Value'
+      required:
+      - name
+      - value
+    Value:
+      oneOf:
+      - $ref: '#/components/schemas/Scalar'
+      - $ref: '#/components/schemas/Array'
+    Scalar:
+      description: Values of scalar type
+      oneOf:
+      - maxLength: 1089
+        type: string
+      - type: number
+      - type: boolean
+    Array:
+      description: Values of array type
+      items:
+        $ref: '#/components/schemas/Scalar'
+      minItems: 1
+      type: array
     _foo_get_default_response:
       example:
         string:

samples/client/petstore/java/okhttp-gson/docs/FakeApi.md

@@ -247,7 +247,7 @@ public class Example {
 
 ### Return type
 
-[**BigDecimal**](BigDecimal.md)
+**BigDecimal**
 
 ### Authorization
 

samples/client/petstore/java/okhttp-gson/docs/Scalar.md

@@ -0,0 +1,13 @@
+
+
+# Scalar
+
+Values of scalar type
+
+## Properties
+
+| Name | Type | Description | Notes |
+|------------ | ------------- | ------------- | -------------|
+
+
+

samples/client/petstore/java/okhttp-gson/docs/Value.md

@@ -0,0 +1,12 @@
+
+
+# Value
+
+
+## Properties
+
+| Name | Type | Description | Notes |
+|------------ | ------------- | ------------- | -------------|
+
+
+

samples/client/petstore/java/okhttp-gson/docs/ValuesApi.md

@@ -0,0 +1,68 @@
+# ValuesApi
+
+All URIs are relative to *http://petstore.swagger.io:80/v2*
+
+| Method | HTTP request | Description |
+|------------- | ------------- | -------------|
+| [**getSomeValues**](ValuesApi.md#getSomeValues) | **GET** /values | Get some primitive variable values |
+
+
+<a id="getSomeValues"></a>
+# **getSomeValues**
+> Variable getSomeValues()
+
+Get some primitive variable values
+
+
+
+### Example
+```java
+// Import classes:
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.ApiException;
+import org.openapitools.client.Configuration;
+import org.openapitools.client.models.*;
+import org.openapitools.client.api.ValuesApi;
+
+public class Example {
+  public static void main(String[] args) {
+    ApiClient defaultClient = Configuration.getDefaultApiClient();
+    defaultClient.setBasePath("http://petstore.swagger.io:80/v2");
+
+    ValuesApi apiInstance = new ValuesApi(defaultClient);
+    try {
+      Variable result = apiInstance.getSomeValues();
+      System.out.println(result);
+    } catch (ApiException e) {
+      System.err.println("Exception when calling ValuesApi#getSomeValues");
+      System.err.println("Status code: " + e.getCode());
+      System.err.println("Reason: " + e.getResponseBody());
+      System.err.println("Response headers: " + e.getResponseHeaders());
+      e.printStackTrace();
+    }
+  }
+}
+```
+
+### Parameters
+This endpoint does not need any parameter.
+
+### Return type
+
+[**Variable**](Variable.md)
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+ - **Content-Type**: Not defined
+ - **Accept**: application/json
+
+### HTTP response details
+| Status code | Description | Response headers |
+|-------------|-------------|------------------|
+| **200** | successful operation |  -  |
+| **400** | Invalid Value |  -  |
+

samples/client/petstore/java/okhttp-gson/docs/Variable.md

@@ -0,0 +1,15 @@
+
+
+# Variable
+
+Value object
+
+## Properties
+
+| Name | Type | Description | Notes |
+|------------ | ------------- | ------------- | -------------|
+|**name** | **String** |  |  |
+|**value** | [**Value**](Value.md) |  |  |
+
+
+

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/JSON.java

@@ -287,6 +287,7 @@ public class JSON {
         gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.Quadrilateral.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.QuadrilateralInterface.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.ReadOnlyFirst.CustomTypeAdapterFactory());
+        gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.Scalar.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.ScaleneTriangle.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.Shape.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.ShapeInterface.CustomTypeAdapterFactory());
@@ -297,6 +298,8 @@ public class JSON {
         gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.Triangle.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.TriangleInterface.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.User.CustomTypeAdapterFactory());
+        gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.Value.CustomTypeAdapterFactory());
+        gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.Variable.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.Whale.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.Zebra.CustomTypeAdapterFactory());
         gson = gsonBuilder.create();

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/api/ValuesApi.java

@@ -0,0 +1,192 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiCallback;
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.ApiException;
+import org.openapitools.client.ApiResponse;
+import org.openapitools.client.Configuration;
+import org.openapitools.client.Pair;
+import org.openapitools.client.ProgressRequestBody;
+import org.openapitools.client.ProgressResponseBody;
+
+import com.google.gson.reflect.TypeToken;
+
+import java.io.IOException;
+
+
+import org.openapitools.client.model.Variable;
+
+import java.lang.reflect.Type;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class ValuesApi {
+    private ApiClient localVarApiClient;
+    private int localHostIndex;
+    private String localCustomBaseUrl;
+
+    public ValuesApi() {
+        this(Configuration.getDefaultApiClient());
+    }
+
+    public ValuesApi(ApiClient apiClient) {
+        this.localVarApiClient = apiClient;
+    }
+
+    public ApiClient getApiClient() {
+        return localVarApiClient;
+    }
+
+    public void setApiClient(ApiClient apiClient) {
+        this.localVarApiClient = apiClient;
+    }
+
+    public int getHostIndex() {
+        return localHostIndex;
+    }
+
+    public void setHostIndex(int hostIndex) {
+        this.localHostIndex = hostIndex;
+    }
+
+    public String getCustomBaseUrl() {
+        return localCustomBaseUrl;
+    }
+
+    public void setCustomBaseUrl(String customBaseUrl) {
+        this.localCustomBaseUrl = customBaseUrl;
+    }
+
+    /**
+     * Build call for getSomeValues
+     * @param _callback Callback for upload/download progress
+     * @return Call to execute
+     * @throws ApiException If fail to serialize the request body object
+     * @http.response.details
+     <table summary="Response Details" border="1">
+        <tr><td> Status Code </td><td> Description </td><td> Response Headers </td></tr>
+        <tr><td> 200 </td><td> successful operation </td><td>  -  </td></tr>
+        <tr><td> 400 </td><td> Invalid Value </td><td>  -  </td></tr>
+     </table>
+     */
+    public okhttp3.Call getSomeValuesCall(final ApiCallback _callback) throws ApiException {
+        String basePath = null;
+        // Operation Servers
+        String[] localBasePaths = new String[] {  };
+
+        // Determine Base Path to Use
+        if (localCustomBaseUrl != null){
+            basePath = localCustomBaseUrl;
+        } else if ( localBasePaths.length > 0 ) {
+            basePath = localBasePaths[localHostIndex];
+        } else {
+            basePath = null;
+        }
+
+        Object localVarPostBody = null;
+
+        // create path and map variables
+        String localVarPath = "/values";
+
+        List<Pair> localVarQueryParams = new ArrayList<Pair>();
+        List<Pair> localVarCollectionQueryParams = new ArrayList<Pair>();
+        Map<String, String> localVarHeaderParams = new HashMap<String, String>();
+        Map<String, String> localVarCookieParams = new HashMap<String, String>();
+        Map<String, Object> localVarFormParams = new HashMap<String, Object>();
+
+        final String[] localVarAccepts = {
+            "application/json"
+        };
+        final String localVarAccept = localVarApiClient.selectHeaderAccept(localVarAccepts);
+        if (localVarAccept != null) {
+            localVarHeaderParams.put("Accept", localVarAccept);
+        }
+
+        final String[] localVarContentTypes = {
+        };
+        final String localVarContentType = localVarApiClient.selectHeaderContentType(localVarContentTypes);
+        if (localVarContentType != null) {
+            localVarHeaderParams.put("Content-Type", localVarContentType);
+        }
+
+        String[] localVarAuthNames = new String[] {  };
+        return localVarApiClient.buildCall(basePath, localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAuthNames, _callback);
+    }
+
+    @SuppressWarnings("rawtypes")
+    private okhttp3.Call getSomeValuesValidateBeforeCall(final ApiCallback _callback) throws ApiException {
+        return getSomeValuesCall(_callback);
+
+    }
+
+    /**
+     * Get some primitive variable values
+     * 
+     * @return Variable
+     * @throws ApiException If fail to call the API, e.g. server error or cannot deserialize the response body
+     * @http.response.details
+     <table summary="Response Details" border="1">
+        <tr><td> Status Code </td><td> Description </td><td> Response Headers </td></tr>
+        <tr><td> 200 </td><td> successful operation </td><td>  -  </td></tr>
+        <tr><td> 400 </td><td> Invalid Value </td><td>  -  </td></tr>
+     </table>
+     */
+    public Variable getSomeValues() throws ApiException {
+        ApiResponse<Variable> localVarResp = getSomeValuesWithHttpInfo();
+        return localVarResp.getData();
+    }
+
+    /**
+     * Get some primitive variable values
+     * 
+     * @return ApiResponse&lt;Variable&gt;
+     * @throws ApiException If fail to call the API, e.g. server error or cannot deserialize the response body
+     * @http.response.details
+     <table summary="Response Details" border="1">
+        <tr><td> Status Code </td><td> Description </td><td> Response Headers </td></tr>
+        <tr><td> 200 </td><td> successful operation </td><td>  -  </td></tr>
+        <tr><td> 400 </td><td> Invalid Value </td><td>  -  </td></tr>
+     </table>
+     */
+    public ApiResponse<Variable> getSomeValuesWithHttpInfo() throws ApiException {
+        okhttp3.Call localVarCall = getSomeValuesValidateBeforeCall(null);
+        Type localVarReturnType = new TypeToken<Variable>(){}.getType();
+        return localVarApiClient.execute(localVarCall, localVarReturnType);
+    }
+
+    /**
+     * Get some primitive variable values (asynchronously)
+     * 
+     * @param _callback The callback to be executed when the API call finishes
+     * @return The request call
+     * @throws ApiException If fail to process the API call, e.g. serializing the request body object
+     * @http.response.details
+     <table summary="Response Details" border="1">
+        <tr><td> Status Code </td><td> Description </td><td> Response Headers </td></tr>
+        <tr><td> 200 </td><td> successful operation </td><td>  -  </td></tr>
+        <tr><td> 400 </td><td> Invalid Value </td><td>  -  </td></tr>
+     </table>
+     */
+    public okhttp3.Call getSomeValuesAsync(final ApiCallback<Variable> _callback) throws ApiException {
+
+        okhttp3.Call localVarCall = getSomeValuesValidateBeforeCall(_callback);
+        Type localVarReturnType = new TypeToken<Variable>(){}.getType();
+        localVarApiClient.executeAsync(localVarCall, localVarReturnType, _callback);
+        return localVarCall;
+    }
+}

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/AdditionalPropertiesClass.java

@@ -420,17 +420,18 @@ public class AdditionalPropertiesClass {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to AdditionalPropertiesClass
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to AdditionalPropertiesClass
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!AdditionalPropertiesClass.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!AdditionalPropertiesClass.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in AdditionalPropertiesClass is not found in the empty JSON string", AdditionalPropertiesClass.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
   }
 
   public static class CustomTypeAdapterFactory implements TypeAdapterFactory {
@@ -470,8 +471,9 @@ public class AdditionalPropertiesClass {
 
            @Override
            public AdditionalPropertiesClass read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              AdditionalPropertiesClass instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Animal.java

@@ -208,25 +208,25 @@ public class Animal {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Animal
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Animal
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!Animal.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Animal.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in Animal is not found in the empty JSON string", Animal.openapiRequiredFields.toString()));
         }
       }
 
-      String discriminatorValue = jsonObj.get("className").getAsString();
+      String discriminatorValue = jsonElement.getAsJsonObject().get("className").getAsString();
       switch (discriminatorValue) {
         case "Cat":
-          Cat.validateJsonObject(jsonObj);
+          Cat.validateJsonElement(jsonElement);
           break;
         case "Dog":
-          Dog.validateJsonObject(jsonObj);
+          Dog.validateJsonElement(jsonElement);
           break;
         default:
           throw new IllegalArgumentException(String.format("The value of the `className` field `%s` does not match any key defined in the discriminator's mapping.", discriminatorValue));

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Apple.java

@@ -206,17 +206,18 @@ public class Apple {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Apple
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Apple
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!Apple.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Apple.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in Apple is not found in the empty JSON string", Apple.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("cultivar") != null && !jsonObj.get("cultivar").isJsonNull()) && !jsonObj.get("cultivar").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `cultivar` to be a primitive type in the JSON string but got `%s`", jsonObj.get("cultivar").toString()));
       }
@@ -262,8 +263,9 @@ public class Apple {
 
            @Override
            public Apple read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              Apple instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/AppleReq.java

@@ -161,32 +161,33 @@ public class AppleReq {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to AppleReq
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to AppleReq
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!AppleReq.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!AppleReq.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in AppleReq is not found in the empty JSON string", AppleReq.openapiRequiredFields.toString()));
         }
       }
 
-      Set<Entry<String, JsonElement>> entries = jsonObj.entrySet();
+      Set<Entry<String, JsonElement>> entries = jsonElement.getAsJsonObject().entrySet();
       // check to see if the JSON string contains additional fields
       for (Entry<String, JsonElement> entry : entries) {
         if (!AppleReq.openapiFields.contains(entry.getKey())) {
-          throw new IllegalArgumentException(String.format("The field `%s` in the JSON string is not defined in the `AppleReq` properties. JSON: %s", entry.getKey(), jsonObj.toString()));
+          throw new IllegalArgumentException(String.format("The field `%s` in the JSON string is not defined in the `AppleReq` properties. JSON: %s", entry.getKey(), jsonElement.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : AppleReq.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if (!jsonObj.get("cultivar").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `cultivar` to be a primitive type in the JSON string but got `%s`", jsonObj.get("cultivar").toString()));
       }
@@ -212,9 +213,9 @@ public class AppleReq {
 
            @Override
            public AppleReq read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
-             return thisAdapter.fromJsonTree(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             return thisAdapter.fromJsonTree(jsonElement);
            }
 
        }.nullSafe();

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ArrayDefault.java

@@ -224,17 +224,18 @@ public class ArrayDefault {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ArrayDefault
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ArrayDefault
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ArrayDefault.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ArrayDefault.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ArrayDefault is not found in the empty JSON string", ArrayDefault.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       // ensure the optional json data is an array if present
       if (jsonObj.get("WithDefaultEmptyBracket") != null && !jsonObj.get("WithDefaultEmptyBracket").isJsonArray()) {
         throw new IllegalArgumentException(String.format("Expected the field `WithDefaultEmptyBracket` to be an array in the JSON string but got `%s`", jsonObj.get("WithDefaultEmptyBracket").toString()));
@@ -282,8 +283,9 @@ public class ArrayDefault {
 
            @Override
            public ArrayDefault read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ArrayDefault instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ArrayOfArrayOfNumberOnly.java

@@ -189,17 +189,18 @@ public class ArrayOfArrayOfNumberOnly {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ArrayOfArrayOfNumberOnly
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ArrayOfArrayOfNumberOnly
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ArrayOfArrayOfNumberOnly.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ArrayOfArrayOfNumberOnly.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ArrayOfArrayOfNumberOnly is not found in the empty JSON string", ArrayOfArrayOfNumberOnly.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       // ensure the optional json data is an array if present
       if (jsonObj.get("ArrayArrayNumber") != null && !jsonObj.get("ArrayArrayNumber").isJsonArray()) {
         throw new IllegalArgumentException(String.format("Expected the field `ArrayArrayNumber` to be an array in the JSON string but got `%s`", jsonObj.get("ArrayArrayNumber").toString()));
@@ -243,8 +244,9 @@ public class ArrayOfArrayOfNumberOnly {
 
            @Override
            public ArrayOfArrayOfNumberOnly read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ArrayOfArrayOfNumberOnly instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ArrayOfInlineAllOf.java

@@ -246,24 +246,25 @@ public class ArrayOfInlineAllOf {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ArrayOfInlineAllOf
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ArrayOfInlineAllOf
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ArrayOfInlineAllOf.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ArrayOfInlineAllOf.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ArrayOfInlineAllOf is not found in the empty JSON string", ArrayOfInlineAllOf.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : ArrayOfInlineAllOf.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if (!jsonObj.get("name").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `name` to be a primitive type in the JSON string but got `%s`", jsonObj.get("name").toString()));
       }
@@ -277,7 +278,7 @@ public class ArrayOfInlineAllOf {
 
           // validate the optional field `array_allof_dog_property` (array)
           for (int i = 0; i < jsonArrayarrayAllofDogProperty.size(); i++) {
-            ArrayOfInlineAllOfArrayAllofDogPropertyInner.validateJsonObject(jsonArrayarrayAllofDogProperty.get(i).getAsJsonObject());
+            ArrayOfInlineAllOfArrayAllofDogPropertyInner.validateJsonElement(jsonArrayarrayAllofDogProperty.get(i));
           };
         }
       }
@@ -320,8 +321,9 @@ public class ArrayOfInlineAllOf {
 
            @Override
            public ArrayOfInlineAllOf read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ArrayOfInlineAllOf instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ArrayOfInlineAllOfArrayAllofDogPropertyInner.java

@@ -206,17 +206,18 @@ public class ArrayOfInlineAllOfArrayAllofDogPropertyInner {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ArrayOfInlineAllOfArrayAllofDogPropertyInner
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ArrayOfInlineAllOfArrayAllofDogPropertyInner
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ArrayOfInlineAllOfArrayAllofDogPropertyInner.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ArrayOfInlineAllOfArrayAllofDogPropertyInner.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ArrayOfInlineAllOfArrayAllofDogPropertyInner is not found in the empty JSON string", ArrayOfInlineAllOfArrayAllofDogPropertyInner.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("breed") != null && !jsonObj.get("breed").isJsonNull()) && !jsonObj.get("breed").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `breed` to be a primitive type in the JSON string but got `%s`", jsonObj.get("breed").toString()));
       }
@@ -262,8 +263,9 @@ public class ArrayOfInlineAllOfArrayAllofDogPropertyInner {
 
            @Override
            public ArrayOfInlineAllOfArrayAllofDogPropertyInner read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ArrayOfInlineAllOfArrayAllofDogPropertyInner instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ArrayOfInlineAllOfArrayAllofDogPropertyInnerAllOf1.java

@@ -178,17 +178,18 @@ public class ArrayOfInlineAllOfArrayAllofDogPropertyInnerAllOf1 {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ArrayOfInlineAllOfArrayAllofDogPropertyInnerAllOf1
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ArrayOfInlineAllOfArrayAllofDogPropertyInnerAllOf1
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ArrayOfInlineAllOfArrayAllofDogPropertyInnerAllOf1.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ArrayOfInlineAllOfArrayAllofDogPropertyInnerAllOf1.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ArrayOfInlineAllOfArrayAllofDogPropertyInnerAllOf1 is not found in the empty JSON string", ArrayOfInlineAllOfArrayAllofDogPropertyInnerAllOf1.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("color") != null && !jsonObj.get("color").isJsonNull()) && !jsonObj.get("color").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `color` to be a primitive type in the JSON string but got `%s`", jsonObj.get("color").toString()));
       }
@@ -231,8 +232,9 @@ public class ArrayOfInlineAllOfArrayAllofDogPropertyInnerAllOf1 {
 
            @Override
            public ArrayOfInlineAllOfArrayAllofDogPropertyInnerAllOf1 read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ArrayOfInlineAllOfArrayAllofDogPropertyInnerAllOf1 instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ArrayOfNumberOnly.java

@@ -189,17 +189,18 @@ public class ArrayOfNumberOnly {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ArrayOfNumberOnly
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ArrayOfNumberOnly
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ArrayOfNumberOnly.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ArrayOfNumberOnly.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ArrayOfNumberOnly is not found in the empty JSON string", ArrayOfNumberOnly.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       // ensure the optional json data is an array if present
       if (jsonObj.get("ArrayNumber") != null && !jsonObj.get("ArrayNumber").isJsonArray()) {
         throw new IllegalArgumentException(String.format("Expected the field `ArrayNumber` to be an array in the JSON string but got `%s`", jsonObj.get("ArrayNumber").toString()));
@@ -243,8 +244,9 @@ public class ArrayOfNumberOnly {
 
            @Override
            public ArrayOfNumberOnly read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ArrayOfNumberOnly instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ArrayTest.java

@@ -261,17 +261,18 @@ public class ArrayTest {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ArrayTest
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ArrayTest
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ArrayTest.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ArrayTest.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ArrayTest is not found in the empty JSON string", ArrayTest.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       // ensure the optional json data is an array if present
       if (jsonObj.get("array_of_string") != null && !jsonObj.get("array_of_string").isJsonArray()) {
         throw new IllegalArgumentException(String.format("Expected the field `array_of_string` to be an array in the JSON string but got `%s`", jsonObj.get("array_of_string").toString()));
@@ -323,8 +324,9 @@ public class ArrayTest {
 
            @Override
            public ArrayTest read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ArrayTest instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Banana.java

@@ -179,17 +179,18 @@ public class Banana {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Banana
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Banana
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!Banana.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Banana.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in Banana is not found in the empty JSON string", Banana.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
   }
 
   public static class CustomTypeAdapterFactory implements TypeAdapterFactory {
@@ -229,8 +230,9 @@ public class Banana {
 
            @Override
            public Banana read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              Banana instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/BananaReq.java

@@ -162,32 +162,33 @@ public class BananaReq {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to BananaReq
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to BananaReq
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!BananaReq.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!BananaReq.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in BananaReq is not found in the empty JSON string", BananaReq.openapiRequiredFields.toString()));
         }
       }
 
-      Set<Entry<String, JsonElement>> entries = jsonObj.entrySet();
+      Set<Entry<String, JsonElement>> entries = jsonElement.getAsJsonObject().entrySet();
       // check to see if the JSON string contains additional fields
       for (Entry<String, JsonElement> entry : entries) {
         if (!BananaReq.openapiFields.contains(entry.getKey())) {
-          throw new IllegalArgumentException(String.format("The field `%s` in the JSON string is not defined in the `BananaReq` properties. JSON: %s", entry.getKey(), jsonObj.toString()));
+          throw new IllegalArgumentException(String.format("The field `%s` in the JSON string is not defined in the `BananaReq` properties. JSON: %s", entry.getKey(), jsonElement.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : BananaReq.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
   }
 
   public static class CustomTypeAdapterFactory implements TypeAdapterFactory {
@@ -210,9 +211,9 @@ public class BananaReq {
 
            @Override
            public BananaReq read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
-             return thisAdapter.fromJsonTree(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             return thisAdapter.fromJsonTree(jsonElement);
            }
 
        }.nullSafe();

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/BasquePig.java

@@ -179,24 +179,25 @@ public class BasquePig {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to BasquePig
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to BasquePig
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!BasquePig.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!BasquePig.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in BasquePig is not found in the empty JSON string", BasquePig.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : BasquePig.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if (!jsonObj.get("className").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `className` to be a primitive type in the JSON string but got `%s`", jsonObj.get("className").toString()));
       }
@@ -239,8 +240,9 @@ public class BasquePig {
 
            @Override
            public BasquePig read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              BasquePig instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Capitalization.java

@@ -318,17 +318,18 @@ public class Capitalization {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Capitalization
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Capitalization
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!Capitalization.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Capitalization.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in Capitalization is not found in the empty JSON string", Capitalization.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("smallCamel") != null && !jsonObj.get("smallCamel").isJsonNull()) && !jsonObj.get("smallCamel").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `smallCamel` to be a primitive type in the JSON string but got `%s`", jsonObj.get("smallCamel").toString()));
       }
@@ -386,8 +387,9 @@ public class Capitalization {
 
            @Override
            public Capitalization read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              Capitalization instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Cat.java

@@ -185,22 +185,22 @@ public class Cat extends Animal {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Cat
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Cat
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!Cat.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Cat.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in Cat is not found in the empty JSON string", Cat.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : Cat.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
   }
@@ -242,8 +242,9 @@ public class Cat extends Animal {
 
            @Override
            public Cat read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              Cat instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Category.java

@@ -207,24 +207,25 @@ public class Category {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Category
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Category
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!Category.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Category.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in Category is not found in the empty JSON string", Category.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : Category.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if (!jsonObj.get("name").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `name` to be a primitive type in the JSON string but got `%s`", jsonObj.get("name").toString()));
       }
@@ -267,8 +268,9 @@ public class Category {
 
            @Override
            public Category read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              Category instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ClassModel.java

@@ -178,17 +178,18 @@ public class ClassModel {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ClassModel
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ClassModel
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ClassModel.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ClassModel.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ClassModel is not found in the empty JSON string", ClassModel.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("_class") != null && !jsonObj.get("_class").isJsonNull()) && !jsonObj.get("_class").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `_class` to be a primitive type in the JSON string but got `%s`", jsonObj.get("_class").toString()));
       }
@@ -231,8 +232,9 @@ public class ClassModel {
 
            @Override
            public ClassModel read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ClassModel instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Client.java

@@ -178,17 +178,18 @@ public class Client {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Client
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Client
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!Client.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Client.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in Client is not found in the empty JSON string", Client.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("client") != null && !jsonObj.get("client").isJsonNull()) && !jsonObj.get("client").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `client` to be a primitive type in the JSON string but got `%s`", jsonObj.get("client").toString()));
       }
@@ -231,8 +232,9 @@ public class Client {
 
            @Override
            public Client read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              Client instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ComplexQuadrilateral.java

@@ -208,24 +208,25 @@ public class ComplexQuadrilateral {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ComplexQuadrilateral
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ComplexQuadrilateral
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ComplexQuadrilateral.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ComplexQuadrilateral.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ComplexQuadrilateral is not found in the empty JSON string", ComplexQuadrilateral.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : ComplexQuadrilateral.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if (!jsonObj.get("shapeType").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `shapeType` to be a primitive type in the JSON string but got `%s`", jsonObj.get("shapeType").toString()));
       }
@@ -271,8 +272,9 @@ public class ComplexQuadrilateral {
 
            @Override
            public ComplexQuadrilateral read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ComplexQuadrilateral instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/DanishPig.java

@@ -179,24 +179,25 @@ public class DanishPig {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to DanishPig
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to DanishPig
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!DanishPig.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!DanishPig.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in DanishPig is not found in the empty JSON string", DanishPig.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : DanishPig.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if (!jsonObj.get("className").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `className` to be a primitive type in the JSON string but got `%s`", jsonObj.get("className").toString()));
       }
@@ -239,8 +240,9 @@ public class DanishPig {
 
            @Override
            public DanishPig read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              DanishPig instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/DeprecatedObject.java

@@ -180,17 +180,18 @@ public class DeprecatedObject {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to DeprecatedObject
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to DeprecatedObject
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!DeprecatedObject.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!DeprecatedObject.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in DeprecatedObject is not found in the empty JSON string", DeprecatedObject.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("name") != null && !jsonObj.get("name").isJsonNull()) && !jsonObj.get("name").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `name` to be a primitive type in the JSON string but got `%s`", jsonObj.get("name").toString()));
       }
@@ -233,8 +234,9 @@ public class DeprecatedObject {
 
            @Override
            public DeprecatedObject read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              DeprecatedObject instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Dog.java

@@ -185,22 +185,22 @@ public class Dog extends Animal {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Dog
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Dog
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!Dog.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Dog.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in Dog is not found in the empty JSON string", Dog.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : Dog.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
   }
@@ -242,8 +242,9 @@ public class Dog extends Animal {
 
            @Override
            public Dog read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              Dog instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Drawing.java

@@ -242,36 +242,37 @@ public class Drawing {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Drawing
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Drawing
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!Drawing.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Drawing.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in Drawing is not found in the empty JSON string", Drawing.openapiRequiredFields.toString()));
         }
       }
 
-      Set<Entry<String, JsonElement>> entries = jsonObj.entrySet();
+      Set<Entry<String, JsonElement>> entries = jsonElement.getAsJsonObject().entrySet();
       // check to see if the JSON string contains additional fields
       for (Entry<String, JsonElement> entry : entries) {
         if (!Drawing.openapiFields.contains(entry.getKey())) {
-          throw new IllegalArgumentException(String.format("The field `%s` in the JSON string is not defined in the `Drawing` properties. JSON: %s", entry.getKey(), jsonObj.toString()));
+          throw new IllegalArgumentException(String.format("The field `%s` in the JSON string is not defined in the `Drawing` properties. JSON: %s", entry.getKey(), jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       // validate the optional field `mainShape`
       if (jsonObj.get("mainShape") != null && !jsonObj.get("mainShape").isJsonNull()) {
-        Shape.validateJsonObject(jsonObj.getAsJsonObject("mainShape"));
+        Shape.validateJsonElement(jsonObj.get("mainShape"));
       }
       // validate the optional field `shapeOrNull`
       if (jsonObj.get("shapeOrNull") != null && !jsonObj.get("shapeOrNull").isJsonNull()) {
-        ShapeOrNull.validateJsonObject(jsonObj.getAsJsonObject("shapeOrNull"));
+        ShapeOrNull.validateJsonElement(jsonObj.get("shapeOrNull"));
       }
       // validate the optional field `nullableShape`
       if (jsonObj.get("nullableShape") != null && !jsonObj.get("nullableShape").isJsonNull()) {
-        NullableShape.validateJsonObject(jsonObj.getAsJsonObject("nullableShape"));
+        NullableShape.validateJsonElement(jsonObj.get("nullableShape"));
       }
       if (jsonObj.get("shapes") != null && !jsonObj.get("shapes").isJsonNull()) {
         JsonArray jsonArrayshapes = jsonObj.getAsJsonArray("shapes");
@@ -283,7 +284,7 @@ public class Drawing {
 
           // validate the optional field `shapes` (array)
           for (int i = 0; i < jsonArrayshapes.size(); i++) {
-            Shape.validateJsonObject(jsonArrayshapes.get(i).getAsJsonObject());
+            Shape.validateJsonElement(jsonArrayshapes.get(i));
           };
         }
       }
@@ -309,9 +310,9 @@ public class Drawing {
 
            @Override
            public Drawing read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
-             return thisAdapter.fromJsonTree(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             return thisAdapter.fromJsonTree(jsonElement);
            }
 
        }.nullSafe();

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/EnumArrays.java

@@ -310,17 +310,18 @@ public class EnumArrays {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to EnumArrays
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to EnumArrays
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!EnumArrays.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!EnumArrays.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in EnumArrays is not found in the empty JSON string", EnumArrays.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("just_symbol") != null && !jsonObj.get("just_symbol").isJsonNull()) && !jsonObj.get("just_symbol").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `just_symbol` to be a primitive type in the JSON string but got `%s`", jsonObj.get("just_symbol").toString()));
       }
@@ -367,8 +368,9 @@ public class EnumArrays {
 
            @Override
            public EnumArrays read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              EnumArrays instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/EnumStringDiscriminator.java

@@ -226,22 +226,22 @@ public class EnumStringDiscriminator {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to EnumStringDiscriminator
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to EnumStringDiscriminator
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!EnumStringDiscriminator.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!EnumStringDiscriminator.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in EnumStringDiscriminator is not found in the empty JSON string", EnumStringDiscriminator.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : EnumStringDiscriminator.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
   }
@@ -283,8 +283,9 @@ public class EnumStringDiscriminator {
 
            @Override
            public EnumStringDiscriminator read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              EnumStringDiscriminator instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/EnumTest.java

@@ -658,24 +658,25 @@ public class EnumTest {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to EnumTest
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to EnumTest
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!EnumTest.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!EnumTest.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in EnumTest is not found in the empty JSON string", EnumTest.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : EnumTest.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("enum_string") != null && !jsonObj.get("enum_string").isJsonNull()) && !jsonObj.get("enum_string").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `enum_string` to be a primitive type in the JSON string but got `%s`", jsonObj.get("enum_string").toString()));
       }
@@ -721,8 +722,9 @@ public class EnumTest {
 
            @Override
            public EnumTest read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              EnumTest instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/EquilateralTriangle.java

@@ -208,24 +208,25 @@ public class EquilateralTriangle {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to EquilateralTriangle
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to EquilateralTriangle
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!EquilateralTriangle.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!EquilateralTriangle.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in EquilateralTriangle is not found in the empty JSON string", EquilateralTriangle.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : EquilateralTriangle.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if (!jsonObj.get("shapeType").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `shapeType` to be a primitive type in the JSON string but got `%s`", jsonObj.get("shapeType").toString()));
       }
@@ -271,8 +272,9 @@ public class EquilateralTriangle {
 
            @Override
            public EquilateralTriangle read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              EquilateralTriangle instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/FileSchemaTestClass.java

@@ -217,20 +217,21 @@ public class FileSchemaTestClass {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to FileSchemaTestClass
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to FileSchemaTestClass
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!FileSchemaTestClass.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!FileSchemaTestClass.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in FileSchemaTestClass is not found in the empty JSON string", FileSchemaTestClass.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       // validate the optional field `file`
       if (jsonObj.get("file") != null && !jsonObj.get("file").isJsonNull()) {
-        ModelFile.validateJsonObject(jsonObj.getAsJsonObject("file"));
+        ModelFile.validateJsonElement(jsonObj.get("file"));
       }
       if (jsonObj.get("files") != null && !jsonObj.get("files").isJsonNull()) {
         JsonArray jsonArrayfiles = jsonObj.getAsJsonArray("files");
@@ -242,7 +243,7 @@ public class FileSchemaTestClass {
 
           // validate the optional field `files` (array)
           for (int i = 0; i < jsonArrayfiles.size(); i++) {
-            ModelFile.validateJsonObject(jsonArrayfiles.get(i).getAsJsonObject());
+            ModelFile.validateJsonElement(jsonArrayfiles.get(i));
           };
         }
       }
@@ -285,8 +286,9 @@ public class FileSchemaTestClass {
 
            @Override
            public FileSchemaTestClass read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              FileSchemaTestClass instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Foo.java

@@ -178,17 +178,18 @@ public class Foo {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Foo
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Foo
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!Foo.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Foo.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in Foo is not found in the empty JSON string", Foo.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("bar") != null && !jsonObj.get("bar").isJsonNull()) && !jsonObj.get("bar").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `bar` to be a primitive type in the JSON string but got `%s`", jsonObj.get("bar").toString()));
       }
@@ -231,8 +232,9 @@ public class Foo {
 
            @Override
            public Foo read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              Foo instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/FooGetDefaultResponse.java

@@ -179,20 +179,21 @@ public class FooGetDefaultResponse {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to FooGetDefaultResponse
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to FooGetDefaultResponse
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!FooGetDefaultResponse.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!FooGetDefaultResponse.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in FooGetDefaultResponse is not found in the empty JSON string", FooGetDefaultResponse.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       // validate the optional field `string`
       if (jsonObj.get("string") != null && !jsonObj.get("string").isJsonNull()) {
-        Foo.validateJsonObject(jsonObj.getAsJsonObject("string"));
+        Foo.validateJsonElement(jsonObj.get("string"));
       }
   }
 
@@ -233,8 +234,9 @@ public class FooGetDefaultResponse {
 
            @Override
            public FooGetDefaultResponse read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              FooGetDefaultResponse instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/FormatTest.java

@@ -645,24 +645,25 @@ public class FormatTest {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to FormatTest
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to FormatTest
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!FormatTest.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!FormatTest.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in FormatTest is not found in the empty JSON string", FormatTest.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : FormatTest.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("string") != null && !jsonObj.get("string").isJsonNull()) && !jsonObj.get("string").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `string` to be a primitive type in the JSON string but got `%s`", jsonObj.get("string").toString()));
       }
@@ -720,8 +721,9 @@ public class FormatTest {
 
            @Override
            public FormatTest read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              FormatTest instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Fruit.java

@@ -35,6 +35,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import com.google.gson.Gson;
@@ -54,6 +55,7 @@ import com.google.gson.JsonSerializationContext;
 import com.google.gson.JsonSerializer;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
+import com.google.gson.JsonArray;
 import com.google.gson.JsonParseException;
 
 import org.openapitools.client.JSON;
@@ -83,25 +85,23 @@ public class Fruit extends AbstractOpenApiSchema {
 
                     // check if the actual instance is of the type `Apple`
                     if (value.getActualInstance() instanceof Apple) {
-                        JsonObject obj = adapterApple.toJsonTree((Apple)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
+                      JsonElement element = adapterApple.toJsonTree((Apple)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
                     }
-
                     // check if the actual instance is of the type `Banana`
                     if (value.getActualInstance() instanceof Banana) {
-                        JsonObject obj = adapterBanana.toJsonTree((Banana)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
+                      JsonElement element = adapterBanana.toJsonTree((Banana)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
                     }
-
                     throw new IOException("Failed to serialize as the type doesn't match oneOf schemas: Apple, Banana");
                 }
 
                 @Override
                 public Fruit read(JsonReader in) throws IOException {
                     Object deserialized = null;
-                    JsonObject jsonObject = elementAdapter.read(in).getAsJsonObject();
+                    JsonElement jsonElement = elementAdapter.read(in);
 
                     int match = 0;
                     ArrayList<String> errorMessages = new ArrayList<>();
@@ -109,37 +109,36 @@ public class Fruit extends AbstractOpenApiSchema {
 
                     // deserialize Apple
                     try {
-                        // validate the JSON object to see if any exception is thrown
-                        Apple.validateJsonObject(jsonObject);
-                        actualAdapter = adapterApple;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'Apple'");
+                      // validate the JSON object to see if any exception is thrown
+                      Apple.validateJsonElement(jsonElement);
+                      actualAdapter = adapterApple;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'Apple'");
                     } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for Apple failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'Apple'", e);
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for Apple failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'Apple'", e);
                     }
-
                     // deserialize Banana
                     try {
-                        // validate the JSON object to see if any exception is thrown
-                        Banana.validateJsonObject(jsonObject);
-                        actualAdapter = adapterBanana;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'Banana'");
+                      // validate the JSON object to see if any exception is thrown
+                      Banana.validateJsonElement(jsonElement);
+                      actualAdapter = adapterBanana;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'Banana'");
                     } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for Banana failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'Banana'", e);
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for Banana failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'Banana'", e);
                     }
 
                     if (match == 1) {
                         Fruit ret = new Fruit();
-                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonObject));
+                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonElement));
                         return ret;
                     }
 
-                    throw new IOException(String.format("Failed deserialization for Fruit: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonObject.toString()));
+                    throw new IOException(String.format("Failed deserialization for Fruit: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonElement.toString()));
                 }
             }.nullSafe();
         }
@@ -216,7 +215,6 @@ public class Fruit extends AbstractOpenApiSchema {
     public Apple getApple() throws ClassCastException {
         return (Apple)super.getActualInstance();
     }
-
     /**
      * Get the actual instance of `Banana`. If the actual instance is not `Banana`,
      * the ClassCastException will be thrown.
@@ -228,20 +226,19 @@ public class Fruit extends AbstractOpenApiSchema {
         return (Banana)super.getActualInstance();
     }
 
-
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Fruit
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Fruit
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
     // validate oneOf schemas one by one
     int validCount = 0;
     ArrayList<String> errorMessages = new ArrayList<>();
     // validate the json string with Apple
     try {
-      Apple.validateJsonObject(jsonObj);
+      Apple.validateJsonElement(jsonElement);
       validCount++;
     } catch (Exception e) {
       errorMessages.add(String.format("Deserialization for Apple failed with `%s`.", e.getMessage()));
@@ -249,14 +246,14 @@ public class Fruit extends AbstractOpenApiSchema {
     }
     // validate the json string with Banana
     try {
-      Banana.validateJsonObject(jsonObj);
+      Banana.validateJsonElement(jsonElement);
       validCount++;
     } catch (Exception e) {
       errorMessages.add(String.format("Deserialization for Banana failed with `%s`.", e.getMessage()));
       // continue to the next one
     }
     if (validCount != 1) {
-      throw new IOException(String.format("The JSON string is invalid for Fruit with oneOf schemas: Apple, Banana. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonObj.toString()));
+      throw new IOException(String.format("The JSON string is invalid for Fruit with oneOf schemas: Apple, Banana. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonElement.toString()));
     }
   }
 

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/FruitReq.java

@@ -35,6 +35,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import com.google.gson.Gson;
@@ -54,6 +55,7 @@ import com.google.gson.JsonSerializationContext;
 import com.google.gson.JsonSerializer;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
+import com.google.gson.JsonArray;
 import com.google.gson.JsonParseException;
 
 import org.openapitools.client.JSON;
@@ -83,25 +85,23 @@ public class FruitReq extends AbstractOpenApiSchema {
 
                     // check if the actual instance is of the type `AppleReq`
                     if (value.getActualInstance() instanceof AppleReq) {
-                        JsonObject obj = adapterAppleReq.toJsonTree((AppleReq)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
+                      JsonElement element = adapterAppleReq.toJsonTree((AppleReq)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
                     }
-
                     // check if the actual instance is of the type `BananaReq`
                     if (value.getActualInstance() instanceof BananaReq) {
-                        JsonObject obj = adapterBananaReq.toJsonTree((BananaReq)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
+                      JsonElement element = adapterBananaReq.toJsonTree((BananaReq)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
                     }
-
                     throw new IOException("Failed to serialize as the type doesn't match oneOf schemas: AppleReq, BananaReq");
                 }
 
                 @Override
                 public FruitReq read(JsonReader in) throws IOException {
                     Object deserialized = null;
-                    JsonObject jsonObject = elementAdapter.read(in).getAsJsonObject();
+                    JsonElement jsonElement = elementAdapter.read(in);
 
                     int match = 0;
                     ArrayList<String> errorMessages = new ArrayList<>();
@@ -109,37 +109,36 @@ public class FruitReq extends AbstractOpenApiSchema {
 
                     // deserialize AppleReq
                     try {
-                        // validate the JSON object to see if any exception is thrown
-                        AppleReq.validateJsonObject(jsonObject);
-                        actualAdapter = adapterAppleReq;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'AppleReq'");
+                      // validate the JSON object to see if any exception is thrown
+                      AppleReq.validateJsonElement(jsonElement);
+                      actualAdapter = adapterAppleReq;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'AppleReq'");
                     } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for AppleReq failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'AppleReq'", e);
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for AppleReq failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'AppleReq'", e);
                     }
-
                     // deserialize BananaReq
                     try {
-                        // validate the JSON object to see if any exception is thrown
-                        BananaReq.validateJsonObject(jsonObject);
-                        actualAdapter = adapterBananaReq;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'BananaReq'");
+                      // validate the JSON object to see if any exception is thrown
+                      BananaReq.validateJsonElement(jsonElement);
+                      actualAdapter = adapterBananaReq;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'BananaReq'");
                     } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for BananaReq failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'BananaReq'", e);
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for BananaReq failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'BananaReq'", e);
                     }
 
                     if (match == 1) {
                         FruitReq ret = new FruitReq();
-                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonObject));
+                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonElement));
                         return ret;
                     }
 
-                    throw new IOException(String.format("Failed deserialization for FruitReq: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonObject.toString()));
+                    throw new IOException(String.format("Failed deserialization for FruitReq: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonElement.toString()));
                 }
             }.nullSafe();
         }
@@ -221,7 +220,6 @@ public class FruitReq extends AbstractOpenApiSchema {
     public AppleReq getAppleReq() throws ClassCastException {
         return (AppleReq)super.getActualInstance();
     }
-
     /**
      * Get the actual instance of `BananaReq`. If the actual instance is not `BananaReq`,
      * the ClassCastException will be thrown.
@@ -233,20 +231,19 @@ public class FruitReq extends AbstractOpenApiSchema {
         return (BananaReq)super.getActualInstance();
     }
 
-
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to FruitReq
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to FruitReq
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
     // validate oneOf schemas one by one
     int validCount = 0;
     ArrayList<String> errorMessages = new ArrayList<>();
     // validate the json string with AppleReq
     try {
-      AppleReq.validateJsonObject(jsonObj);
+      AppleReq.validateJsonElement(jsonElement);
       validCount++;
     } catch (Exception e) {
       errorMessages.add(String.format("Deserialization for AppleReq failed with `%s`.", e.getMessage()));
@@ -254,14 +251,14 @@ public class FruitReq extends AbstractOpenApiSchema {
     }
     // validate the json string with BananaReq
     try {
-      BananaReq.validateJsonObject(jsonObj);
+      BananaReq.validateJsonElement(jsonElement);
       validCount++;
     } catch (Exception e) {
       errorMessages.add(String.format("Deserialization for BananaReq failed with `%s`.", e.getMessage()));
       // continue to the next one
     }
     if (validCount != 1) {
-      throw new IOException(String.format("The JSON string is invalid for FruitReq with oneOf schemas: AppleReq, BananaReq. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonObj.toString()));
+      throw new IOException(String.format("The JSON string is invalid for FruitReq with oneOf schemas: AppleReq, BananaReq. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonElement.toString()));
     }
   }
 

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/GmFruit.java

@@ -101,15 +101,15 @@ public class GmFruit extends AbstractOpenApiSchema {
                 @Override
                 public GmFruit read(JsonReader in) throws IOException {
                     Object deserialized = null;
-                    JsonObject jsonObject = elementAdapter.read(in).getAsJsonObject();
+                    JsonElement jsonElement = elementAdapter.read(in);
 
                     // deserialize Apple
                     try {
                         // validate the JSON object to see if any exception is thrown
-                        Apple.validateJsonObject(jsonObject);
+                        Apple.validateJsonElement(jsonElement);
                         log.log(Level.FINER, "Input data matches schema 'Apple'");
                         GmFruit ret = new GmFruit();
-                        ret.setActualInstance(adapterApple.fromJsonTree(jsonObject));
+                        ret.setActualInstance(adapterApple.fromJsonTree(jsonElement));
                         return ret;
                     } catch (Exception e) {
                         // deserialization failed, continue
@@ -119,10 +119,10 @@ public class GmFruit extends AbstractOpenApiSchema {
                     // deserialize Banana
                     try {
                         // validate the JSON object to see if any exception is thrown
-                        Banana.validateJsonObject(jsonObject);
+                        Banana.validateJsonElement(jsonElement);
                         log.log(Level.FINER, "Input data matches schema 'Banana'");
                         GmFruit ret = new GmFruit();
-                        ret.setActualInstance(adapterBanana.fromJsonTree(jsonObject));
+                        ret.setActualInstance(adapterBanana.fromJsonTree(jsonElement));
                         return ret;
                     } catch (Exception e) {
                         // deserialization failed, continue
@@ -130,7 +130,7 @@ public class GmFruit extends AbstractOpenApiSchema {
                     }
 
 
-                    throw new IOException(String.format("Failed deserialization for GmFruit: no class matched. JSON: %s", jsonObject.toString()));
+                    throw new IOException(String.format("Failed deserialization for GmFruit: no class matched. JSON: %s", jsonElement.toString()));
                 }
             }.nullSafe();
         }
@@ -221,17 +221,17 @@ public class GmFruit extends AbstractOpenApiSchema {
 
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to GmFruit
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to GmFruit
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
     // validate anyOf schemas one by one
     int validCount = 0;
     // validate the json string with Apple
     try {
-      Apple.validateJsonObject(jsonObj);
+      Apple.validateJsonElement(jsonElement);
       return; // return earlier as at least one schema is valid with respect to the Json object
       //validCount++;
     } catch (Exception e) {
@@ -239,14 +239,14 @@ public class GmFruit extends AbstractOpenApiSchema {
     }
     // validate the json string with Banana
     try {
-      Banana.validateJsonObject(jsonObj);
+      Banana.validateJsonElement(jsonElement);
       return; // return earlier as at least one schema is valid with respect to the Json object
       //validCount++;
     } catch (Exception e) {
       // continue to the next one
     }
     if (validCount == 0) {
-      throw new IOException(String.format("The JSON string is invalid for GmFruit with anyOf schemas: Apple, Banana. JSON: %s", jsonObj.toString()));
+      throw new IOException(String.format("The JSON string is invalid for GmFruit with anyOf schemas: Apple, Banana. JSON: %s", jsonElement.toString()));
     }
   }
 

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/GrandparentAnimal.java

@@ -180,22 +180,22 @@ public class GrandparentAnimal {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to GrandparentAnimal
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to GrandparentAnimal
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!GrandparentAnimal.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!GrandparentAnimal.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in GrandparentAnimal is not found in the empty JSON string", GrandparentAnimal.openapiRequiredFields.toString()));
         }
       }
 
-      String discriminatorValue = jsonObj.get("pet_type").getAsString();
+      String discriminatorValue = jsonElement.getAsJsonObject().get("pet_type").getAsString();
       switch (discriminatorValue) {
         case "ParentPet":
-          ParentPet.validateJsonObject(jsonObj);
+          ParentPet.validateJsonElement(jsonElement);
           break;
         default:
           throw new IllegalArgumentException(String.format("The value of the `pet_type` field `%s` does not match any key defined in the discriminator's mapping.", discriminatorValue));

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/HasOnlyReadOnly.java

@@ -198,17 +198,18 @@ public class HasOnlyReadOnly {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to HasOnlyReadOnly
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to HasOnlyReadOnly
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!HasOnlyReadOnly.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!HasOnlyReadOnly.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in HasOnlyReadOnly is not found in the empty JSON string", HasOnlyReadOnly.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("bar") != null && !jsonObj.get("bar").isJsonNull()) && !jsonObj.get("bar").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `bar` to be a primitive type in the JSON string but got `%s`", jsonObj.get("bar").toString()));
       }
@@ -254,8 +255,9 @@ public class HasOnlyReadOnly {
 
            @Override
            public HasOnlyReadOnly read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              HasOnlyReadOnly instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/HealthCheckResult.java

@@ -190,17 +190,18 @@ public class HealthCheckResult {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to HealthCheckResult
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to HealthCheckResult
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!HealthCheckResult.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!HealthCheckResult.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in HealthCheckResult is not found in the empty JSON string", HealthCheckResult.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("NullableMessage") != null && !jsonObj.get("NullableMessage").isJsonNull()) && !jsonObj.get("NullableMessage").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `NullableMessage` to be a primitive type in the JSON string but got `%s`", jsonObj.get("NullableMessage").toString()));
       }
@@ -243,8 +244,9 @@ public class HealthCheckResult {
 
            @Override
            public HealthCheckResult read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              HealthCheckResult instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/IsoscelesTriangle.java

@@ -162,32 +162,33 @@ public class IsoscelesTriangle {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to IsoscelesTriangle
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to IsoscelesTriangle
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!IsoscelesTriangle.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!IsoscelesTriangle.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in IsoscelesTriangle is not found in the empty JSON string", IsoscelesTriangle.openapiRequiredFields.toString()));
         }
       }
 
-      Set<Entry<String, JsonElement>> entries = jsonObj.entrySet();
+      Set<Entry<String, JsonElement>> entries = jsonElement.getAsJsonObject().entrySet();
       // check to see if the JSON string contains additional fields
       for (Entry<String, JsonElement> entry : entries) {
         if (!IsoscelesTriangle.openapiFields.contains(entry.getKey())) {
-          throw new IllegalArgumentException(String.format("The field `%s` in the JSON string is not defined in the `IsoscelesTriangle` properties. JSON: %s", entry.getKey(), jsonObj.toString()));
+          throw new IllegalArgumentException(String.format("The field `%s` in the JSON string is not defined in the `IsoscelesTriangle` properties. JSON: %s", entry.getKey(), jsonElement.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : IsoscelesTriangle.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if (!jsonObj.get("shapeType").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `shapeType` to be a primitive type in the JSON string but got `%s`", jsonObj.get("shapeType").toString()));
       }
@@ -216,9 +217,9 @@ public class IsoscelesTriangle {
 
            @Override
            public IsoscelesTriangle read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
-             return thisAdapter.fromJsonTree(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             return thisAdapter.fromJsonTree(jsonElement);
            }
 
        }.nullSafe();

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Mammal.java

@@ -35,6 +35,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import com.google.gson.Gson;
@@ -54,6 +55,7 @@ import com.google.gson.JsonSerializationContext;
 import com.google.gson.JsonSerializer;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
+import com.google.gson.JsonArray;
 import com.google.gson.JsonParseException;
 
 import org.openapitools.client.JSON;
@@ -70,9 +72,9 @@ public class Mammal extends AbstractOpenApiSchema {
                 return null; // this class only serializes 'Mammal' and its subtypes
             }
             final TypeAdapter<JsonElement> elementAdapter = gson.getAdapter(JsonElement.class);
-            final TypeAdapter<Pig> adapterPig = gson.getDelegateAdapter(this, TypeToken.get(Pig.class));
             final TypeAdapter<Whale> adapterWhale = gson.getDelegateAdapter(this, TypeToken.get(Whale.class));
             final TypeAdapter<Zebra> adapterZebra = gson.getDelegateAdapter(this, TypeToken.get(Zebra.class));
+            final TypeAdapter<Pig> adapterPig = gson.getDelegateAdapter(this, TypeToken.get(Pig.class));
 
             return (TypeAdapter<T>) new TypeAdapter<Mammal>() {
                 @Override
@@ -82,34 +84,33 @@ public class Mammal extends AbstractOpenApiSchema {
                         return;
                     }
 
-                    // check if the actual instance is of the type `Pig`
-                    if (value.getActualInstance() instanceof Pig) {
-                        JsonObject obj = adapterPig.toJsonTree((Pig)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
-                    }
-
                     // check if the actual instance is of the type `Whale`
                     if (value.getActualInstance() instanceof Whale) {
-                        JsonObject obj = adapterWhale.toJsonTree((Whale)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
+                      JsonElement element = adapterWhale.toJsonTree((Whale)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
                     }
-
                     // check if the actual instance is of the type `Zebra`
                     if (value.getActualInstance() instanceof Zebra) {
-                        JsonObject obj = adapterZebra.toJsonTree((Zebra)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
+                      JsonElement element = adapterZebra.toJsonTree((Zebra)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
+                    }
+                    // check if the actual instance is of the type `Pig`
+                    if (value.getActualInstance() instanceof Pig) {
+                      JsonElement element = adapterPig.toJsonTree((Pig)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
                     }
-
                     throw new IOException("Failed to serialize as the type doesn't match oneOf schemas: Pig, Whale, Zebra");
                 }
 
                 @Override
                 public Mammal read(JsonReader in) throws IOException {
                     Object deserialized = null;
-                    JsonObject jsonObject = elementAdapter.read(in).getAsJsonObject();
+                    JsonElement jsonElement = elementAdapter.read(in);
+
+                    JsonObject jsonObject = jsonElement.getAsJsonObject();
 
                     // use discriminator value for faster oneOf lookup
                     Mammal newMammal = new Mammal();
@@ -139,52 +140,50 @@ public class Mammal extends AbstractOpenApiSchema {
                     ArrayList<String> errorMessages = new ArrayList<>();
                     TypeAdapter actualAdapter = elementAdapter;
 
-                    // deserialize Pig
-                    try {
-                        // validate the JSON object to see if any exception is thrown
-                        Pig.validateJsonObject(jsonObject);
-                        actualAdapter = adapterPig;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'Pig'");
-                    } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for Pig failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'Pig'", e);
-                    }
-
                     // deserialize Whale
                     try {
-                        // validate the JSON object to see if any exception is thrown
-                        Whale.validateJsonObject(jsonObject);
-                        actualAdapter = adapterWhale;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'Whale'");
+                      // validate the JSON object to see if any exception is thrown
+                      Whale.validateJsonElement(jsonElement);
+                      actualAdapter = adapterWhale;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'Whale'");
                     } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for Whale failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'Whale'", e);
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for Whale failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'Whale'", e);
                     }
-
                     // deserialize Zebra
                     try {
-                        // validate the JSON object to see if any exception is thrown
-                        Zebra.validateJsonObject(jsonObject);
-                        actualAdapter = adapterZebra;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'Zebra'");
+                      // validate the JSON object to see if any exception is thrown
+                      Zebra.validateJsonElement(jsonElement);
+                      actualAdapter = adapterZebra;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'Zebra'");
                     } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for Zebra failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'Zebra'", e);
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for Zebra failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'Zebra'", e);
+                    }
+                    // deserialize Pig
+                    try {
+                      // validate the JSON object to see if any exception is thrown
+                      Pig.validateJsonElement(jsonElement);
+                      actualAdapter = adapterPig;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'Pig'");
+                    } catch (Exception e) {
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for Pig failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'Pig'", e);
                     }
 
                     if (match == 1) {
                         Mammal ret = new Mammal();
-                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonObject));
+                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonElement));
                         return ret;
                     }
 
-                    throw new IOException(String.format("Failed deserialization for Mammal: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonObject.toString()));
+                    throw new IOException(String.format("Failed deserialization for Mammal: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonElement.toString()));
                 }
             }.nullSafe();
         }
@@ -213,9 +212,9 @@ public class Mammal extends AbstractOpenApiSchema {
     }
 
     static {
-        schemas.put("Pig", Pig.class);
         schemas.put("Whale", Whale.class);
         schemas.put("Zebra", Zebra.class);
+        schemas.put("Pig", Pig.class);
     }
 
     @Override
@@ -233,11 +232,6 @@ public class Mammal extends AbstractOpenApiSchema {
      */
     @Override
     public void setActualInstance(Object instance) {
-        if (instance instanceof Pig) {
-            super.setActualInstance(instance);
-            return;
-        }
-
         if (instance instanceof Whale) {
             super.setActualInstance(instance);
             return;
@@ -248,6 +242,11 @@ public class Mammal extends AbstractOpenApiSchema {
             return;
         }
 
+        if (instance instanceof Pig) {
+            super.setActualInstance(instance);
+            return;
+        }
+
         throw new RuntimeException("Invalid instance type. Must be Pig, Whale, Zebra");
     }
 
@@ -262,17 +261,6 @@ public class Mammal extends AbstractOpenApiSchema {
         return super.getActualInstance();
     }
 
-    /**
-     * Get the actual instance of `Pig`. If the actual instance is not `Pig`,
-     * the ClassCastException will be thrown.
-     *
-     * @return The actual instance of `Pig`
-     * @throws ClassCastException if the instance is not `Pig`
-     */
-    public Pig getPig() throws ClassCastException {
-        return (Pig)super.getActualInstance();
-    }
-
     /**
      * Get the actual instance of `Whale`. If the actual instance is not `Whale`,
      * the ClassCastException will be thrown.
@@ -283,7 +271,6 @@ public class Mammal extends AbstractOpenApiSchema {
     public Whale getWhale() throws ClassCastException {
         return (Whale)super.getActualInstance();
     }
-
     /**
      * Get the actual instance of `Zebra`. If the actual instance is not `Zebra`,
      * the ClassCastException will be thrown.
@@ -294,29 +281,30 @@ public class Mammal extends AbstractOpenApiSchema {
     public Zebra getZebra() throws ClassCastException {
         return (Zebra)super.getActualInstance();
     }
-
+    /**
+     * Get the actual instance of `Pig`. If the actual instance is not `Pig`,
+     * the ClassCastException will be thrown.
+     *
+     * @return The actual instance of `Pig`
+     * @throws ClassCastException if the instance is not `Pig`
+     */
+    public Pig getPig() throws ClassCastException {
+        return (Pig)super.getActualInstance();
+    }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Mammal
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Mammal
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
     // validate oneOf schemas one by one
     int validCount = 0;
     ArrayList<String> errorMessages = new ArrayList<>();
-    // validate the json string with Pig
-    try {
-      Pig.validateJsonObject(jsonObj);
-      validCount++;
-    } catch (Exception e) {
-      errorMessages.add(String.format("Deserialization for Pig failed with `%s`.", e.getMessage()));
-      // continue to the next one
-    }
     // validate the json string with Whale
     try {
-      Whale.validateJsonObject(jsonObj);
+      Whale.validateJsonElement(jsonElement);
       validCount++;
     } catch (Exception e) {
       errorMessages.add(String.format("Deserialization for Whale failed with `%s`.", e.getMessage()));
@@ -324,14 +312,22 @@ public class Mammal extends AbstractOpenApiSchema {
     }
     // validate the json string with Zebra
     try {
-      Zebra.validateJsonObject(jsonObj);
+      Zebra.validateJsonElement(jsonElement);
       validCount++;
     } catch (Exception e) {
       errorMessages.add(String.format("Deserialization for Zebra failed with `%s`.", e.getMessage()));
       // continue to the next one
     }
+    // validate the json string with Pig
+    try {
+      Pig.validateJsonElement(jsonElement);
+      validCount++;
+    } catch (Exception e) {
+      errorMessages.add(String.format("Deserialization for Pig failed with `%s`.", e.getMessage()));
+      // continue to the next one
+    }
     if (validCount != 1) {
-      throw new IOException(String.format("The JSON string is invalid for Mammal with oneOf schemas: Pig, Whale, Zebra. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonObj.toString()));
+      throw new IOException(String.format("The JSON string is invalid for Mammal with oneOf schemas: Pig, Whale, Zebra. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonElement.toString()));
     }
   }
 

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/MapTest.java

@@ -343,17 +343,18 @@ public class MapTest {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to MapTest
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to MapTest
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!MapTest.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!MapTest.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in MapTest is not found in the empty JSON string", MapTest.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
   }
 
   public static class CustomTypeAdapterFactory implements TypeAdapterFactory {
@@ -393,8 +394,9 @@ public class MapTest {
 
            @Override
            public MapTest read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              MapTest instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/MixedPropertiesAndAdditionalPropertiesClass.java

@@ -247,17 +247,18 @@ public class MixedPropertiesAndAdditionalPropertiesClass {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to MixedPropertiesAndAdditionalPropertiesClass
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to MixedPropertiesAndAdditionalPropertiesClass
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!MixedPropertiesAndAdditionalPropertiesClass.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!MixedPropertiesAndAdditionalPropertiesClass.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in MixedPropertiesAndAdditionalPropertiesClass is not found in the empty JSON string", MixedPropertiesAndAdditionalPropertiesClass.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("uuid") != null && !jsonObj.get("uuid").isJsonNull()) && !jsonObj.get("uuid").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `uuid` to be a primitive type in the JSON string but got `%s`", jsonObj.get("uuid").toString()));
       }
@@ -300,8 +301,9 @@ public class MixedPropertiesAndAdditionalPropertiesClass {
 
            @Override
            public MixedPropertiesAndAdditionalPropertiesClass read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              MixedPropertiesAndAdditionalPropertiesClass instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Model200Response.java

@@ -206,17 +206,18 @@ public class Model200Response {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Model200Response
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Model200Response
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!Model200Response.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Model200Response.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in Model200Response is not found in the empty JSON string", Model200Response.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("class") != null && !jsonObj.get("class").isJsonNull()) && !jsonObj.get("class").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `class` to be a primitive type in the JSON string but got `%s`", jsonObj.get("class").toString()));
       }
@@ -259,8 +260,9 @@ public class Model200Response {
 
            @Override
            public Model200Response read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              Model200Response instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ModelApiResponse.java

@@ -234,17 +234,18 @@ public class ModelApiResponse {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ModelApiResponse
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ModelApiResponse
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ModelApiResponse.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ModelApiResponse.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ModelApiResponse is not found in the empty JSON string", ModelApiResponse.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("type") != null && !jsonObj.get("type").isJsonNull()) && !jsonObj.get("type").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `type` to be a primitive type in the JSON string but got `%s`", jsonObj.get("type").toString()));
       }
@@ -290,8 +291,9 @@ public class ModelApiResponse {
 
            @Override
            public ModelApiResponse read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ModelApiResponse instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ModelFile.java

@@ -178,17 +178,18 @@ public class ModelFile {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ModelFile
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ModelFile
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ModelFile.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ModelFile.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ModelFile is not found in the empty JSON string", ModelFile.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("sourceURI") != null && !jsonObj.get("sourceURI").isJsonNull()) && !jsonObj.get("sourceURI").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `sourceURI` to be a primitive type in the JSON string but got `%s`", jsonObj.get("sourceURI").toString()));
       }
@@ -231,8 +232,9 @@ public class ModelFile {
 
            @Override
            public ModelFile read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ModelFile instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ModelList.java

@@ -178,17 +178,18 @@ public class ModelList {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ModelList
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ModelList
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ModelList.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ModelList.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ModelList is not found in the empty JSON string", ModelList.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("123-list") != null && !jsonObj.get("123-list").isJsonNull()) && !jsonObj.get("123-list").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `123-list` to be a primitive type in the JSON string but got `%s`", jsonObj.get("123-list").toString()));
       }
@@ -231,8 +232,9 @@ public class ModelList {
 
            @Override
            public ModelList read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ModelList instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ModelReturn.java

@@ -178,17 +178,18 @@ public class ModelReturn {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ModelReturn
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ModelReturn
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ModelReturn.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ModelReturn.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ModelReturn is not found in the empty JSON string", ModelReturn.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
   }
 
   public static class CustomTypeAdapterFactory implements TypeAdapterFactory {
@@ -228,8 +229,9 @@ public class ModelReturn {
 
            @Override
            public ModelReturn read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ModelReturn instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Name.java

@@ -255,24 +255,25 @@ public class Name {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Name
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Name
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!Name.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Name.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in Name is not found in the empty JSON string", Name.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : Name.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("property") != null && !jsonObj.get("property").isJsonNull()) && !jsonObj.get("property").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `property` to be a primitive type in the JSON string but got `%s`", jsonObj.get("property").toString()));
       }
@@ -315,8 +316,9 @@ public class Name {
 
            @Override
            public Name read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              Name instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/NullableClass.java

@@ -507,25 +507,26 @@ public class NullableClass {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to NullableClass
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to NullableClass
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!NullableClass.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!NullableClass.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in NullableClass is not found in the empty JSON string", NullableClass.openapiRequiredFields.toString()));
         }
       }
 
-      Set<Entry<String, JsonElement>> entries = jsonObj.entrySet();
+      Set<Entry<String, JsonElement>> entries = jsonElement.getAsJsonObject().entrySet();
       // check to see if the JSON string contains additional fields
       for (Entry<String, JsonElement> entry : entries) {
         if (!NullableClass.openapiFields.contains(entry.getKey())) {
-          throw new IllegalArgumentException(String.format("The field `%s` in the JSON string is not defined in the `NullableClass` properties. JSON: %s", entry.getKey(), jsonObj.toString()));
+          throw new IllegalArgumentException(String.format("The field `%s` in the JSON string is not defined in the `NullableClass` properties. JSON: %s", entry.getKey(), jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("string_prop") != null && !jsonObj.get("string_prop").isJsonNull()) && !jsonObj.get("string_prop").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `string_prop` to be a primitive type in the JSON string but got `%s`", jsonObj.get("string_prop").toString()));
       }
@@ -563,9 +564,9 @@ public class NullableClass {
 
            @Override
            public NullableClass read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
-             return thisAdapter.fromJsonTree(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             return thisAdapter.fromJsonTree(jsonElement);
            }
 
        }.nullSafe();

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/NullableShape.java

@@ -34,6 +34,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import com.google.gson.Gson;
@@ -53,6 +54,7 @@ import com.google.gson.JsonSerializationContext;
 import com.google.gson.JsonSerializer;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
+import com.google.gson.JsonArray;
 import com.google.gson.JsonParseException;
 
 import org.openapitools.client.JSON;
@@ -69,8 +71,8 @@ public class NullableShape extends AbstractOpenApiSchema {
                 return null; // this class only serializes 'NullableShape' and its subtypes
             }
             final TypeAdapter<JsonElement> elementAdapter = gson.getAdapter(JsonElement.class);
-            final TypeAdapter<Quadrilateral> adapterQuadrilateral = gson.getDelegateAdapter(this, TypeToken.get(Quadrilateral.class));
             final TypeAdapter<Triangle> adapterTriangle = gson.getDelegateAdapter(this, TypeToken.get(Triangle.class));
+            final TypeAdapter<Quadrilateral> adapterQuadrilateral = gson.getDelegateAdapter(this, TypeToken.get(Quadrilateral.class));
 
             return (TypeAdapter<T>) new TypeAdapter<NullableShape>() {
                 @Override
@@ -80,27 +82,27 @@ public class NullableShape extends AbstractOpenApiSchema {
                         return;
                     }
 
-                    // check if the actual instance is of the type `Quadrilateral`
-                    if (value.getActualInstance() instanceof Quadrilateral) {
-                        JsonObject obj = adapterQuadrilateral.toJsonTree((Quadrilateral)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
-                    }
-
                     // check if the actual instance is of the type `Triangle`
                     if (value.getActualInstance() instanceof Triangle) {
-                        JsonObject obj = adapterTriangle.toJsonTree((Triangle)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
+                      JsonElement element = adapterTriangle.toJsonTree((Triangle)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
+                    }
+                    // check if the actual instance is of the type `Quadrilateral`
+                    if (value.getActualInstance() instanceof Quadrilateral) {
+                      JsonElement element = adapterQuadrilateral.toJsonTree((Quadrilateral)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
                     }
-
                     throw new IOException("Failed to serialize as the type doesn't match oneOf schemas: Quadrilateral, Triangle");
                 }
 
                 @Override
                 public NullableShape read(JsonReader in) throws IOException {
                     Object deserialized = null;
-                    JsonObject jsonObject = elementAdapter.read(in).getAsJsonObject();
+                    JsonElement jsonElement = elementAdapter.read(in);
+
+                    JsonObject jsonObject = jsonElement.getAsJsonObject();
 
                     // use discriminator value for faster oneOf lookup
                     NullableShape newNullableShape = new NullableShape();
@@ -126,39 +128,38 @@ public class NullableShape extends AbstractOpenApiSchema {
                     ArrayList<String> errorMessages = new ArrayList<>();
                     TypeAdapter actualAdapter = elementAdapter;
 
-                    // deserialize Quadrilateral
-                    try {
-                        // validate the JSON object to see if any exception is thrown
-                        Quadrilateral.validateJsonObject(jsonObject);
-                        actualAdapter = adapterQuadrilateral;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'Quadrilateral'");
-                    } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for Quadrilateral failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'Quadrilateral'", e);
-                    }
-
                     // deserialize Triangle
                     try {
-                        // validate the JSON object to see if any exception is thrown
-                        Triangle.validateJsonObject(jsonObject);
-                        actualAdapter = adapterTriangle;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'Triangle'");
+                      // validate the JSON object to see if any exception is thrown
+                      Triangle.validateJsonElement(jsonElement);
+                      actualAdapter = adapterTriangle;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'Triangle'");
                     } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for Triangle failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'Triangle'", e);
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for Triangle failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'Triangle'", e);
+                    }
+                    // deserialize Quadrilateral
+                    try {
+                      // validate the JSON object to see if any exception is thrown
+                      Quadrilateral.validateJsonElement(jsonElement);
+                      actualAdapter = adapterQuadrilateral;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'Quadrilateral'");
+                    } catch (Exception e) {
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for Quadrilateral failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'Quadrilateral'", e);
                     }
 
                     if (match == 1) {
                         NullableShape ret = new NullableShape();
-                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonObject));
+                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonElement));
                         return ret;
                     }
 
-                    throw new IOException(String.format("Failed deserialization for NullableShape: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonObject.toString()));
+                    throw new IOException(String.format("Failed deserialization for NullableShape: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonElement.toString()));
                 }
             }.nullSafe();
         }
@@ -182,8 +183,8 @@ public class NullableShape extends AbstractOpenApiSchema {
     }
 
     static {
-        schemas.put("Quadrilateral", Quadrilateral.class);
         schemas.put("Triangle", Triangle.class);
+        schemas.put("Quadrilateral", Quadrilateral.class);
     }
 
     @Override
@@ -206,12 +207,12 @@ public class NullableShape extends AbstractOpenApiSchema {
            return;
         }
 
-        if (instance instanceof Quadrilateral) {
+        if (instance instanceof Triangle) {
             super.setActualInstance(instance);
             return;
         }
 
-        if (instance instanceof Triangle) {
+        if (instance instanceof Quadrilateral) {
             super.setActualInstance(instance);
             return;
         }
@@ -230,6 +231,16 @@ public class NullableShape extends AbstractOpenApiSchema {
         return super.getActualInstance();
     }
 
+    /**
+     * Get the actual instance of `Triangle`. If the actual instance is not `Triangle`,
+     * the ClassCastException will be thrown.
+     *
+     * @return The actual instance of `Triangle`
+     * @throws ClassCastException if the instance is not `Triangle`
+     */
+    public Triangle getTriangle() throws ClassCastException {
+        return (Triangle)super.getActualInstance();
+    }
     /**
      * Get the actual instance of `Quadrilateral`. If the actual instance is not `Quadrilateral`,
      * the ClassCastException will be thrown.
@@ -241,46 +252,34 @@ public class NullableShape extends AbstractOpenApiSchema {
         return (Quadrilateral)super.getActualInstance();
     }
 
-    /**
-     * Get the actual instance of `Triangle`. If the actual instance is not `Triangle`,
-     * the ClassCastException will be thrown.
-     *
-     * @return The actual instance of `Triangle`
-     * @throws ClassCastException if the instance is not `Triangle`
-     */
-    public Triangle getTriangle() throws ClassCastException {
-        return (Triangle)super.getActualInstance();
-    }
-
-
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to NullableShape
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to NullableShape
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
     // validate oneOf schemas one by one
     int validCount = 0;
     ArrayList<String> errorMessages = new ArrayList<>();
-    // validate the json string with Quadrilateral
-    try {
-      Quadrilateral.validateJsonObject(jsonObj);
-      validCount++;
-    } catch (Exception e) {
-      errorMessages.add(String.format("Deserialization for Quadrilateral failed with `%s`.", e.getMessage()));
-      // continue to the next one
-    }
     // validate the json string with Triangle
     try {
-      Triangle.validateJsonObject(jsonObj);
+      Triangle.validateJsonElement(jsonElement);
       validCount++;
     } catch (Exception e) {
       errorMessages.add(String.format("Deserialization for Triangle failed with `%s`.", e.getMessage()));
       // continue to the next one
     }
+    // validate the json string with Quadrilateral
+    try {
+      Quadrilateral.validateJsonElement(jsonElement);
+      validCount++;
+    } catch (Exception e) {
+      errorMessages.add(String.format("Deserialization for Quadrilateral failed with `%s`.", e.getMessage()));
+      // continue to the next one
+    }
     if (validCount != 1) {
-      throw new IOException(String.format("The JSON string is invalid for NullableShape with oneOf schemas: Quadrilateral, Triangle. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonObj.toString()));
+      throw new IOException(String.format("The JSON string is invalid for NullableShape with oneOf schemas: Quadrilateral, Triangle. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonElement.toString()));
     }
   }
 

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/NumberOnly.java

@@ -179,17 +179,18 @@ public class NumberOnly {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to NumberOnly
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to NumberOnly
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!NumberOnly.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!NumberOnly.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in NumberOnly is not found in the empty JSON string", NumberOnly.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
   }
 
   public static class CustomTypeAdapterFactory implements TypeAdapterFactory {
@@ -229,8 +230,9 @@ public class NumberOnly {
 
            @Override
            public NumberOnly read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              NumberOnly instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ObjectWithDeprecatedFields.java

@@ -289,23 +289,24 @@ public class ObjectWithDeprecatedFields {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ObjectWithDeprecatedFields
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ObjectWithDeprecatedFields
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ObjectWithDeprecatedFields.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ObjectWithDeprecatedFields.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ObjectWithDeprecatedFields is not found in the empty JSON string", ObjectWithDeprecatedFields.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("uuid") != null && !jsonObj.get("uuid").isJsonNull()) && !jsonObj.get("uuid").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `uuid` to be a primitive type in the JSON string but got `%s`", jsonObj.get("uuid").toString()));
       }
       // validate the optional field `deprecatedRef`
       if (jsonObj.get("deprecatedRef") != null && !jsonObj.get("deprecatedRef").isJsonNull()) {
-        DeprecatedObject.validateJsonObject(jsonObj.getAsJsonObject("deprecatedRef"));
+        DeprecatedObject.validateJsonElement(jsonObj.get("deprecatedRef"));
       }
       // ensure the optional json data is an array if present
       if (jsonObj.get("bars") != null && !jsonObj.get("bars").isJsonArray()) {
@@ -350,8 +351,9 @@ public class ObjectWithDeprecatedFields {
 
            @Override
            public ObjectWithDeprecatedFields read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ObjectWithDeprecatedFields instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Order.java

@@ -368,17 +368,18 @@ public class Order {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Order
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Order
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!Order.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Order.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in Order is not found in the empty JSON string", Order.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("status") != null && !jsonObj.get("status").isJsonNull()) && !jsonObj.get("status").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `status` to be a primitive type in the JSON string but got `%s`", jsonObj.get("status").toString()));
       }
@@ -421,8 +422,9 @@ public class Order {
 
            @Override
            public Order read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              Order instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/OuterComposite.java

@@ -235,17 +235,18 @@ public class OuterComposite {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to OuterComposite
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to OuterComposite
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!OuterComposite.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!OuterComposite.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in OuterComposite is not found in the empty JSON string", OuterComposite.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("my_string") != null && !jsonObj.get("my_string").isJsonNull()) && !jsonObj.get("my_string").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `my_string` to be a primitive type in the JSON string but got `%s`", jsonObj.get("my_string").toString()));
       }
@@ -288,8 +289,9 @@ public class OuterComposite {
 
            @Override
            public OuterComposite read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              OuterComposite instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ParentPet.java

@@ -154,22 +154,22 @@ public class ParentPet extends GrandparentAnimal {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ParentPet
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ParentPet
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ParentPet.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ParentPet.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ParentPet is not found in the empty JSON string", ParentPet.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : ParentPet.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
   }
@@ -211,8 +211,9 @@ public class ParentPet extends GrandparentAnimal {
 
            @Override
            public ParentPet read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ParentPet instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Pet.java

@@ -389,27 +389,28 @@ public class Pet {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Pet
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Pet
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!Pet.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Pet.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in Pet is not found in the empty JSON string", Pet.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : Pet.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       // validate the optional field `category`
       if (jsonObj.get("category") != null && !jsonObj.get("category").isJsonNull()) {
-        Category.validateJsonObject(jsonObj.getAsJsonObject("category"));
+        Category.validateJsonElement(jsonObj.get("category"));
       }
       if (!jsonObj.get("name").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `name` to be a primitive type in the JSON string but got `%s`", jsonObj.get("name").toString()));
@@ -430,7 +431,7 @@ public class Pet {
 
           // validate the optional field `tags` (array)
           for (int i = 0; i < jsonArraytags.size(); i++) {
-            Tag.validateJsonObject(jsonArraytags.get(i).getAsJsonObject());
+            Tag.validateJsonElement(jsonArraytags.get(i));
           };
         }
       }
@@ -476,8 +477,9 @@ public class Pet {
 
            @Override
            public Pet read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              Pet instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/PetWithRequiredTags.java

@@ -390,27 +390,28 @@ public class PetWithRequiredTags {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to PetWithRequiredTags
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to PetWithRequiredTags
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!PetWithRequiredTags.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!PetWithRequiredTags.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in PetWithRequiredTags is not found in the empty JSON string", PetWithRequiredTags.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : PetWithRequiredTags.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       // validate the optional field `category`
       if (jsonObj.get("category") != null && !jsonObj.get("category").isJsonNull()) {
-        Category.validateJsonObject(jsonObj.getAsJsonObject("category"));
+        Category.validateJsonElement(jsonObj.get("category"));
       }
       if (!jsonObj.get("name").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `name` to be a primitive type in the JSON string but got `%s`", jsonObj.get("name").toString()));
@@ -429,7 +430,7 @@ public class PetWithRequiredTags {
       JsonArray jsonArraytags = jsonObj.getAsJsonArray("tags");
       // validate the required field `tags` (array)
       for (int i = 0; i < jsonArraytags.size(); i++) {
-        Tag.validateJsonObject(jsonArraytags.get(i).getAsJsonObject());
+        Tag.validateJsonElement(jsonArraytags.get(i));
       };
       if ((jsonObj.get("status") != null && !jsonObj.get("status").isJsonNull()) && !jsonObj.get("status").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `status` to be a primitive type in the JSON string but got `%s`", jsonObj.get("status").toString()));
@@ -473,8 +474,9 @@ public class PetWithRequiredTags {
 
            @Override
            public PetWithRequiredTags read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              PetWithRequiredTags instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Pig.java

@@ -34,6 +34,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import com.google.gson.Gson;
@@ -53,6 +54,7 @@ import com.google.gson.JsonSerializationContext;
 import com.google.gson.JsonSerializer;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
+import com.google.gson.JsonArray;
 import com.google.gson.JsonParseException;
 
 import org.openapitools.client.JSON;
@@ -82,25 +84,25 @@ public class Pig extends AbstractOpenApiSchema {
 
                     // check if the actual instance is of the type `BasquePig`
                     if (value.getActualInstance() instanceof BasquePig) {
-                        JsonObject obj = adapterBasquePig.toJsonTree((BasquePig)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
+                      JsonElement element = adapterBasquePig.toJsonTree((BasquePig)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
                     }
-
                     // check if the actual instance is of the type `DanishPig`
                     if (value.getActualInstance() instanceof DanishPig) {
-                        JsonObject obj = adapterDanishPig.toJsonTree((DanishPig)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
+                      JsonElement element = adapterDanishPig.toJsonTree((DanishPig)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
                     }
-
                     throw new IOException("Failed to serialize as the type doesn't match oneOf schemas: BasquePig, DanishPig");
                 }
 
                 @Override
                 public Pig read(JsonReader in) throws IOException {
                     Object deserialized = null;
-                    JsonObject jsonObject = elementAdapter.read(in).getAsJsonObject();
+                    JsonElement jsonElement = elementAdapter.read(in);
+
+                    JsonObject jsonObject = jsonElement.getAsJsonObject();
 
                     // use discriminator value for faster oneOf lookup
                     Pig newPig = new Pig();
@@ -128,37 +130,36 @@ public class Pig extends AbstractOpenApiSchema {
 
                     // deserialize BasquePig
                     try {
-                        // validate the JSON object to see if any exception is thrown
-                        BasquePig.validateJsonObject(jsonObject);
-                        actualAdapter = adapterBasquePig;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'BasquePig'");
+                      // validate the JSON object to see if any exception is thrown
+                      BasquePig.validateJsonElement(jsonElement);
+                      actualAdapter = adapterBasquePig;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'BasquePig'");
                     } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for BasquePig failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'BasquePig'", e);
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for BasquePig failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'BasquePig'", e);
                     }
-
                     // deserialize DanishPig
                     try {
-                        // validate the JSON object to see if any exception is thrown
-                        DanishPig.validateJsonObject(jsonObject);
-                        actualAdapter = adapterDanishPig;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'DanishPig'");
+                      // validate the JSON object to see if any exception is thrown
+                      DanishPig.validateJsonElement(jsonElement);
+                      actualAdapter = adapterDanishPig;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'DanishPig'");
                     } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for DanishPig failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'DanishPig'", e);
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for DanishPig failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'DanishPig'", e);
                     }
 
                     if (match == 1) {
                         Pig ret = new Pig();
-                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonObject));
+                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonElement));
                         return ret;
                     }
 
-                    throw new IOException(String.format("Failed deserialization for Pig: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonObject.toString()));
+                    throw new IOException(String.format("Failed deserialization for Pig: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonElement.toString()));
                 }
             }.nullSafe();
         }
@@ -235,7 +236,6 @@ public class Pig extends AbstractOpenApiSchema {
     public BasquePig getBasquePig() throws ClassCastException {
         return (BasquePig)super.getActualInstance();
     }
-
     /**
      * Get the actual instance of `DanishPig`. If the actual instance is not `DanishPig`,
      * the ClassCastException will be thrown.
@@ -247,20 +247,19 @@ public class Pig extends AbstractOpenApiSchema {
         return (DanishPig)super.getActualInstance();
     }
 
-
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Pig
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Pig
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
     // validate oneOf schemas one by one
     int validCount = 0;
     ArrayList<String> errorMessages = new ArrayList<>();
     // validate the json string with BasquePig
     try {
-      BasquePig.validateJsonObject(jsonObj);
+      BasquePig.validateJsonElement(jsonElement);
       validCount++;
     } catch (Exception e) {
       errorMessages.add(String.format("Deserialization for BasquePig failed with `%s`.", e.getMessage()));
@@ -268,14 +267,14 @@ public class Pig extends AbstractOpenApiSchema {
     }
     // validate the json string with DanishPig
     try {
-      DanishPig.validateJsonObject(jsonObj);
+      DanishPig.validateJsonElement(jsonElement);
       validCount++;
     } catch (Exception e) {
       errorMessages.add(String.format("Deserialization for DanishPig failed with `%s`.", e.getMessage()));
       // continue to the next one
     }
     if (validCount != 1) {
-      throw new IOException(String.format("The JSON string is invalid for Pig with oneOf schemas: BasquePig, DanishPig. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonObj.toString()));
+      throw new IOException(String.format("The JSON string is invalid for Pig with oneOf schemas: BasquePig, DanishPig. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonElement.toString()));
     }
   }
 

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Quadrilateral.java

@@ -34,6 +34,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import com.google.gson.Gson;
@@ -53,6 +54,7 @@ import com.google.gson.JsonSerializationContext;
 import com.google.gson.JsonSerializer;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
+import com.google.gson.JsonArray;
 import com.google.gson.JsonParseException;
 
 import org.openapitools.client.JSON;
@@ -69,8 +71,8 @@ public class Quadrilateral extends AbstractOpenApiSchema {
                 return null; // this class only serializes 'Quadrilateral' and its subtypes
             }
             final TypeAdapter<JsonElement> elementAdapter = gson.getAdapter(JsonElement.class);
-            final TypeAdapter<ComplexQuadrilateral> adapterComplexQuadrilateral = gson.getDelegateAdapter(this, TypeToken.get(ComplexQuadrilateral.class));
             final TypeAdapter<SimpleQuadrilateral> adapterSimpleQuadrilateral = gson.getDelegateAdapter(this, TypeToken.get(SimpleQuadrilateral.class));
+            final TypeAdapter<ComplexQuadrilateral> adapterComplexQuadrilateral = gson.getDelegateAdapter(this, TypeToken.get(ComplexQuadrilateral.class));
 
             return (TypeAdapter<T>) new TypeAdapter<Quadrilateral>() {
                 @Override
@@ -80,27 +82,27 @@ public class Quadrilateral extends AbstractOpenApiSchema {
                         return;
                     }
 
-                    // check if the actual instance is of the type `ComplexQuadrilateral`
-                    if (value.getActualInstance() instanceof ComplexQuadrilateral) {
-                        JsonObject obj = adapterComplexQuadrilateral.toJsonTree((ComplexQuadrilateral)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
-                    }
-
                     // check if the actual instance is of the type `SimpleQuadrilateral`
                     if (value.getActualInstance() instanceof SimpleQuadrilateral) {
-                        JsonObject obj = adapterSimpleQuadrilateral.toJsonTree((SimpleQuadrilateral)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
+                      JsonElement element = adapterSimpleQuadrilateral.toJsonTree((SimpleQuadrilateral)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
+                    }
+                    // check if the actual instance is of the type `ComplexQuadrilateral`
+                    if (value.getActualInstance() instanceof ComplexQuadrilateral) {
+                      JsonElement element = adapterComplexQuadrilateral.toJsonTree((ComplexQuadrilateral)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
                     }
-
                     throw new IOException("Failed to serialize as the type doesn't match oneOf schemas: ComplexQuadrilateral, SimpleQuadrilateral");
                 }
 
                 @Override
                 public Quadrilateral read(JsonReader in) throws IOException {
                     Object deserialized = null;
-                    JsonObject jsonObject = elementAdapter.read(in).getAsJsonObject();
+                    JsonElement jsonElement = elementAdapter.read(in);
+
+                    JsonObject jsonObject = jsonElement.getAsJsonObject();
 
                     // use discriminator value for faster oneOf lookup
                     Quadrilateral newQuadrilateral = new Quadrilateral();
@@ -126,39 +128,38 @@ public class Quadrilateral extends AbstractOpenApiSchema {
                     ArrayList<String> errorMessages = new ArrayList<>();
                     TypeAdapter actualAdapter = elementAdapter;
 
-                    // deserialize ComplexQuadrilateral
-                    try {
-                        // validate the JSON object to see if any exception is thrown
-                        ComplexQuadrilateral.validateJsonObject(jsonObject);
-                        actualAdapter = adapterComplexQuadrilateral;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'ComplexQuadrilateral'");
-                    } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for ComplexQuadrilateral failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'ComplexQuadrilateral'", e);
-                    }
-
                     // deserialize SimpleQuadrilateral
                     try {
-                        // validate the JSON object to see if any exception is thrown
-                        SimpleQuadrilateral.validateJsonObject(jsonObject);
-                        actualAdapter = adapterSimpleQuadrilateral;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'SimpleQuadrilateral'");
+                      // validate the JSON object to see if any exception is thrown
+                      SimpleQuadrilateral.validateJsonElement(jsonElement);
+                      actualAdapter = adapterSimpleQuadrilateral;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'SimpleQuadrilateral'");
                     } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for SimpleQuadrilateral failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'SimpleQuadrilateral'", e);
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for SimpleQuadrilateral failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'SimpleQuadrilateral'", e);
+                    }
+                    // deserialize ComplexQuadrilateral
+                    try {
+                      // validate the JSON object to see if any exception is thrown
+                      ComplexQuadrilateral.validateJsonElement(jsonElement);
+                      actualAdapter = adapterComplexQuadrilateral;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'ComplexQuadrilateral'");
+                    } catch (Exception e) {
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for ComplexQuadrilateral failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'ComplexQuadrilateral'", e);
                     }
 
                     if (match == 1) {
                         Quadrilateral ret = new Quadrilateral();
-                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonObject));
+                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonElement));
                         return ret;
                     }
 
-                    throw new IOException(String.format("Failed deserialization for Quadrilateral: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonObject.toString()));
+                    throw new IOException(String.format("Failed deserialization for Quadrilateral: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonElement.toString()));
                 }
             }.nullSafe();
         }
@@ -182,8 +183,8 @@ public class Quadrilateral extends AbstractOpenApiSchema {
     }
 
     static {
-        schemas.put("ComplexQuadrilateral", ComplexQuadrilateral.class);
         schemas.put("SimpleQuadrilateral", SimpleQuadrilateral.class);
+        schemas.put("ComplexQuadrilateral", ComplexQuadrilateral.class);
     }
 
     @Override
@@ -201,12 +202,12 @@ public class Quadrilateral extends AbstractOpenApiSchema {
      */
     @Override
     public void setActualInstance(Object instance) {
-        if (instance instanceof ComplexQuadrilateral) {
+        if (instance instanceof SimpleQuadrilateral) {
             super.setActualInstance(instance);
             return;
         }
 
-        if (instance instanceof SimpleQuadrilateral) {
+        if (instance instanceof ComplexQuadrilateral) {
             super.setActualInstance(instance);
             return;
         }
@@ -225,6 +226,16 @@ public class Quadrilateral extends AbstractOpenApiSchema {
         return super.getActualInstance();
     }
 
+    /**
+     * Get the actual instance of `SimpleQuadrilateral`. If the actual instance is not `SimpleQuadrilateral`,
+     * the ClassCastException will be thrown.
+     *
+     * @return The actual instance of `SimpleQuadrilateral`
+     * @throws ClassCastException if the instance is not `SimpleQuadrilateral`
+     */
+    public SimpleQuadrilateral getSimpleQuadrilateral() throws ClassCastException {
+        return (SimpleQuadrilateral)super.getActualInstance();
+    }
     /**
      * Get the actual instance of `ComplexQuadrilateral`. If the actual instance is not `ComplexQuadrilateral`,
      * the ClassCastException will be thrown.
@@ -236,46 +247,34 @@ public class Quadrilateral extends AbstractOpenApiSchema {
         return (ComplexQuadrilateral)super.getActualInstance();
     }
 
-    /**
-     * Get the actual instance of `SimpleQuadrilateral`. If the actual instance is not `SimpleQuadrilateral`,
-     * the ClassCastException will be thrown.
-     *
-     * @return The actual instance of `SimpleQuadrilateral`
-     * @throws ClassCastException if the instance is not `SimpleQuadrilateral`
-     */
-    public SimpleQuadrilateral getSimpleQuadrilateral() throws ClassCastException {
-        return (SimpleQuadrilateral)super.getActualInstance();
-    }
-
-
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Quadrilateral
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Quadrilateral
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
     // validate oneOf schemas one by one
     int validCount = 0;
     ArrayList<String> errorMessages = new ArrayList<>();
-    // validate the json string with ComplexQuadrilateral
-    try {
-      ComplexQuadrilateral.validateJsonObject(jsonObj);
-      validCount++;
-    } catch (Exception e) {
-      errorMessages.add(String.format("Deserialization for ComplexQuadrilateral failed with `%s`.", e.getMessage()));
-      // continue to the next one
-    }
     // validate the json string with SimpleQuadrilateral
     try {
-      SimpleQuadrilateral.validateJsonObject(jsonObj);
+      SimpleQuadrilateral.validateJsonElement(jsonElement);
       validCount++;
     } catch (Exception e) {
       errorMessages.add(String.format("Deserialization for SimpleQuadrilateral failed with `%s`.", e.getMessage()));
       // continue to the next one
     }
+    // validate the json string with ComplexQuadrilateral
+    try {
+      ComplexQuadrilateral.validateJsonElement(jsonElement);
+      validCount++;
+    } catch (Exception e) {
+      errorMessages.add(String.format("Deserialization for ComplexQuadrilateral failed with `%s`.", e.getMessage()));
+      // continue to the next one
+    }
     if (validCount != 1) {
-      throw new IOException(String.format("The JSON string is invalid for Quadrilateral with oneOf schemas: ComplexQuadrilateral, SimpleQuadrilateral. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonObj.toString()));
+      throw new IOException(String.format("The JSON string is invalid for Quadrilateral with oneOf schemas: ComplexQuadrilateral, SimpleQuadrilateral. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonElement.toString()));
     }
   }
 

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/QuadrilateralInterface.java

@@ -179,24 +179,25 @@ public class QuadrilateralInterface {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to QuadrilateralInterface
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to QuadrilateralInterface
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!QuadrilateralInterface.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!QuadrilateralInterface.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in QuadrilateralInterface is not found in the empty JSON string", QuadrilateralInterface.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : QuadrilateralInterface.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if (!jsonObj.get("quadrilateralType").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `quadrilateralType` to be a primitive type in the JSON string but got `%s`", jsonObj.get("quadrilateralType").toString()));
       }
@@ -239,8 +240,9 @@ public class QuadrilateralInterface {
 
            @Override
            public QuadrilateralInterface read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              QuadrilateralInterface instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ReadOnlyFirst.java

@@ -205,17 +205,18 @@ public class ReadOnlyFirst {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ReadOnlyFirst
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ReadOnlyFirst
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ReadOnlyFirst.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ReadOnlyFirst.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ReadOnlyFirst is not found in the empty JSON string", ReadOnlyFirst.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("bar") != null && !jsonObj.get("bar").isJsonNull()) && !jsonObj.get("bar").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `bar` to be a primitive type in the JSON string but got `%s`", jsonObj.get("bar").toString()));
       }
@@ -261,8 +262,9 @@ public class ReadOnlyFirst {
 
            @Override
            public ReadOnlyFirst read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ReadOnlyFirst instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Scalar.java

@@ -0,0 +1,332 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import java.math.BigDecimal;
+
+
+
+import java.io.IOException;
+import java.lang.reflect.Type;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonParseException;
+import com.google.gson.TypeAdapter;
+import com.google.gson.TypeAdapterFactory;
+import com.google.gson.reflect.TypeToken;
+import com.google.gson.JsonPrimitive;
+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 com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonSerializationContext;
+import com.google.gson.JsonSerializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonParseException;
+
+import org.openapitools.client.JSON;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Scalar extends AbstractOpenApiSchema {
+    private static final Logger log = Logger.getLogger(Scalar.class.getName());
+
+    public static class CustomTypeAdapterFactory implements TypeAdapterFactory {
+        @SuppressWarnings("unchecked")
+        @Override
+        public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
+            if (!Scalar.class.isAssignableFrom(type.getRawType())) {
+                return null; // this class only serializes 'Scalar' and its subtypes
+            }
+            final TypeAdapter<JsonElement> elementAdapter = gson.getAdapter(JsonElement.class);
+            final TypeAdapter<String> adapterString = gson.getDelegateAdapter(this, TypeToken.get(String.class));
+            final TypeAdapter<BigDecimal> adapterBigDecimal = gson.getDelegateAdapter(this, TypeToken.get(BigDecimal.class));
+            final TypeAdapter<Boolean> adapterBoolean = gson.getDelegateAdapter(this, TypeToken.get(Boolean.class));
+
+            return (TypeAdapter<T>) new TypeAdapter<Scalar>() {
+                @Override
+                public void write(JsonWriter out, Scalar value) throws IOException {
+                    if (value == null || value.getActualInstance() == null) {
+                        elementAdapter.write(out, null);
+                        return;
+                    }
+
+                    // check if the actual instance is of the type `String`
+                    if (value.getActualInstance() instanceof String) {
+                      JsonPrimitive primitive = adapterString.toJsonTree((String)value.getActualInstance()).getAsJsonPrimitive();
+                      elementAdapter.write(out, primitive);
+                      return;
+                    }
+                    // check if the actual instance is of the type `BigDecimal`
+                    if (value.getActualInstance() instanceof BigDecimal) {
+                      JsonPrimitive primitive = adapterBigDecimal.toJsonTree((BigDecimal)value.getActualInstance()).getAsJsonPrimitive();
+                      elementAdapter.write(out, primitive);
+                      return;
+                    }
+                    // check if the actual instance is of the type `Boolean`
+                    if (value.getActualInstance() instanceof Boolean) {
+                      JsonPrimitive primitive = adapterBoolean.toJsonTree((Boolean)value.getActualInstance()).getAsJsonPrimitive();
+                      elementAdapter.write(out, primitive);
+                      return;
+                    }
+                    throw new IOException("Failed to serialize as the type doesn't match oneOf schemas: BigDecimal, Boolean, String");
+                }
+
+                @Override
+                public Scalar read(JsonReader in) throws IOException {
+                    Object deserialized = null;
+                    JsonElement jsonElement = elementAdapter.read(in);
+
+                    int match = 0;
+                    ArrayList<String> errorMessages = new ArrayList<>();
+                    TypeAdapter actualAdapter = elementAdapter;
+
+                    // deserialize String
+                    try {
+                      // validate the JSON object to see if any exception is thrown
+                      if(!jsonElement.getAsJsonPrimitive().isString()) {
+                        throw new IllegalArgumentException(String.format("Expected json element to be of type String in the JSON string but got `%s`", jsonElement.toString()));
+                      }
+                      actualAdapter = adapterString;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'String'");
+                    } catch (Exception e) {
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for String failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'String'", e);
+                    }
+                    // deserialize BigDecimal
+                    try {
+                      // validate the JSON object to see if any exception is thrown
+                      if(!jsonElement.getAsJsonPrimitive().isNumber()) {
+                        throw new IllegalArgumentException(String.format("Expected json element to be of type Number in the JSON string but got `%s`", jsonElement.toString()));
+                      }
+                      actualAdapter = adapterBigDecimal;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'BigDecimal'");
+                    } catch (Exception e) {
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for BigDecimal failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'BigDecimal'", e);
+                    }
+                    // deserialize Boolean
+                    try {
+                      // validate the JSON object to see if any exception is thrown
+                      if(!jsonElement.getAsJsonPrimitive().isBoolean()) {
+                        throw new IllegalArgumentException(String.format("Expected json element to be of type Boolean in the JSON string but got `%s`", jsonElement.toString()));
+                      }
+                      actualAdapter = adapterBoolean;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'Boolean'");
+                    } catch (Exception e) {
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for Boolean failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'Boolean'", e);
+                    }
+
+                    if (match == 1) {
+                        Scalar ret = new Scalar();
+                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonElement));
+                        return ret;
+                    }
+
+                    throw new IOException(String.format("Failed deserialization for Scalar: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonElement.toString()));
+                }
+            }.nullSafe();
+        }
+    }
+
+    // store a list of schema names defined in oneOf
+    public static final Map<String, Class<?>> schemas = new HashMap<String, Class<?>>();
+
+    public Scalar() {
+        super("oneOf", Boolean.FALSE);
+    }
+
+    public Scalar(BigDecimal o) {
+        super("oneOf", Boolean.FALSE);
+        setActualInstance(o);
+    }
+
+    public Scalar(Boolean o) {
+        super("oneOf", Boolean.FALSE);
+        setActualInstance(o);
+    }
+
+    public Scalar(String o) {
+        super("oneOf", Boolean.FALSE);
+        setActualInstance(o);
+    }
+
+    static {
+        schemas.put("String", String.class);
+        schemas.put("BigDecimal", BigDecimal.class);
+        schemas.put("Boolean", Boolean.class);
+    }
+
+    @Override
+    public Map<String, Class<?>> getSchemas() {
+        return Scalar.schemas;
+    }
+
+    /**
+     * Set the instance that matches the oneOf child schema, check
+     * the instance parameter is valid against the oneOf child schemas:
+     * BigDecimal, Boolean, String
+     *
+     * It could be an instance of the 'oneOf' schemas.
+     * The oneOf child schemas may themselves be a composed schema (allOf, anyOf, oneOf).
+     */
+    @Override
+    public void setActualInstance(Object instance) {
+        if (instance instanceof String) {
+            super.setActualInstance(instance);
+            return;
+        }
+
+        if (instance instanceof BigDecimal) {
+            super.setActualInstance(instance);
+            return;
+        }
+
+        if (instance instanceof Boolean) {
+            super.setActualInstance(instance);
+            return;
+        }
+
+        throw new RuntimeException("Invalid instance type. Must be BigDecimal, Boolean, String");
+    }
+
+    /**
+     * Get the actual instance, which can be the following:
+     * BigDecimal, Boolean, String
+     *
+     * @return The actual instance (BigDecimal, Boolean, String)
+     */
+    @Override
+    public Object getActualInstance() {
+        return super.getActualInstance();
+    }
+
+    /**
+     * Get the actual instance of `String`. If the actual instance is not `String`,
+     * the ClassCastException will be thrown.
+     *
+     * @return The actual instance of `String`
+     * @throws ClassCastException if the instance is not `String`
+     */
+    public String getString() throws ClassCastException {
+        return (String)super.getActualInstance();
+    }
+    /**
+     * Get the actual instance of `BigDecimal`. If the actual instance is not `BigDecimal`,
+     * the ClassCastException will be thrown.
+     *
+     * @return The actual instance of `BigDecimal`
+     * @throws ClassCastException if the instance is not `BigDecimal`
+     */
+    public BigDecimal getBigDecimal() throws ClassCastException {
+        return (BigDecimal)super.getActualInstance();
+    }
+    /**
+     * Get the actual instance of `Boolean`. If the actual instance is not `Boolean`,
+     * the ClassCastException will be thrown.
+     *
+     * @return The actual instance of `Boolean`
+     * @throws ClassCastException if the instance is not `Boolean`
+     */
+    public Boolean getBoolean() throws ClassCastException {
+        return (Boolean)super.getActualInstance();
+    }
+
+ /**
+  * Validates the JSON Element and throws an exception if issues found
+  *
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Scalar
+  */
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+    // validate oneOf schemas one by one
+    int validCount = 0;
+    ArrayList<String> errorMessages = new ArrayList<>();
+    // validate the json string with String
+    try {
+      if(!jsonElement.getAsJsonPrimitive().isString()) {
+        throw new IllegalArgumentException(String.format("Expected json element to be of type String in the JSON string but got `%s`", jsonElement.toString()));
+      }
+      validCount++;
+    } catch (Exception e) {
+      errorMessages.add(String.format("Deserialization for String failed with `%s`.", e.getMessage()));
+      // continue to the next one
+    }
+    // validate the json string with BigDecimal
+    try {
+      if(!jsonElement.getAsJsonPrimitive().isNumber()) {
+        throw new IllegalArgumentException(String.format("Expected json element to be of type Number in the JSON string but got `%s`", jsonElement.toString()));
+      }
+      validCount++;
+    } catch (Exception e) {
+      errorMessages.add(String.format("Deserialization for BigDecimal failed with `%s`.", e.getMessage()));
+      // continue to the next one
+    }
+    // validate the json string with Boolean
+    try {
+      if(!jsonElement.getAsJsonPrimitive().isBoolean()) {
+        throw new IllegalArgumentException(String.format("Expected json element to be of type Boolean in the JSON string but got `%s`", jsonElement.toString()));
+      }
+      validCount++;
+    } catch (Exception e) {
+      errorMessages.add(String.format("Deserialization for Boolean failed with `%s`.", e.getMessage()));
+      // continue to the next one
+    }
+    if (validCount != 1) {
+      throw new IOException(String.format("The JSON string is invalid for Scalar with oneOf schemas: BigDecimal, Boolean, String. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonElement.toString()));
+    }
+  }
+
+ /**
+  * Create an instance of Scalar given an JSON string
+  *
+  * @param jsonString JSON string
+  * @return An instance of Scalar
+  * @throws IOException if the JSON string is invalid with respect to Scalar
+  */
+  public static Scalar fromJson(String jsonString) throws IOException {
+    return JSON.getGson().fromJson(jsonString, Scalar.class);
+  }
+
+ /**
+  * Convert an instance of Scalar to an JSON string
+  *
+  * @return JSON string
+  */
+  public String toJson() {
+    return JSON.getGson().toJson(this);
+  }
+}
+

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ScaleneTriangle.java

@@ -208,24 +208,25 @@ public class ScaleneTriangle {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ScaleneTriangle
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ScaleneTriangle
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ScaleneTriangle.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ScaleneTriangle.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ScaleneTriangle is not found in the empty JSON string", ScaleneTriangle.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : ScaleneTriangle.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if (!jsonObj.get("shapeType").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `shapeType` to be a primitive type in the JSON string but got `%s`", jsonObj.get("shapeType").toString()));
       }
@@ -271,8 +272,9 @@ public class ScaleneTriangle {
 
            @Override
            public ScaleneTriangle read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ScaleneTriangle instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Shape.java

@@ -34,6 +34,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import com.google.gson.Gson;
@@ -53,6 +54,7 @@ import com.google.gson.JsonSerializationContext;
 import com.google.gson.JsonSerializer;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
+import com.google.gson.JsonArray;
 import com.google.gson.JsonParseException;
 
 import org.openapitools.client.JSON;
@@ -69,8 +71,8 @@ public class Shape extends AbstractOpenApiSchema {
                 return null; // this class only serializes 'Shape' and its subtypes
             }
             final TypeAdapter<JsonElement> elementAdapter = gson.getAdapter(JsonElement.class);
-            final TypeAdapter<Quadrilateral> adapterQuadrilateral = gson.getDelegateAdapter(this, TypeToken.get(Quadrilateral.class));
             final TypeAdapter<Triangle> adapterTriangle = gson.getDelegateAdapter(this, TypeToken.get(Triangle.class));
+            final TypeAdapter<Quadrilateral> adapterQuadrilateral = gson.getDelegateAdapter(this, TypeToken.get(Quadrilateral.class));
 
             return (TypeAdapter<T>) new TypeAdapter<Shape>() {
                 @Override
@@ -80,27 +82,27 @@ public class Shape extends AbstractOpenApiSchema {
                         return;
                     }
 
-                    // check if the actual instance is of the type `Quadrilateral`
-                    if (value.getActualInstance() instanceof Quadrilateral) {
-                        JsonObject obj = adapterQuadrilateral.toJsonTree((Quadrilateral)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
-                    }
-
                     // check if the actual instance is of the type `Triangle`
                     if (value.getActualInstance() instanceof Triangle) {
-                        JsonObject obj = adapterTriangle.toJsonTree((Triangle)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
+                      JsonElement element = adapterTriangle.toJsonTree((Triangle)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
+                    }
+                    // check if the actual instance is of the type `Quadrilateral`
+                    if (value.getActualInstance() instanceof Quadrilateral) {
+                      JsonElement element = adapterQuadrilateral.toJsonTree((Quadrilateral)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
                     }
-
                     throw new IOException("Failed to serialize as the type doesn't match oneOf schemas: Quadrilateral, Triangle");
                 }
 
                 @Override
                 public Shape read(JsonReader in) throws IOException {
                     Object deserialized = null;
-                    JsonObject jsonObject = elementAdapter.read(in).getAsJsonObject();
+                    JsonElement jsonElement = elementAdapter.read(in);
+
+                    JsonObject jsonObject = jsonElement.getAsJsonObject();
 
                     // use discriminator value for faster oneOf lookup
                     Shape newShape = new Shape();
@@ -126,39 +128,38 @@ public class Shape extends AbstractOpenApiSchema {
                     ArrayList<String> errorMessages = new ArrayList<>();
                     TypeAdapter actualAdapter = elementAdapter;
 
-                    // deserialize Quadrilateral
-                    try {
-                        // validate the JSON object to see if any exception is thrown
-                        Quadrilateral.validateJsonObject(jsonObject);
-                        actualAdapter = adapterQuadrilateral;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'Quadrilateral'");
-                    } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for Quadrilateral failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'Quadrilateral'", e);
-                    }
-
                     // deserialize Triangle
                     try {
-                        // validate the JSON object to see if any exception is thrown
-                        Triangle.validateJsonObject(jsonObject);
-                        actualAdapter = adapterTriangle;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'Triangle'");
+                      // validate the JSON object to see if any exception is thrown
+                      Triangle.validateJsonElement(jsonElement);
+                      actualAdapter = adapterTriangle;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'Triangle'");
                     } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for Triangle failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'Triangle'", e);
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for Triangle failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'Triangle'", e);
+                    }
+                    // deserialize Quadrilateral
+                    try {
+                      // validate the JSON object to see if any exception is thrown
+                      Quadrilateral.validateJsonElement(jsonElement);
+                      actualAdapter = adapterQuadrilateral;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'Quadrilateral'");
+                    } catch (Exception e) {
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for Quadrilateral failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'Quadrilateral'", e);
                     }
 
                     if (match == 1) {
                         Shape ret = new Shape();
-                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonObject));
+                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonElement));
                         return ret;
                     }
 
-                    throw new IOException(String.format("Failed deserialization for Shape: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonObject.toString()));
+                    throw new IOException(String.format("Failed deserialization for Shape: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonElement.toString()));
                 }
             }.nullSafe();
         }
@@ -182,8 +183,8 @@ public class Shape extends AbstractOpenApiSchema {
     }
 
     static {
-        schemas.put("Quadrilateral", Quadrilateral.class);
         schemas.put("Triangle", Triangle.class);
+        schemas.put("Quadrilateral", Quadrilateral.class);
     }
 
     @Override
@@ -201,12 +202,12 @@ public class Shape extends AbstractOpenApiSchema {
      */
     @Override
     public void setActualInstance(Object instance) {
-        if (instance instanceof Quadrilateral) {
+        if (instance instanceof Triangle) {
             super.setActualInstance(instance);
             return;
         }
 
-        if (instance instanceof Triangle) {
+        if (instance instanceof Quadrilateral) {
             super.setActualInstance(instance);
             return;
         }
@@ -225,6 +226,16 @@ public class Shape extends AbstractOpenApiSchema {
         return super.getActualInstance();
     }
 
+    /**
+     * Get the actual instance of `Triangle`. If the actual instance is not `Triangle`,
+     * the ClassCastException will be thrown.
+     *
+     * @return The actual instance of `Triangle`
+     * @throws ClassCastException if the instance is not `Triangle`
+     */
+    public Triangle getTriangle() throws ClassCastException {
+        return (Triangle)super.getActualInstance();
+    }
     /**
      * Get the actual instance of `Quadrilateral`. If the actual instance is not `Quadrilateral`,
      * the ClassCastException will be thrown.
@@ -236,46 +247,34 @@ public class Shape extends AbstractOpenApiSchema {
         return (Quadrilateral)super.getActualInstance();
     }
 
-    /**
-     * Get the actual instance of `Triangle`. If the actual instance is not `Triangle`,
-     * the ClassCastException will be thrown.
-     *
-     * @return The actual instance of `Triangle`
-     * @throws ClassCastException if the instance is not `Triangle`
-     */
-    public Triangle getTriangle() throws ClassCastException {
-        return (Triangle)super.getActualInstance();
-    }
-
-
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Shape
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Shape
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
     // validate oneOf schemas one by one
     int validCount = 0;
     ArrayList<String> errorMessages = new ArrayList<>();
-    // validate the json string with Quadrilateral
-    try {
-      Quadrilateral.validateJsonObject(jsonObj);
-      validCount++;
-    } catch (Exception e) {
-      errorMessages.add(String.format("Deserialization for Quadrilateral failed with `%s`.", e.getMessage()));
-      // continue to the next one
-    }
     // validate the json string with Triangle
     try {
-      Triangle.validateJsonObject(jsonObj);
+      Triangle.validateJsonElement(jsonElement);
       validCount++;
     } catch (Exception e) {
       errorMessages.add(String.format("Deserialization for Triangle failed with `%s`.", e.getMessage()));
       // continue to the next one
     }
+    // validate the json string with Quadrilateral
+    try {
+      Quadrilateral.validateJsonElement(jsonElement);
+      validCount++;
+    } catch (Exception e) {
+      errorMessages.add(String.format("Deserialization for Quadrilateral failed with `%s`.", e.getMessage()));
+      // continue to the next one
+    }
     if (validCount != 1) {
-      throw new IOException(String.format("The JSON string is invalid for Shape with oneOf schemas: Quadrilateral, Triangle. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonObj.toString()));
+      throw new IOException(String.format("The JSON string is invalid for Shape with oneOf schemas: Quadrilateral, Triangle. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonElement.toString()));
     }
   }
 

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ShapeInterface.java

@@ -179,24 +179,25 @@ public class ShapeInterface {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ShapeInterface
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ShapeInterface
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!ShapeInterface.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!ShapeInterface.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in ShapeInterface is not found in the empty JSON string", ShapeInterface.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : ShapeInterface.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if (!jsonObj.get("shapeType").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `shapeType` to be a primitive type in the JSON string but got `%s`", jsonObj.get("shapeType").toString()));
       }
@@ -239,8 +240,9 @@ public class ShapeInterface {
 
            @Override
            public ShapeInterface read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              ShapeInterface instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/ShapeOrNull.java

@@ -34,6 +34,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import com.google.gson.Gson;
@@ -53,6 +54,7 @@ import com.google.gson.JsonSerializationContext;
 import com.google.gson.JsonSerializer;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
+import com.google.gson.JsonArray;
 import com.google.gson.JsonParseException;
 
 import org.openapitools.client.JSON;
@@ -69,8 +71,8 @@ public class ShapeOrNull extends AbstractOpenApiSchema {
                 return null; // this class only serializes 'ShapeOrNull' and its subtypes
             }
             final TypeAdapter<JsonElement> elementAdapter = gson.getAdapter(JsonElement.class);
-            final TypeAdapter<Quadrilateral> adapterQuadrilateral = gson.getDelegateAdapter(this, TypeToken.get(Quadrilateral.class));
             final TypeAdapter<Triangle> adapterTriangle = gson.getDelegateAdapter(this, TypeToken.get(Triangle.class));
+            final TypeAdapter<Quadrilateral> adapterQuadrilateral = gson.getDelegateAdapter(this, TypeToken.get(Quadrilateral.class));
 
             return (TypeAdapter<T>) new TypeAdapter<ShapeOrNull>() {
                 @Override
@@ -80,27 +82,27 @@ public class ShapeOrNull extends AbstractOpenApiSchema {
                         return;
                     }
 
-                    // check if the actual instance is of the type `Quadrilateral`
-                    if (value.getActualInstance() instanceof Quadrilateral) {
-                        JsonObject obj = adapterQuadrilateral.toJsonTree((Quadrilateral)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
-                    }
-
                     // check if the actual instance is of the type `Triangle`
                     if (value.getActualInstance() instanceof Triangle) {
-                        JsonObject obj = adapterTriangle.toJsonTree((Triangle)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
+                      JsonElement element = adapterTriangle.toJsonTree((Triangle)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
+                    }
+                    // check if the actual instance is of the type `Quadrilateral`
+                    if (value.getActualInstance() instanceof Quadrilateral) {
+                      JsonElement element = adapterQuadrilateral.toJsonTree((Quadrilateral)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
                     }
-
                     throw new IOException("Failed to serialize as the type doesn't match oneOf schemas: Quadrilateral, Triangle");
                 }
 
                 @Override
                 public ShapeOrNull read(JsonReader in) throws IOException {
                     Object deserialized = null;
-                    JsonObject jsonObject = elementAdapter.read(in).getAsJsonObject();
+                    JsonElement jsonElement = elementAdapter.read(in);
+
+                    JsonObject jsonObject = jsonElement.getAsJsonObject();
 
                     // use discriminator value for faster oneOf lookup
                     ShapeOrNull newShapeOrNull = new ShapeOrNull();
@@ -126,39 +128,38 @@ public class ShapeOrNull extends AbstractOpenApiSchema {
                     ArrayList<String> errorMessages = new ArrayList<>();
                     TypeAdapter actualAdapter = elementAdapter;
 
-                    // deserialize Quadrilateral
-                    try {
-                        // validate the JSON object to see if any exception is thrown
-                        Quadrilateral.validateJsonObject(jsonObject);
-                        actualAdapter = adapterQuadrilateral;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'Quadrilateral'");
-                    } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for Quadrilateral failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'Quadrilateral'", e);
-                    }
-
                     // deserialize Triangle
                     try {
-                        // validate the JSON object to see if any exception is thrown
-                        Triangle.validateJsonObject(jsonObject);
-                        actualAdapter = adapterTriangle;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'Triangle'");
+                      // validate the JSON object to see if any exception is thrown
+                      Triangle.validateJsonElement(jsonElement);
+                      actualAdapter = adapterTriangle;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'Triangle'");
                     } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for Triangle failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'Triangle'", e);
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for Triangle failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'Triangle'", e);
+                    }
+                    // deserialize Quadrilateral
+                    try {
+                      // validate the JSON object to see if any exception is thrown
+                      Quadrilateral.validateJsonElement(jsonElement);
+                      actualAdapter = adapterQuadrilateral;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'Quadrilateral'");
+                    } catch (Exception e) {
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for Quadrilateral failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'Quadrilateral'", e);
                     }
 
                     if (match == 1) {
                         ShapeOrNull ret = new ShapeOrNull();
-                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonObject));
+                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonElement));
                         return ret;
                     }
 
-                    throw new IOException(String.format("Failed deserialization for ShapeOrNull: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonObject.toString()));
+                    throw new IOException(String.format("Failed deserialization for ShapeOrNull: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonElement.toString()));
                 }
             }.nullSafe();
         }
@@ -182,8 +183,8 @@ public class ShapeOrNull extends AbstractOpenApiSchema {
     }
 
     static {
-        schemas.put("Quadrilateral", Quadrilateral.class);
         schemas.put("Triangle", Triangle.class);
+        schemas.put("Quadrilateral", Quadrilateral.class);
     }
 
     @Override
@@ -206,12 +207,12 @@ public class ShapeOrNull extends AbstractOpenApiSchema {
            return;
         }
 
-        if (instance instanceof Quadrilateral) {
+        if (instance instanceof Triangle) {
             super.setActualInstance(instance);
             return;
         }
 
-        if (instance instanceof Triangle) {
+        if (instance instanceof Quadrilateral) {
             super.setActualInstance(instance);
             return;
         }
@@ -230,6 +231,16 @@ public class ShapeOrNull extends AbstractOpenApiSchema {
         return super.getActualInstance();
     }
 
+    /**
+     * Get the actual instance of `Triangle`. If the actual instance is not `Triangle`,
+     * the ClassCastException will be thrown.
+     *
+     * @return The actual instance of `Triangle`
+     * @throws ClassCastException if the instance is not `Triangle`
+     */
+    public Triangle getTriangle() throws ClassCastException {
+        return (Triangle)super.getActualInstance();
+    }
     /**
      * Get the actual instance of `Quadrilateral`. If the actual instance is not `Quadrilateral`,
      * the ClassCastException will be thrown.
@@ -241,46 +252,34 @@ public class ShapeOrNull extends AbstractOpenApiSchema {
         return (Quadrilateral)super.getActualInstance();
     }
 
-    /**
-     * Get the actual instance of `Triangle`. If the actual instance is not `Triangle`,
-     * the ClassCastException will be thrown.
-     *
-     * @return The actual instance of `Triangle`
-     * @throws ClassCastException if the instance is not `Triangle`
-     */
-    public Triangle getTriangle() throws ClassCastException {
-        return (Triangle)super.getActualInstance();
-    }
-
-
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to ShapeOrNull
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to ShapeOrNull
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
     // validate oneOf schemas one by one
     int validCount = 0;
     ArrayList<String> errorMessages = new ArrayList<>();
-    // validate the json string with Quadrilateral
-    try {
-      Quadrilateral.validateJsonObject(jsonObj);
-      validCount++;
-    } catch (Exception e) {
-      errorMessages.add(String.format("Deserialization for Quadrilateral failed with `%s`.", e.getMessage()));
-      // continue to the next one
-    }
     // validate the json string with Triangle
     try {
-      Triangle.validateJsonObject(jsonObj);
+      Triangle.validateJsonElement(jsonElement);
       validCount++;
     } catch (Exception e) {
       errorMessages.add(String.format("Deserialization for Triangle failed with `%s`.", e.getMessage()));
       // continue to the next one
     }
+    // validate the json string with Quadrilateral
+    try {
+      Quadrilateral.validateJsonElement(jsonElement);
+      validCount++;
+    } catch (Exception e) {
+      errorMessages.add(String.format("Deserialization for Quadrilateral failed with `%s`.", e.getMessage()));
+      // continue to the next one
+    }
     if (validCount != 1) {
-      throw new IOException(String.format("The JSON string is invalid for ShapeOrNull with oneOf schemas: Quadrilateral, Triangle. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonObj.toString()));
+      throw new IOException(String.format("The JSON string is invalid for ShapeOrNull with oneOf schemas: Quadrilateral, Triangle. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonElement.toString()));
     }
   }
 

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/SimpleQuadrilateral.java

@@ -208,24 +208,25 @@ public class SimpleQuadrilateral {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to SimpleQuadrilateral
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to SimpleQuadrilateral
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!SimpleQuadrilateral.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!SimpleQuadrilateral.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in SimpleQuadrilateral is not found in the empty JSON string", SimpleQuadrilateral.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : SimpleQuadrilateral.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if (!jsonObj.get("shapeType").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `shapeType` to be a primitive type in the JSON string but got `%s`", jsonObj.get("shapeType").toString()));
       }
@@ -271,8 +272,9 @@ public class SimpleQuadrilateral {
 
            @Override
            public SimpleQuadrilateral read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              SimpleQuadrilateral instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/SpecialModelName.java

@@ -206,17 +206,18 @@ public class SpecialModelName {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to SpecialModelName
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to SpecialModelName
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!SpecialModelName.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!SpecialModelName.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in SpecialModelName is not found in the empty JSON string", SpecialModelName.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("_special_model.name_") != null && !jsonObj.get("_special_model.name_").isJsonNull()) && !jsonObj.get("_special_model.name_").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `_special_model.name_` to be a primitive type in the JSON string but got `%s`", jsonObj.get("_special_model.name_").toString()));
       }
@@ -259,8 +260,9 @@ public class SpecialModelName {
 
            @Override
            public SpecialModelName read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              SpecialModelName instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Tag.java

@@ -206,17 +206,18 @@ public class Tag {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Tag
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Tag
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!Tag.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Tag.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in Tag is not found in the empty JSON string", Tag.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("name") != null && !jsonObj.get("name").isJsonNull()) && !jsonObj.get("name").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `name` to be a primitive type in the JSON string but got `%s`", jsonObj.get("name").toString()));
       }
@@ -259,8 +260,9 @@ public class Tag {
 
            @Override
            public Tag read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              Tag instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Triangle.java

@@ -35,6 +35,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import com.google.gson.Gson;
@@ -54,6 +55,7 @@ import com.google.gson.JsonSerializationContext;
 import com.google.gson.JsonSerializer;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
+import com.google.gson.JsonArray;
 import com.google.gson.JsonParseException;
 
 import org.openapitools.client.JSON;
@@ -84,32 +86,31 @@ public class Triangle extends AbstractOpenApiSchema {
 
                     // check if the actual instance is of the type `EquilateralTriangle`
                     if (value.getActualInstance() instanceof EquilateralTriangle) {
-                        JsonObject obj = adapterEquilateralTriangle.toJsonTree((EquilateralTriangle)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
+                      JsonElement element = adapterEquilateralTriangle.toJsonTree((EquilateralTriangle)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
                     }
-
                     // check if the actual instance is of the type `IsoscelesTriangle`
                     if (value.getActualInstance() instanceof IsoscelesTriangle) {
-                        JsonObject obj = adapterIsoscelesTriangle.toJsonTree((IsoscelesTriangle)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
+                      JsonElement element = adapterIsoscelesTriangle.toJsonTree((IsoscelesTriangle)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
                     }
-
                     // check if the actual instance is of the type `ScaleneTriangle`
                     if (value.getActualInstance() instanceof ScaleneTriangle) {
-                        JsonObject obj = adapterScaleneTriangle.toJsonTree((ScaleneTriangle)value.getActualInstance()).getAsJsonObject();
-                        elementAdapter.write(out, obj);
-                        return;
+                      JsonElement element = adapterScaleneTriangle.toJsonTree((ScaleneTriangle)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
                     }
-
                     throw new IOException("Failed to serialize as the type doesn't match oneOf schemas: EquilateralTriangle, IsoscelesTriangle, ScaleneTriangle");
                 }
 
                 @Override
                 public Triangle read(JsonReader in) throws IOException {
                     Object deserialized = null;
-                    JsonObject jsonObject = elementAdapter.read(in).getAsJsonObject();
+                    JsonElement jsonElement = elementAdapter.read(in);
+
+                    JsonObject jsonObject = jsonElement.getAsJsonObject();
 
                     // use discriminator value for faster oneOf lookup
                     Triangle newTriangle = new Triangle();
@@ -141,50 +142,48 @@ public class Triangle extends AbstractOpenApiSchema {
 
                     // deserialize EquilateralTriangle
                     try {
-                        // validate the JSON object to see if any exception is thrown
-                        EquilateralTriangle.validateJsonObject(jsonObject);
-                        actualAdapter = adapterEquilateralTriangle;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'EquilateralTriangle'");
+                      // validate the JSON object to see if any exception is thrown
+                      EquilateralTriangle.validateJsonElement(jsonElement);
+                      actualAdapter = adapterEquilateralTriangle;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'EquilateralTriangle'");
                     } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for EquilateralTriangle failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'EquilateralTriangle'", e);
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for EquilateralTriangle failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'EquilateralTriangle'", e);
                     }
-
                     // deserialize IsoscelesTriangle
                     try {
-                        // validate the JSON object to see if any exception is thrown
-                        IsoscelesTriangle.validateJsonObject(jsonObject);
-                        actualAdapter = adapterIsoscelesTriangle;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'IsoscelesTriangle'");
+                      // validate the JSON object to see if any exception is thrown
+                      IsoscelesTriangle.validateJsonElement(jsonElement);
+                      actualAdapter = adapterIsoscelesTriangle;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'IsoscelesTriangle'");
                     } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for IsoscelesTriangle failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'IsoscelesTriangle'", e);
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for IsoscelesTriangle failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'IsoscelesTriangle'", e);
                     }
-
                     // deserialize ScaleneTriangle
                     try {
-                        // validate the JSON object to see if any exception is thrown
-                        ScaleneTriangle.validateJsonObject(jsonObject);
-                        actualAdapter = adapterScaleneTriangle;
-                        match++;
-                        log.log(Level.FINER, "Input data matches schema 'ScaleneTriangle'");
+                      // validate the JSON object to see if any exception is thrown
+                      ScaleneTriangle.validateJsonElement(jsonElement);
+                      actualAdapter = adapterScaleneTriangle;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'ScaleneTriangle'");
                     } catch (Exception e) {
-                        // deserialization failed, continue
-                        errorMessages.add(String.format("Deserialization for ScaleneTriangle failed with `%s`.", e.getMessage()));
-                        log.log(Level.FINER, "Input data does not match schema 'ScaleneTriangle'", e);
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for ScaleneTriangle failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'ScaleneTriangle'", e);
                     }
 
                     if (match == 1) {
                         Triangle ret = new Triangle();
-                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonObject));
+                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonElement));
                         return ret;
                     }
 
-                    throw new IOException(String.format("Failed deserialization for Triangle: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonObject.toString()));
+                    throw new IOException(String.format("Failed deserialization for Triangle: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonElement.toString()));
                 }
             }.nullSafe();
         }
@@ -272,7 +271,6 @@ public class Triangle extends AbstractOpenApiSchema {
     public EquilateralTriangle getEquilateralTriangle() throws ClassCastException {
         return (EquilateralTriangle)super.getActualInstance();
     }
-
     /**
      * Get the actual instance of `IsoscelesTriangle`. If the actual instance is not `IsoscelesTriangle`,
      * the ClassCastException will be thrown.
@@ -283,7 +281,6 @@ public class Triangle extends AbstractOpenApiSchema {
     public IsoscelesTriangle getIsoscelesTriangle() throws ClassCastException {
         return (IsoscelesTriangle)super.getActualInstance();
     }
-
     /**
      * Get the actual instance of `ScaleneTriangle`. If the actual instance is not `ScaleneTriangle`,
      * the ClassCastException will be thrown.
@@ -295,20 +292,19 @@ public class Triangle extends AbstractOpenApiSchema {
         return (ScaleneTriangle)super.getActualInstance();
     }
 
-
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Triangle
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Triangle
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
     // validate oneOf schemas one by one
     int validCount = 0;
     ArrayList<String> errorMessages = new ArrayList<>();
     // validate the json string with EquilateralTriangle
     try {
-      EquilateralTriangle.validateJsonObject(jsonObj);
+      EquilateralTriangle.validateJsonElement(jsonElement);
       validCount++;
     } catch (Exception e) {
       errorMessages.add(String.format("Deserialization for EquilateralTriangle failed with `%s`.", e.getMessage()));
@@ -316,7 +312,7 @@ public class Triangle extends AbstractOpenApiSchema {
     }
     // validate the json string with IsoscelesTriangle
     try {
-      IsoscelesTriangle.validateJsonObject(jsonObj);
+      IsoscelesTriangle.validateJsonElement(jsonElement);
       validCount++;
     } catch (Exception e) {
       errorMessages.add(String.format("Deserialization for IsoscelesTriangle failed with `%s`.", e.getMessage()));
@@ -324,14 +320,14 @@ public class Triangle extends AbstractOpenApiSchema {
     }
     // validate the json string with ScaleneTriangle
     try {
-      ScaleneTriangle.validateJsonObject(jsonObj);
+      ScaleneTriangle.validateJsonElement(jsonElement);
       validCount++;
     } catch (Exception e) {
       errorMessages.add(String.format("Deserialization for ScaleneTriangle failed with `%s`.", e.getMessage()));
       // continue to the next one
     }
     if (validCount != 1) {
-      throw new IOException(String.format("The JSON string is invalid for Triangle with oneOf schemas: EquilateralTriangle, IsoscelesTriangle, ScaleneTriangle. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonObj.toString()));
+      throw new IOException(String.format("The JSON string is invalid for Triangle with oneOf schemas: EquilateralTriangle, IsoscelesTriangle, ScaleneTriangle. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonElement.toString()));
     }
   }
 

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/TriangleInterface.java

@@ -179,24 +179,25 @@ public class TriangleInterface {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to TriangleInterface
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to TriangleInterface
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!TriangleInterface.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!TriangleInterface.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in TriangleInterface is not found in the empty JSON string", TriangleInterface.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : TriangleInterface.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if (!jsonObj.get("triangleType").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `triangleType` to be a primitive type in the JSON string but got `%s`", jsonObj.get("triangleType").toString()));
       }
@@ -239,8 +240,9 @@ public class TriangleInterface {
 
            @Override
            public TriangleInterface read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              TriangleInterface instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/User.java

@@ -498,17 +498,18 @@ public class User {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to User
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to User
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!User.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!User.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in User is not found in the empty JSON string", User.openapiRequiredFields.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("username") != null && !jsonObj.get("username").isJsonNull()) && !jsonObj.get("username").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `username` to be a primitive type in the JSON string but got `%s`", jsonObj.get("username").toString()));
       }
@@ -566,8 +567,9 @@ public class User {
 
            @Override
            public User read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              User instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Value.java

@@ -0,0 +1,295 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import org.openapitools.client.model.Scalar;
+
+
+
+import java.io.IOException;
+import java.lang.reflect.Type;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonParseException;
+import com.google.gson.TypeAdapter;
+import com.google.gson.TypeAdapterFactory;
+import com.google.gson.reflect.TypeToken;
+import com.google.gson.JsonPrimitive;
+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 com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonSerializationContext;
+import com.google.gson.JsonSerializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonParseException;
+
+import org.openapitools.client.JSON;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Value extends AbstractOpenApiSchema {
+    private static final Logger log = Logger.getLogger(Value.class.getName());
+
+    public static class CustomTypeAdapterFactory implements TypeAdapterFactory {
+        @SuppressWarnings("unchecked")
+        @Override
+        public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
+            if (!Value.class.isAssignableFrom(type.getRawType())) {
+                return null; // this class only serializes 'Value' and its subtypes
+            }
+            final TypeAdapter<JsonElement> elementAdapter = gson.getAdapter(JsonElement.class);
+            final TypeAdapter<Scalar> adapterScalar = gson.getDelegateAdapter(this, TypeToken.get(Scalar.class));
+
+            final Type typeInstance = new TypeToken<List<Scalar>>(){}.getType();
+            final TypeAdapter<List<Scalar>> adapterScalarList = (TypeAdapter<List<Scalar>>) gson.getDelegateAdapter(this, TypeToken.get(typeInstance));
+
+            return (TypeAdapter<T>) new TypeAdapter<Value>() {
+                @Override
+                public void write(JsonWriter out, Value value) throws IOException {
+                    if (value == null || value.getActualInstance() == null) {
+                        elementAdapter.write(out, null);
+                        return;
+                    }
+
+                    // check if the actual instance is of the type `Scalar`
+                    if (value.getActualInstance() instanceof Scalar) {
+                      JsonElement element = adapterScalar.toJsonTree((Scalar)value.getActualInstance());
+                      elementAdapter.write(out, element);
+                      return;
+                    }
+                    // check if the actual instance is of the type `List<Scalar>`
+                    if (value.getActualInstance() instanceof List<?>) {
+                      List<?> list = (List<?>) value.getActualInstance();
+        	            if(list.get(0) instanceof Scalar) {
+        		            JsonArray array = adapterScalarList.toJsonTree((List<Scalar>)value.getActualInstance()).getAsJsonArray();
+                        elementAdapter.write(out, array);
+                        return;
+        	            }
+                    }
+                    throw new IOException("Failed to serialize as the type doesn't match oneOf schemas: List<Scalar>, Scalar");
+                }
+
+                @Override
+                public Value read(JsonReader in) throws IOException {
+                    Object deserialized = null;
+                    JsonElement jsonElement = elementAdapter.read(in);
+
+                    int match = 0;
+                    ArrayList<String> errorMessages = new ArrayList<>();
+                    TypeAdapter actualAdapter = elementAdapter;
+
+                    // deserialize Scalar
+                    try {
+                      // validate the JSON object to see if any exception is thrown
+                      Scalar.validateJsonElement(jsonElement);
+                      actualAdapter = adapterScalar;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'Scalar'");
+                    } catch (Exception e) {
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for Scalar failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'Scalar'", e);
+                    }
+                    // deserialize List<Scalar>
+                    try {
+                      // validate the JSON object to see if any exception is thrown
+                      if (!jsonElement.isJsonArray()) {
+                        throw new IllegalArgumentException(String.format("Expected json element to be a array type in the JSON string but got `%s`", jsonElement.toString()));
+                      }
+
+                      JsonArray array = jsonElement.getAsJsonArray();
+                      // validate array items
+                      for(JsonElement element : array) {
+                        Scalar.validateJsonElement(element);
+                      }
+                      actualAdapter = adapterScalarList;
+                      match++;
+                      log.log(Level.FINER, "Input data matches schema 'List<Scalar>'");
+                    } catch (Exception e) {
+                      // deserialization failed, continue
+                      errorMessages.add(String.format("Deserialization for List<Scalar> failed with `%s`.", e.getMessage()));
+                      log.log(Level.FINER, "Input data does not match schema 'List<Scalar>'", e);
+                    }
+
+                    if (match == 1) {
+                        Value ret = new Value();
+                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonElement));
+                        return ret;
+                    }
+
+                    throw new IOException(String.format("Failed deserialization for Value: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonElement.toString()));
+                }
+            }.nullSafe();
+        }
+    }
+
+    // store a list of schema names defined in oneOf
+    public static final Map<String, Class<?>> schemas = new HashMap<String, Class<?>>();
+
+    public Value() {
+        super("oneOf", Boolean.FALSE);
+    }
+
+    public Value(List<Scalar> o) {
+        super("oneOf", Boolean.FALSE);
+        setActualInstance(o);
+    }
+
+    public Value(Scalar o) {
+        super("oneOf", Boolean.FALSE);
+        setActualInstance(o);
+    }
+
+    static {
+        schemas.put("Scalar", Scalar.class);
+        schemas.put("List<Scalar>", List.class);
+    }
+
+    @Override
+    public Map<String, Class<?>> getSchemas() {
+        return Value.schemas;
+    }
+
+    /**
+     * Set the instance that matches the oneOf child schema, check
+     * the instance parameter is valid against the oneOf child schemas:
+     * List<Scalar>, Scalar
+     *
+     * It could be an instance of the 'oneOf' schemas.
+     * The oneOf child schemas may themselves be a composed schema (allOf, anyOf, oneOf).
+     */
+    @Override
+    public void setActualInstance(Object instance) {
+        if (instance instanceof Scalar) {
+            super.setActualInstance(instance);
+            return;
+        }
+
+        if (instance instanceof List<?>) {
+            List<?> list = (List<?>) instance;
+        	if(list.get(0) instanceof Scalar) {
+        		super.setActualInstance(instance);
+        		return;
+        	}
+        }
+
+        throw new RuntimeException("Invalid instance type. Must be List<Scalar>, Scalar");
+    }
+
+    /**
+     * Get the actual instance, which can be the following:
+     * List<Scalar>, Scalar
+     *
+     * @return The actual instance (List<Scalar>, Scalar)
+     */
+    @Override
+    public Object getActualInstance() {
+        return super.getActualInstance();
+    }
+
+    /**
+     * Get the actual instance of `Scalar`. If the actual instance is not `Scalar`,
+     * the ClassCastException will be thrown.
+     *
+     * @return The actual instance of `Scalar`
+     * @throws ClassCastException if the instance is not `Scalar`
+     */
+    public Scalar getScalar() throws ClassCastException {
+        return (Scalar)super.getActualInstance();
+    }
+    /**
+     * Get the actual instance of `List<Scalar>`. If the actual instance is not `List<Scalar>`,
+     * the ClassCastException will be thrown.
+     *
+     * @return The actual instance of `List<Scalar>`
+     * @throws ClassCastException if the instance is not `List<Scalar>`
+     */
+    public List<Scalar> getScalarList() throws ClassCastException {
+        return (List<Scalar>)super.getActualInstance();
+    }
+
+ /**
+  * Validates the JSON Element and throws an exception if issues found
+  *
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Value
+  */
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+    // validate oneOf schemas one by one
+    int validCount = 0;
+    ArrayList<String> errorMessages = new ArrayList<>();
+    // validate the json string with Scalar
+    try {
+      Scalar.validateJsonElement(jsonElement);
+      validCount++;
+    } catch (Exception e) {
+      errorMessages.add(String.format("Deserialization for Scalar failed with `%s`.", e.getMessage()));
+      // continue to the next one
+    }
+    // validate the json string with List<Scalar>
+    try {
+      if (!jsonElement.isJsonArray()) {
+          throw new IllegalArgumentException(String.format("Expected json element to be a array type in the JSON string but got `%s`", jsonElement.toString()));
+      }
+      JsonArray array = jsonElement.getAsJsonArray();
+      // validate array items
+      for(JsonElement element : array) {
+        Scalar.validateJsonElement(element);
+      }
+      validCount++;
+    } catch (Exception e) {
+      errorMessages.add(String.format("Deserialization for List<Scalar> failed with `%s`.", e.getMessage()));
+      // continue to the next one
+    }
+    if (validCount != 1) {
+      throw new IOException(String.format("The JSON string is invalid for Value with oneOf schemas: List<Scalar>, Scalar. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonElement.toString()));
+    }
+  }
+
+ /**
+  * Create an instance of Value given an JSON string
+  *
+  * @param jsonString JSON string
+  * @return An instance of Value
+  * @throws IOException if the JSON string is invalid with respect to Value
+  */
+  public static Value fromJson(String jsonString) throws IOException {
+    return JSON.getGson().fromJson(jsonString, Value.class);
+  }
+
+ /**
+  * Convert an instance of Value to an JSON string
+  *
+  * @return JSON string
+  */
+  public String toJson() {
+    return JSON.getGson().toJson(this);
+  }
+}
+

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Variable.java

@@ -0,0 +1,325 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.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 org.openapitools.client.model.Value;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParseException;
+import com.google.gson.TypeAdapterFactory;
+import com.google.gson.reflect.TypeToken;
+import com.google.gson.TypeAdapter;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+import java.io.IOException;
+
+import java.lang.reflect.Type;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+
+import org.openapitools.client.JSON;
+
+/**
+ * Value object
+ */
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Variable {
+  public static final String SERIALIZED_NAME_NAME = "name";
+  @SerializedName(SERIALIZED_NAME_NAME)
+  private String name;
+
+  public static final String SERIALIZED_NAME_VALUE = "value";
+  @SerializedName(SERIALIZED_NAME_VALUE)
+  private Value value;
+
+  public Variable() {
+  }
+
+  public Variable 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 Variable value(Value value) {
+    
+    this.value = value;
+    return this;
+  }
+
+   /**
+   * Get value
+   * @return value
+  **/
+  @javax.annotation.Nonnull
+  public Value getValue() {
+    return value;
+  }
+
+
+  public void setValue(Value value) {
+    this.value = value;
+  }
+
+  /**
+   * A container for additional, undeclared properties.
+   * This is a holder for any undeclared properties as specified with
+   * the 'additionalProperties' keyword in the OAS document.
+   */
+  private Map<String, Object> additionalProperties;
+
+  /**
+   * Set the additional (undeclared) property with the specified name and value.
+   * If the property does not already exist, create it otherwise replace it.
+   *
+   * @param key name of the property
+   * @param value value of the property
+   * @return the Variable instance itself
+   */
+  public Variable putAdditionalProperty(String key, Object value) {
+    if (this.additionalProperties == null) {
+        this.additionalProperties = new HashMap<String, Object>();
+    }
+    this.additionalProperties.put(key, value);
+    return this;
+  }
+
+  /**
+   * Return the additional (undeclared) property.
+   *
+   * @return a map of objects
+   */
+  public Map<String, Object> getAdditionalProperties() {
+    return additionalProperties;
+  }
+
+  /**
+   * Return the additional (undeclared) property with the specified name.
+   *
+   * @param key name of the property
+   * @return an object
+   */
+  public Object getAdditionalProperty(String key) {
+    if (this.additionalProperties == null) {
+        return null;
+    }
+    return this.additionalProperties.get(key);
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    Variable variable = (Variable) o;
+    return Objects.equals(this.name, variable.name) &&
+        Objects.equals(this.value, variable.value)&&
+        Objects.equals(this.additionalProperties, variable.additionalProperties);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(name, value, additionalProperties);
+  }
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class Variable {\n");
+    sb.append("    name: ").append(toIndentedString(name)).append("\n");
+    sb.append("    value: ").append(toIndentedString(value)).append("\n");
+    sb.append("    additionalProperties: ").append(toIndentedString(additionalProperties)).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    ");
+  }
+
+
+  public static HashSet<String> openapiFields;
+  public static HashSet<String> openapiRequiredFields;
+
+  static {
+    // a set of all properties/fields (JSON key names)
+    openapiFields = new HashSet<String>();
+    openapiFields.add("name");
+    openapiFields.add("value");
+
+    // a set of required properties/fields (JSON key names)
+    openapiRequiredFields = new HashSet<String>();
+    openapiRequiredFields.add("name");
+    openapiRequiredFields.add("value");
+  }
+
+ /**
+  * Validates the JSON Element and throws an exception if issues found
+  *
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Variable
+  */
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Variable.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
+          throw new IllegalArgumentException(String.format("The required field(s) %s in Variable is not found in the empty JSON string", Variable.openapiRequiredFields.toString()));
+        }
+      }
+
+      // check to make sure all required properties/fields are present in the JSON string
+      for (String requiredField : Variable.openapiRequiredFields) {
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
+        }
+      }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
+      if (!jsonObj.get("name").isJsonPrimitive()) {
+        throw new IllegalArgumentException(String.format("Expected the field `name` to be a primitive type in the JSON string but got `%s`", jsonObj.get("name").toString()));
+      }
+      // validate the required field `value`
+      Value.validateJsonElement(jsonObj.get("value"));
+  }
+
+  public static class CustomTypeAdapterFactory implements TypeAdapterFactory {
+    @SuppressWarnings("unchecked")
+    @Override
+    public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
+       if (!Variable.class.isAssignableFrom(type.getRawType())) {
+         return null; // this class only serializes 'Variable' and its subtypes
+       }
+       final TypeAdapter<JsonElement> elementAdapter = gson.getAdapter(JsonElement.class);
+       final TypeAdapter<Variable> thisAdapter
+                        = gson.getDelegateAdapter(this, TypeToken.get(Variable.class));
+
+       return (TypeAdapter<T>) new TypeAdapter<Variable>() {
+           @Override
+           public void write(JsonWriter out, Variable value) throws IOException {
+             JsonObject obj = thisAdapter.toJsonTree(value).getAsJsonObject();
+             obj.remove("additionalProperties");
+             // serialize additional properties
+             if (value.getAdditionalProperties() != null) {
+               for (Map.Entry<String, Object> entry : value.getAdditionalProperties().entrySet()) {
+                 if (entry.getValue() instanceof String)
+                   obj.addProperty(entry.getKey(), (String) entry.getValue());
+                 else if (entry.getValue() instanceof Number)
+                   obj.addProperty(entry.getKey(), (Number) entry.getValue());
+                 else if (entry.getValue() instanceof Boolean)
+                   obj.addProperty(entry.getKey(), (Boolean) entry.getValue());
+                 else if (entry.getValue() instanceof Character)
+                   obj.addProperty(entry.getKey(), (Character) entry.getValue());
+                 else {
+                   obj.add(entry.getKey(), gson.toJsonTree(entry.getValue()).getAsJsonObject());
+                 }
+               }
+             }
+             elementAdapter.write(out, obj);
+           }
+
+           @Override
+           public Variable read(JsonReader in) throws IOException {
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
+             // store additional fields in the deserialized instance
+             Variable instance = thisAdapter.fromJsonTree(jsonObj);
+             for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {
+               if (!openapiFields.contains(entry.getKey())) {
+                 if (entry.getValue().isJsonPrimitive()) { // primitive type
+                   if (entry.getValue().getAsJsonPrimitive().isString())
+                     instance.putAdditionalProperty(entry.getKey(), entry.getValue().getAsString());
+                   else if (entry.getValue().getAsJsonPrimitive().isNumber())
+                     instance.putAdditionalProperty(entry.getKey(), entry.getValue().getAsNumber());
+                   else if (entry.getValue().getAsJsonPrimitive().isBoolean())
+                     instance.putAdditionalProperty(entry.getKey(), entry.getValue().getAsBoolean());
+                   else
+                     throw new IllegalArgumentException(String.format("The field `%s` has unknown primitive type. Value: %s", entry.getKey(), entry.getValue().toString()));
+                 } else if (entry.getValue().isJsonArray()) {
+                     instance.putAdditionalProperty(entry.getKey(), gson.fromJson(entry.getValue(), List.class));
+                 } else { // JSON object
+                     instance.putAdditionalProperty(entry.getKey(), gson.fromJson(entry.getValue(), HashMap.class));
+                 }
+               }
+             }
+             return instance;
+           }
+
+       }.nullSafe();
+    }
+  }
+
+ /**
+  * Create an instance of Variable given an JSON string
+  *
+  * @param jsonString JSON string
+  * @return An instance of Variable
+  * @throws IOException if the JSON string is invalid with respect to Variable
+  */
+  public static Variable fromJson(String jsonString) throws IOException {
+    return JSON.getGson().fromJson(jsonString, Variable.class);
+  }
+
+ /**
+  * Convert an instance of Variable to an JSON string
+  *
+  * @return JSON string
+  */
+  public String toJson() {
+    return JSON.getGson().toJson(this);
+  }
+}
+

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Whale.java

@@ -235,24 +235,25 @@ public class Whale {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Whale
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Whale
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!Whale.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Whale.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in Whale is not found in the empty JSON string", Whale.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : Whale.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if (!jsonObj.get("className").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `className` to be a primitive type in the JSON string but got `%s`", jsonObj.get("className").toString()));
       }
@@ -295,8 +296,9 @@ public class Whale {
 
            @Override
            public Whale read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              Whale instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Zebra.java

@@ -256,24 +256,25 @@ public class Zebra {
   }
 
  /**
-  * Validates the JSON Object and throws an exception if issues found
+  * Validates the JSON Element and throws an exception if issues found
   *
-  * @param jsonObj JSON Object
-  * @throws IOException if the JSON Object is invalid with respect to Zebra
+  * @param jsonElement JSON Element
+  * @throws IOException if the JSON Element is invalid with respect to Zebra
   */
-  public static void validateJsonObject(JsonObject jsonObj) throws IOException {
-      if (jsonObj == null) {
-        if (!Zebra.openapiRequiredFields.isEmpty()) { // has required fields but JSON object is null
+  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+      if (jsonElement == null) {
+        if (!Zebra.openapiRequiredFields.isEmpty()) { // has required fields but JSON element is null
           throw new IllegalArgumentException(String.format("The required field(s) %s in Zebra is not found in the empty JSON string", Zebra.openapiRequiredFields.toString()));
         }
       }
 
       // check to make sure all required properties/fields are present in the JSON string
       for (String requiredField : Zebra.openapiRequiredFields) {
-        if (jsonObj.get(requiredField) == null) {
-          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonObj.toString()));
+        if (jsonElement.getAsJsonObject().get(requiredField) == null) {
+          throw new IllegalArgumentException(String.format("The required field `%s` is not found in the JSON string: %s", requiredField, jsonElement.toString()));
         }
       }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
       if ((jsonObj.get("type") != null && !jsonObj.get("type").isJsonNull()) && !jsonObj.get("type").isJsonPrimitive()) {
         throw new IllegalArgumentException(String.format("Expected the field `type` to be a primitive type in the JSON string but got `%s`", jsonObj.get("type").toString()));
       }
@@ -319,8 +320,9 @@ public class Zebra {
 
            @Override
            public Zebra read(JsonReader in) throws IOException {
-             JsonObject jsonObj = elementAdapter.read(in).getAsJsonObject();
-             validateJsonObject(jsonObj);
+             JsonElement jsonElement = elementAdapter.read(in);
+             validateJsonElement(jsonElement);
+             JsonObject jsonObj = jsonElement.getAsJsonObject();
              // store additional fields in the deserialized instance
              Zebra instance = thisAdapter.fromJsonTree(jsonObj);
              for (Map.Entry<String, JsonElement> entry : jsonObj.entrySet()) {

samples/client/petstore/java/okhttp-gson/src/test/java/org/openapitools/client/JSONTest.java

@@ -4,11 +4,13 @@ import static org.junit.jupiter.api.Assertions.*;
 
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
+import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.google.gson.reflect.TypeToken;
 
 import java.io.IOException;
 import java.lang.reflect.Type;
+import java.math.BigDecimal;
 import java.nio.charset.StandardCharsets;
 import java.text.DateFormat;
 import java.text.SimpleDateFormat;
@@ -22,6 +24,7 @@ import java.util.Date;
 import java.util.GregorianCalendar;
 import java.util.Locale;
 import java.util.TimeZone;
+import java.util.List;
 
 import okio.ByteString;
 import org.junit.jupiter.api.*;
@@ -430,7 +433,7 @@ public class JSONTest {
             Exception exception = assertThrows(com.google.gson.JsonSyntaxException.class, () -> {
                 Mammal o = json.getGson().fromJson(str, Mammal.class);
             });
-            assertEquals("java.io.IOException: Failed deserialization for Mammal: 0 classes match result, expected 1. Detailed failure message for oneOf schemas: [Deserialization for Pig failed with `The JSON string is invalid for Pig with oneOf schemas: BasquePig, DanishPig. 0 class(es) match the result, expected 1. Detailed failure message for oneOf schemas: [Deserialization for BasquePig failed with `The required field `className` is not found in the JSON string: {\"cultivar\":\"golden delicious\",\"mealy\":false,\"garbage_prop\":\"abc\"}`., Deserialization for DanishPig failed with `The required field `className` is not found in the JSON string: {\"cultivar\":\"golden delicious\",\"mealy\":false,\"garbage_prop\":\"abc\"}`.]. JSON: {\"cultivar\":\"golden delicious\",\"mealy\":false,\"garbage_prop\":\"abc\"}`., Deserialization for Whale failed with `The required field `className` is not found in the JSON string: {\"cultivar\":\"golden delicious\",\"mealy\":false,\"garbage_prop\":\"abc\"}`., Deserialization for Zebra failed with `The required field `className` is not found in the JSON string: {\"cultivar\":\"golden delicious\",\"mealy\":false,\"garbage_prop\":\"abc\"}`.]. JSON: {\"cultivar\":\"golden delicious\",\"mealy\":false,\"garbage_prop\":\"abc\"}", exception.getMessage());
+            assertEquals("java.io.IOException: Failed deserialization for Mammal: 0 classes match result, expected 1. Detailed failure message for oneOf schemas: [Deserialization for Whale failed with `The required field `className` is not found in the JSON string: {\"cultivar\":\"golden delicious\",\"mealy\":false,\"garbage_prop\":\"abc\"}`., Deserialization for Zebra failed with `The required field `className` is not found in the JSON string: {\"cultivar\":\"golden delicious\",\"mealy\":false,\"garbage_prop\":\"abc\"}`., Deserialization for Pig failed with `The JSON string is invalid for Pig with oneOf schemas: BasquePig, DanishPig. 0 class(es) match the result, expected 1. Detailed failure message for oneOf schemas: [Deserialization for BasquePig failed with `The required field `className` is not found in the JSON string: {\"cultivar\":\"golden delicious\",\"mealy\":false,\"garbage_prop\":\"abc\"}`., Deserialization for DanishPig failed with `The required field `className` is not found in the JSON string: {\"cultivar\":\"golden delicious\",\"mealy\":false,\"garbage_prop\":\"abc\"}`.]. JSON: {\"cultivar\":\"golden delicious\",\"mealy\":false,\"garbage_prop\":\"abc\"}`.]. JSON: {\"cultivar\":\"golden delicious\",\"mealy\":false,\"garbage_prop\":\"abc\"}", exception.getMessage());
         }
         {
             // Try to deserialize empty object. This should fail 'oneOf' because none will match
@@ -439,7 +442,143 @@ public class JSONTest {
             Exception exception = assertThrows(com.google.gson.JsonSyntaxException.class, () -> {
                 json.getGson().fromJson(str, Mammal.class);
             });
-            assertEquals("java.io.IOException: Failed deserialization for Mammal: 0 classes match result, expected 1. Detailed failure message for oneOf schemas: [Deserialization for Pig failed with `The JSON string is invalid for Pig with oneOf schemas: BasquePig, DanishPig. 0 class(es) match the result, expected 1. Detailed failure message for oneOf schemas: [Deserialization for BasquePig failed with `The required field `className` is not found in the JSON string: {}`., Deserialization for DanishPig failed with `The required field `className` is not found in the JSON string: {}`.]. JSON: {}`., Deserialization for Whale failed with `The required field `className` is not found in the JSON string: {}`., Deserialization for Zebra failed with `The required field `className` is not found in the JSON string: {}`.]. JSON: {}", exception.getMessage());
+            assertEquals("java.io.IOException: Failed deserialization for Mammal: 0 classes match result, expected 1. Detailed failure message for oneOf schemas: [Deserialization for Whale failed with `The required field `className` is not found in the JSON string: {}`., Deserialization for Zebra failed with `The required field `className` is not found in the JSON string: {}`., Deserialization for Pig failed with `The JSON string is invalid for Pig with oneOf schemas: BasquePig, DanishPig. 0 class(es) match the result, expected 1. Detailed failure message for oneOf schemas: [Deserialization for BasquePig failed with `The required field `className` is not found in the JSON string: {}`., Deserialization for DanishPig failed with `The required field `className` is not found in the JSON string: {}`.]. JSON: {}`.]. JSON: {}", exception.getMessage());
+        }
+    }
+
+    /**
+     * Validate a oneOf schema can be deserialized into the expected class.
+     * The oneOf schema contains primitive Types.
+     */
+    @Test
+    public void testOneOfSchemaWithPrimitives() throws Exception {
+        {
+            String str = "{\"name\":\"bool_1\",\"value\":false}";
+
+            Variable variable = json.getGson().fromJson(str, Variable.class);
+            assertEquals(variable.getName(), "bool_1");
+            assertTrue(variable.getValue().getActualInstance() instanceof Scalar);
+
+            Scalar scalar = (Scalar) variable.getValue().getActualInstance();
+            assertTrue(scalar.getActualInstance() instanceof Boolean);
+
+            Boolean value = (Boolean) scalar.getActualInstance();
+            assertEquals(value, false);
+
+            assertEquals(json.getGson().toJson(variable), str);
+        }
+        {
+            String str = "{\"name\":\"string_1\",\"value\":\"string\"}";
+
+            Variable variable = json.getGson().fromJson(str, Variable.class);
+            assertEquals(variable.getName(), "string_1");
+            assertTrue(variable.getValue().getActualInstance() instanceof Scalar);
+
+            Scalar scalar = (Scalar) variable.getValue().getActualInstance();
+            assertTrue(scalar.getActualInstance() instanceof String);
+            
+            String value = (String) scalar.getActualInstance();
+            assertEquals(value, "string");
+
+            assertEquals(json.getGson().toJson(variable), str);
+        }
+        {
+            String str = "{\"name\":\"decimal_1\",\"value\":124567890.0987654321}";
+
+            Variable variable = json.getGson().fromJson(str, Variable.class);
+            assertEquals(variable.getName(), "decimal_1");
+            assertTrue(variable.getValue().getActualInstance() instanceof Scalar);
+
+            Scalar scalar = (Scalar) variable.getValue().getActualInstance();
+            assertTrue(scalar.getActualInstance() instanceof BigDecimal);
+            
+            BigDecimal value = (BigDecimal) scalar.getActualInstance();
+            assertEquals(value, new BigDecimal("124567890.0987654321"));
+
+            assertEquals(json.getGson().toJson(variable), str);
+        }
+    }
+
+    /**
+     * Validate a oneOf schema can be deserialized into the expected class.
+     * The oneOf schema contains an array with elements of primitive types.
+     */
+    @Test
+    public void testOneofSchemaWithArrayOfPrimitives() throws Exception {
+        {
+            String str = "{\"name\":\"bool_array_1\",\"value\":[false,true,false]}";
+
+            Variable variable = json.getGson().fromJson(str, Variable.class);
+            assertEquals(variable.getName(), "bool_array_1");
+            assertTrue(variable.getValue().getActualInstance() instanceof List<?>);
+
+            List<Scalar> list = (List<Scalar>) variable.getValue().getActualInstance();
+            Scalar item_0 = list.get(0);
+            Scalar item_1 = list.get(1);
+            Scalar item_2 = list.get(2);
+
+            assertTrue(item_0.getActualInstance() instanceof Boolean);
+            assertTrue(item_1.getActualInstance() instanceof Boolean);
+            assertTrue(item_2.getActualInstance() instanceof Boolean);
+
+            Boolean bool_0 = (Boolean) item_0.getActualInstance();
+            Boolean bool_1 = (Boolean) item_1.getActualInstance();
+            Boolean bool_2 = (Boolean) item_2.getActualInstance();
+            assertEquals(bool_0, false);
+            assertEquals(bool_1, true);
+            assertEquals(bool_2, false);
+
+            assertEquals(json.getGson().toJson(variable), str);
+        }
+        {
+            String str = "{\"name\":\"string_array_1\",\"value\":[\"string_0\",\"string_1\",\"string_2\"]}";
+
+            Variable variable = json.getGson().fromJson(str, Variable.class);
+            assertEquals(variable.getName(), "string_array_1");
+            assertTrue(variable.getValue().getActualInstance() instanceof List<?>);
+
+            List<Scalar> list = (List<Scalar>) variable.getValue().getActualInstance();
+            Scalar item_0 = list.get(0);
+            Scalar item_1 = list.get(1);
+            Scalar item_2 = list.get(2);
+
+            assertTrue(item_0.getActualInstance() instanceof String);
+            assertTrue(item_1.getActualInstance() instanceof String);
+            assertTrue(item_2.getActualInstance() instanceof String);
+
+            String string_0 = (String) item_0.getActualInstance();
+            String string_1 = (String) item_1.getActualInstance();
+            String string_2 = (String) item_2.getActualInstance();
+            assertEquals(string_0, "string_0");
+            assertEquals(string_1, "string_1");
+            assertEquals(string_2, "string_2");
+
+            assertEquals(json.getGson().toJson(variable), str);
+        }
+        {
+            String str = "{\"name\":\"decimal_array_1\",\"value\":[124567890.0987654321,987654321.123456789,1112222210.2222222211]}";
+
+            Variable variable = json.getGson().fromJson(str, Variable.class);
+            assertEquals(variable.getName(), "decimal_array_1");
+            assertTrue(variable.getValue().getActualInstance() instanceof List<?>);
+
+            List<Scalar> list = (List<Scalar>) variable.getValue().getActualInstance();
+            Scalar item_0 = list.get(0);
+            Scalar item_1 = list.get(1);
+            Scalar item_2 = list.get(2);
+
+            assertTrue(item_0.getActualInstance() instanceof BigDecimal);
+            assertTrue(item_1.getActualInstance() instanceof BigDecimal);
+            assertTrue(item_2.getActualInstance() instanceof BigDecimal);
+
+            BigDecimal decimal_0 = (BigDecimal) item_0.getActualInstance();
+            BigDecimal decimal_1 = (BigDecimal) item_1.getActualInstance();
+            BigDecimal decimal_2 = (BigDecimal) item_2.getActualInstance();
+            assertEquals(decimal_0, new BigDecimal("124567890.0987654321"));
+            assertEquals(decimal_1, new BigDecimal("987654321.123456789"));
+            assertEquals(decimal_2, new BigDecimal("1112222210.2222222211"));
+
+            assertEquals(json.getGson().toJson(variable), str);
         }
     }
 
@@ -547,14 +686,14 @@ public class JSONTest {
 
 
     /**
-     * Test validateJsonObject with null object
+     * Test validateJsonElement with null object
      */
     @Test
-    public void testValidateJsonObject() throws Exception {
-        JsonObject jsonObject = new JsonObject();
+    public void testValidateJsonElement() throws Exception {
+        JsonElement jsonElement = json.getGson().toJsonTree(new JsonObject());
         Exception exception = assertThrows(java.lang.IllegalArgumentException.class, () -> {
-            Pet.validateJsonObject(jsonObject);
-        });
+                Pet.validateJsonElement(jsonElement);
+                });
         assertEquals(exception.getMessage(), "The required field `photoUrls` is not found in the JSON string: {}");
     }
 

samples/client/petstore/java/okhttp-gson/src/test/java/org/openapitools/client/api/ValuesApiTest.java

@@ -0,0 +1,47 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiException;
+import org.openapitools.client.model.Variable;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * API tests for ValuesApi
+ */
+@Disabled
+public class ValuesApiTest {
+
+    private final ValuesApi api = new ValuesApi();
+
+    /**
+     * Get some primitive variable values
+     *
+     * 
+     *
+     * @throws ApiException if the Api call fails
+     */
+    @Test
+    public void getSomeValuesTest() throws ApiException {
+        Variable response = api.getSomeValues();
+        // TODO: test validations
+    }
+
+}

samples/client/petstore/java/okhttp-gson/src/test/java/org/openapitools/client/model/ScalarTest.java

@@ -0,0 +1,34 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+
+/**
+ * Model tests for Scalar
+ */
+public class ScalarTest {
+    private final Scalar model = new Scalar();
+
+    /**
+     * Model tests for Scalar
+     */
+    @Test
+    public void testScalar() {
+        // TODO: test Scalar
+    }
+
+}

samples/client/petstore/java/okhttp-gson/src/test/java/org/openapitools/client/model/ValueTest.java

@@ -0,0 +1,35 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import org.openapitools.client.model.Scalar;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+
+/**
+ * Model tests for Value
+ */
+public class ValueTest {
+    private final Value model = new Value();
+
+    /**
+     * Model tests for Value
+     */
+    @Test
+    public void testValue() {
+        // TODO: test Value
+    }
+
+}

samples/client/petstore/java/okhttp-gson/src/test/java/org/openapitools/client/model/VariableTest.java

@@ -0,0 +1,57 @@
+/*
+ * OpenAPI Petstore
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.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 org.openapitools.client.model.Value;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+
+/**
+ * Model tests for Variable
+ */
+public class VariableTest {
+    private final Variable model = new Variable();
+
+    /**
+     * Model tests for Variable
+     */
+    @Test
+    public void testVariable() {
+        // TODO: test Variable
+    }
+
+    /**
+     * Test the property 'name'
+     */
+    @Test
+    public void nameTest() {
+        // TODO: test name
+    }
+
+    /**
+     * Test the property 'value'
+     */
+    @Test
+    public void valueTest() {
+        // TODO: test value
+    }
+
+}