Fix duplicated operationId with new rule in normalizer (#19872)

* fix duplicated opeationId with new rule in normalizer * update workflow * update samples * update samples * update java samples
2025-05-12 12:40:53 +00:00 · 2024-11-11 18:12:46 +08:00 · 2024-11-11 18:12:46 +08:00 · 6bc8e0bffc
commit 6bc8e0bffc
parent e8c9722d6b
54 changed files with 5806 additions and 0 deletions
--- a/.github/workflows/samples-java-client-jdk11.yaml
+++ b/.github/workflows/samples-java-client-jdk11.yaml
@ -17,6 +17,7 @@ on:
      - samples/client/others/java/jersey2-oneOf-duplicates/**
      - samples/client/others/java/jersey2-oneOf-Mixed/**
      - samples/client/others/java/resttemplate-list-schema-validation/**
+      - samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/**
  pull_request:
    paths:
      - 'samples/client/petstore/java/**'
@ -33,6 +34,7 @@ on:
      - samples/client/others/java/jersey2-oneOf-duplicates/**
      - samples/client/others/java/jersey2-oneOf-Mixed/**
      - samples/client/others/java/resttemplate-list-schema-validation/**
+      - samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/**
 jobs:
  build:
    name: Build Java Client JDK11
@ -84,6 +86,7 @@ jobs:
          - samples/client/others/java/jersey2-oneOf-duplicates/
          - samples/client/others/java/jersey2-oneOf-Mixed/
          - samples/client/others/java/resttemplate-list-schema-validation/
+          - samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-java@v4
--- a/bin/configs/java-okhttp-gson-3.1-duplicated-operationid.yaml
+++ b/bin/configs/java-okhttp-gson-3.1-duplicated-operationid.yaml
@ -0,0 +1,12 @@
+generatorName: java
+outputDir: samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid
+library: okhttp-gson
+inputSpec: modules/openapi-generator/src/test/resources/3_1/java/duplicated_operationid.yaml
+templateDir: modules/openapi-generator/src/main/resources/Java
+validateSpec: false
+additionalProperties:
+  artifactId: petstore-okhttp-gson-31-do
+  hideGenerationTimestamp: "true"
+  disallowAdditionalPropertiesIfNotPresent: false
+openapiNormalizer:
+  FIX_DUPLICATED_OPERATIONID: true
--- a/bin/configs/java-okhttp-gson-3.1.yaml
+++ b/bin/configs/java-okhttp-gson-3.1.yaml
@ -3,6 +3,7 @@ outputDir: samples/client/petstore/java/okhttp-gson-3.1
 library: okhttp-gson
 inputSpec: modules/openapi-generator/src/test/resources/3_1/java/petstore.yaml
 templateDir: modules/openapi-generator/src/main/resources/Java
+validateSpec: false
 nameMappings:
  _type: underscoreType
  type_: typeWithUnderscore
@ -14,3 +15,5 @@ additionalProperties:
  hideGenerationTimestamp: "true"
  useOneOfDiscriminatorLookup: "true"
  disallowAdditionalPropertiesIfNotPresent: false
+openapiNormalizer:
+  FIX_DUPLICATED_OPERATIONID: true
--- a/docs/customization.md
+++ b/docs/customization.md
@ -614,3 +614,10 @@ Example:
 ```
 java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -g java -i modules/openapi-generator/src/test/resources/3_0/petstore.yaml -o /tmp/java-okhttp/ --openapi-normalizer SET_PRIMITIVE_TYPES_TO_NULLABLE="integer|number"
 ```
+
+- `FIX_DUPLICATED_OPERATIONID`: When set to true, an integer suffix will be added to duplicated operationId(s), e.g. getName => getName_0, getName_1, etc
+
+Example:
+```
+java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -g java -i modules/openapi-generator/src/test/resources/3_1/java/petstore.yaml -o /tmp/java-okhttp/ --openapi-normalizer FIX_DUPLICATED_OPERATIONID=true
+```
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/OpenAPINormalizer.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/OpenAPINormalizer.java
@ -34,6 +34,9 @@ import org.slf4j.LoggerFactory;
 import java.util.*;
 import java.util.stream.Collectors;

+import static org.openapitools.codegen.utils.StringUtils.getUniqueString;
+import static org.openapitools.codegen.utils.StringUtils.underscore;
+
 public class OpenAPINormalizer {
    private OpenAPI openAPI;
    private Map<String, String> inputRules = new HashMap<>();
@ -88,6 +91,12 @@ public class OpenAPINormalizer {
    final String SET_TAGS_TO_OPERATIONID = "SET_TAGS_TO_OPERATIONID";
    String setTagsToOperationId;

+    // when set to true, tags in all operations will be set to operationId or "default" if operationId
+    // is empty
+    final String FIX_DUPLICATED_OPERATIONID = "FIX_DUPLICATED_OPERATIONID";
+    String fixDuplicatedOperationId;
+    HashSet<String> operationIdSet = new HashSet<>();
+
    // when set to true, auto fix integer with maximum value 4294967295 (2^32-1) or long with 18446744073709551615 (2^64-1)
    // by adding x-unsigned to the schema
    final String ADD_UNSIGNED_TO_INTEGER_WITH_INVALID_MAX_VALUE = "ADD_UNSIGNED_TO_INTEGER_WITH_INVALID_MAX_VALUE";
@ -149,6 +158,7 @@ public class OpenAPINormalizer {
        ruleNames.add(KEEP_ONLY_FIRST_TAG_IN_OPERATION);
        ruleNames.add(SET_TAGS_FOR_ALL_OPERATIONS);
        ruleNames.add(SET_TAGS_TO_OPERATIONID);
+        ruleNames.add(FIX_DUPLICATED_OPERATIONID);
        ruleNames.add(ADD_UNSIGNED_TO_INTEGER_WITH_INVALID_MAX_VALUE);
        ruleNames.add(REFACTOR_ALLOF_WITH_PROPERTIES_ONLY);
        ruleNames.add(NORMALIZE_31SPEC);
@ -361,6 +371,8 @@ public class OpenAPINormalizer {
        processSetTagsForAllOperations(operation);

        processSetTagsToOperationId(operation);
+
+        processFixDuplicatedOperationId(operation);
    }

    /**
@ -939,6 +951,26 @@ public class OpenAPINormalizer {
        }
    }

+    private void processFixDuplicatedOperationId(Operation operation) {
+        if (!getRule(FIX_DUPLICATED_OPERATIONID)) {
+            return;
+        }
+
+        // skip null as default codegen will automatically generate one using path, http verb, etc
+        if (operation.getOperationId() == null) {
+            return;
+        }
+
+        String uniqueName = getUniqueString(operationIdSet, operation.getOperationId());
+
+        if (!uniqueName.equals(operation.getOperationId())) {
+            LOGGER.info("operationId {} renamed to {} to ensure uniqueness (enabled by openapi normalizer rule `FIX_DUPLICATED_OPERATIONID`)", operation.getOperationId(), uniqueName);
+            operation.setOperationId(uniqueName);
+        }
+    }
+
+
+
    /**
     * If the schema contains anyOf/oneOf and properties, remove oneOf/anyOf as these serve as rules to
     * ensure inter-dependency between properties. It's a workaround as such validation is not supported at the moment.
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/StringUtils.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/StringUtils.java
@ -283,4 +283,32 @@ public class StringUtils {
            throw new RuntimeException("Word '" + name + "' could not be escaped.");
        });
    }
+
+    /**
+     * Return a unique string based on a set of processed strings.
+     *
+     * @param processedStrings a set of strings that have been processed
+     * @param input            input to be checked for uniqueness
+     * @return a unique string
+     */
+    public static String getUniqueString(Set<String> processedStrings, String input) {
+        if (input == null) {
+            return null;
+        }
+
+        String uniqueName = input;
+        // check for input uniqueness
+        int counter = 0;
+
+        if (processedStrings.contains(uniqueName)) {
+            // look for next unique next, e.g. getName_7
+            while (processedStrings.contains(uniqueName)) {
+                uniqueName = uniqueName + "_" + counter;
+                counter++;
+            }
+        }
+
+        processedStrings.add(uniqueName);
+        return uniqueName;
+    }
 }
--- a/modules/openapi-generator/src/test/resources/3_1/java/duplicated_operationid.yaml
+++ b/modules/openapi-generator/src/test/resources/3_1/java/duplicated_operationid.yaml
@ -0,0 +1,85 @@
+openapi: 3.1.0
+servers:
+  - url: 'http://petstore.swagger.io/v2'
+info:
+  description: >-
+    This is a sample server Petstore server. For this sample, you can use the api key
+    `special-key` to test the authorization filters.
+  version: 1.0.0
+  title: OpenAPI Petstore
+  license:
+    name: Apache-2.0
+    url: 'https://www.apache.org/licenses/LICENSE-2.0.html'
+tags:
+  - name: pet
+    description: Everything about your Pets
+  - name: store
+    description: Access to Petstore orders
+  - name: user
+    description: Operations about user
+paths:
+  '/pet/{petId}':
+    get:
+      tags:
+        - pet
+      summary: Find pet by ID
+      description: Returns a single pet
+      operationId: getPetById
+      parameters:
+        - name: petId
+          in: path
+          description: ID of pet to return
+          required: true
+          schema:
+            type: integer
+            format: int64
+      responses:
+        '200':
+          description: successful operation
+          content:
+            application/xml:
+              schema:
+                $ref: '#/components/schemas/myObject'
+            application/json:
+              schema:
+                $ref: '#/components/schemas/myObject'
+        '400':
+          description: Invalid ID supplied
+        '404':
+          description: Pet not found
+      security:
+        - api_key: []
+  "/fake/duplicated/operationId":
+    get:
+      tags:
+        - fake
+      operationId: getPetById
+      responses:
+        '200':
+          description: ''
+          content:
+            application/json:
+              schema:
+                anyOf:
+                  - type: 'null'
+                  - "$ref": "#/components/schemas/myObject"
+externalDocs:
+  description: Find out more about Swagger
+  url: 'http://swagger.io'
+components:
+  securitySchemes:
+    petstore_auth:
+      type: oauth2
+      flows:
+        implicit:
+          authorizationUrl: 'http://petstore.swagger.io/api/oauth/dialog'
+          scopes:
+            'write:pets': modify pets in your account
+            'read:pets': read your pets
+    api_key:
+      type: apiKey
+      name: api_key
+      in: header
+  schemas:
+    myObject:
+      type: object
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/.github/workflows/maven.yml
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/.github/workflows/maven.yml
@ -0,0 +1,30 @@
+# This workflow will build a Java project with Maven, and cache/restore any dependencies to improve the workflow execution time
+# For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-maven
+#
+# This file is auto-generated by OpenAPI Generator (https://openapi-generator.tech)
+
+name: Java CI with Maven
+
+on:
+  push:
+    branches: [ main, master ]
+  pull_request:
+    branches: [ main, master ]
+
+jobs:
+  build:
+    name: Build OpenAPI Petstore
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        java: [ 17, 21 ]
+    steps:
+    - uses: actions/checkout@v4
+    - name: Set up JDK
+      uses: actions/setup-java@v4
+      with:
+        java-version: ${{ matrix.java }}
+        distribution: 'temurin'
+        cache: maven
+    - name: Build with Maven
+      run: mvn -B package --no-transfer-progress --file pom.xml
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/.gitignore
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/.gitignore
@ -0,0 +1,21 @@
+*.class
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.ear
+
+# exclude jar for gradle wrapper
+!gradle/wrapper/*.jar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+
+# build files
+**/target
+target
+.gradle
+build
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/.openapi-generator-ignore
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/.openapi-generator-ignore
@ -0,0 +1,23 @@
+# OpenAPI Generator Ignore
+# Generated by openapi-generator https://github.com/openapitools/openapi-generator
+
+# Use this file to prevent files from being overwritten by the generator.
+# The patterns follow closely to .gitignore or .dockerignore.
+
+# As an example, the C# client generator defines ApiClient.cs.
+# You can make changes and tell OpenAPI Generator to ignore just this file by uncommenting the following line:
+#ApiClient.cs
+
+# You can match any string of characters against a directory, file or extension with a single asterisk (*):
+#foo/*/qux
+# The above matches foo/bar/qux and foo/baz/qux, but not foo/bar/baz/qux
+
+# You can recursively match patterns against a directory, file or extension with a double asterisk (**):
+#foo/**/qux
+# This matches foo/bar/qux, foo/baz/qux, and foo/bar/baz/qux
+
+# You can also negate patterns with an exclamation (!).
+# For example, you can ignore all files in a docs folder with the file extension .md:
+#docs/*.md
+# Then explicitly reverse the ignore rule for a single file:
+#!docs/README.md
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/.openapi-generator/FILES
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/.openapi-generator/FILES
@ -0,0 +1,42 @@
+.github/workflows/maven.yml
+.gitignore
+.travis.yml
+README.md
+api/openapi.yaml
+build.gradle
+build.sbt
+docs/FakeApi.md
+docs/PetApi.md
+git_push.sh
+gradle.properties
+gradle/wrapper/gradle-wrapper.jar
+gradle/wrapper/gradle-wrapper.properties
+gradlew
+gradlew.bat
+pom.xml
+settings.gradle
+src/main/AndroidManifest.xml
+src/main/java/org/openapitools/client/ApiCallback.java
+src/main/java/org/openapitools/client/ApiClient.java
+src/main/java/org/openapitools/client/ApiException.java
+src/main/java/org/openapitools/client/ApiResponse.java
+src/main/java/org/openapitools/client/Configuration.java
+src/main/java/org/openapitools/client/GzipRequestInterceptor.java
+src/main/java/org/openapitools/client/JSON.java
+src/main/java/org/openapitools/client/Pair.java
+src/main/java/org/openapitools/client/ProgressRequestBody.java
+src/main/java/org/openapitools/client/ProgressResponseBody.java
+src/main/java/org/openapitools/client/ServerConfiguration.java
+src/main/java/org/openapitools/client/ServerVariable.java
+src/main/java/org/openapitools/client/StringUtil.java
+src/main/java/org/openapitools/client/api/FakeApi.java
+src/main/java/org/openapitools/client/api/PetApi.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
+src/main/java/org/openapitools/client/auth/HttpBearerAuth.java
+src/main/java/org/openapitools/client/auth/OAuth.java
+src/main/java/org/openapitools/client/auth/OAuthFlow.java
+src/main/java/org/openapitools/client/auth/OAuthOkHttpClient.java
+src/main/java/org/openapitools/client/auth/RetryingOAuth.java
+src/main/java/org/openapitools/client/model/AbstractOpenApiSchema.java
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/.openapi-generator/VERSION
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/.openapi-generator/VERSION
@ -0,0 +1 @@
+7.10.0-SNAPSHOT
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/.travis.yml
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/.travis.yml
@ -0,0 +1,22 @@
+#
+# Generated by OpenAPI Generator: https://openapi-generator.tech
+#
+# Ref: https://docs.travis-ci.com/user/languages/java/
+#
+language: java
+jdk:
+  - openjdk12
+  - openjdk11
+  - openjdk10
+  - openjdk9
+  - openjdk8
+before_install:
+  # ensure gradlew has proper permission
+  - chmod a+x ./gradlew
+script:
+  # test using maven
+  #- mvn test
+  # test using gradle
+  - gradle test
+  # test using sbt
+  # - sbt test
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/README.md
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/README.md
@ -0,0 +1,154 @@
+# petstore-okhttp-gson-31-do
+
+OpenAPI Petstore
+- API version: 1.0.0
+  - Generator version: 7.10.0-SNAPSHOT
+
+This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+
+
+*Automatically generated by the [OpenAPI Generator](https://openapi-generator.tech)*
+
+
+## Requirements
+
+Building the API client library requires:
+1. Java 1.8+
+2. Maven (3.8.3+)/Gradle (7.2+)
+
+## Installation
+
+To install the API client library to your local Maven repository, simply execute:
+
+```shell
+mvn clean install
+```
+
+To deploy it to a remote Maven repository instead, configure the settings of the repository and execute:
+
+```shell
+mvn clean deploy
+```
+
+Refer to the [OSSRH Guide](http://central.sonatype.org/pages/ossrh-guide.html) for more information.
+
+### Maven users
+
+Add this dependency to your project's POM:
+
+```xml
+<dependency>
+  <groupId>org.openapitools</groupId>
+  <artifactId>petstore-okhttp-gson-31-do</artifactId>
+  <version>1.0.0</version>
+  <scope>compile</scope>
+</dependency>
+```
+
+### Gradle users
+
+Add this dependency to your project's build file:
+
+```groovy
+  repositories {
+    mavenCentral()     // Needed if the 'petstore-okhttp-gson-31-do' jar has been published to maven central.
+    mavenLocal()       // Needed if the 'petstore-okhttp-gson-31-do' jar has been published to the local maven repo.
+  }
+
+  dependencies {
+     implementation "org.openapitools:petstore-okhttp-gson-31-do:1.0.0"
+  }
+```
+
+### Others
+
+At first generate the JAR by executing:
+
+```shell
+mvn clean package
+```
+
+Then manually install the following JARs:
+
+* `target/petstore-okhttp-gson-31-do-1.0.0.jar`
+* `target/lib/*.jar`
+
+## Getting Started
+
+Please follow the [installation](#installation) instruction and execute the following Java code:
+
+```java
+
+// Import classes:
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.ApiException;
+import org.openapitools.client.Configuration;
+import org.openapitools.client.model.*;
+import org.openapitools.client.api.FakeApi;
+
+public class Example {
+  public static void main(String[] args) {
+    ApiClient defaultClient = Configuration.getDefaultApiClient();
+    defaultClient.setBasePath("http://petstore.swagger.io/v2");
+
+    FakeApi apiInstance = new FakeApi(defaultClient);
+    try {
+      Object result = apiInstance.getPetById0();
+      System.out.println(result);
+    } catch (ApiException e) {
+      System.err.println("Exception when calling FakeApi#getPetById0");
+      System.err.println("Status code: " + e.getCode());
+      System.err.println("Reason: " + e.getResponseBody());
+      System.err.println("Response headers: " + e.getResponseHeaders());
+      e.printStackTrace();
+    }
+  }
+}
+
+```
+
+## Documentation for API Endpoints
+
+All URIs are relative to *http://petstore.swagger.io/v2*
+
+Class | Method | HTTP request | Description
+------------ | ------------- | ------------- | -------------
+*FakeApi* | [**getPetById0**](docs/FakeApi.md#getPetById0) | **GET** /fake/duplicated/operationId | 
+*PetApi* | [**getPetById**](docs/PetApi.md#getPetById) | **GET** /pet/{petId} | Find pet by ID
+
+
+## Documentation for Models
+
+
+
+<a id="documentation-for-authorization"></a>
+## Documentation for Authorization
+
+
+Authentication schemes defined for the API:
+<a id="petstore_auth"></a>
+### petstore_auth
+
+- **Type**: OAuth
+- **Flow**: implicit
+- **Authorization URL**: http://petstore.swagger.io/api/oauth/dialog
+- **Scopes**: 
+  - write:pets: modify pets in your account
+  - read:pets: read your pets
+
+<a id="api_key"></a>
+### api_key
+
+- **Type**: API key
+- **API key parameter name**: api_key
+- **Location**: HTTP header
+
+
+## Recommendation
+
+It's recommended to create an instance of `ApiClient` per thread in a multithreaded environment to avoid any potential issues.
+
+## Author
+
+
+
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/api/openapi.yaml
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/api/openapi.yaml
@ -0,0 +1,90 @@
+openapi: 3.1.0
+info:
+  description: "This is a sample server Petstore server. For this sample, you can\
+    \ use the api key `special-key` to test the authorization filters."
+  license:
+    name: Apache-2.0
+    url: https://www.apache.org/licenses/LICENSE-2.0.html
+  title: OpenAPI Petstore
+  version: 1.0.0
+externalDocs:
+  description: Find out more about Swagger
+  url: http://swagger.io
+servers:
+- url: http://petstore.swagger.io/v2
+tags:
+- description: Everything about your Pets
+  name: pet
+- description: Access to Petstore orders
+  name: store
+- description: Operations about user
+  name: user
+paths:
+  /pet/{petId}:
+    get:
+      description: Returns a single pet
+      operationId: getPetById
+      parameters:
+      - description: ID of pet to return
+        explode: false
+        in: path
+        name: petId
+        required: true
+        schema:
+          format: int64
+          type: integer
+        style: simple
+      responses:
+        "200":
+          content:
+            application/xml:
+              schema:
+                $ref: '#/components/schemas/myObject'
+            application/json:
+              schema:
+                $ref: '#/components/schemas/myObject'
+          description: successful operation
+        "400":
+          description: Invalid ID supplied
+        "404":
+          description: Pet not found
+      security:
+      - api_key: []
+      summary: Find pet by ID
+      tags:
+      - pet
+      x-accepts:
+      - application/json
+      - application/xml
+  /fake/duplicated/operationId:
+    get:
+      operationId: getPetById_0
+      responses:
+        "200":
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/myObject'
+          description: ""
+      tags:
+      - fake
+      x-accepts:
+      - application/json
+components:
+  schemas:
+    myObject:
+      type: object
+  securitySchemes:
+    petstore_auth:
+      flows:
+        implicit:
+          authorizationUrl: http://petstore.swagger.io/api/oauth/dialog
+          scopes:
+            write:pets: modify pets in your account
+            read:pets: read your pets
+      type: oauth2
+    api_key:
+      in: header
+      name: api_key
+      type: apiKey
+
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/build.gradle
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/build.gradle
@ -0,0 +1,168 @@
+apply plugin: 'idea'
+apply plugin: 'eclipse'
+apply plugin: 'java'
+apply plugin: 'com.diffplug.spotless'
+
+group = 'org.openapitools'
+version = '1.0.0'
+
+buildscript {
+    repositories {
+        mavenCentral()
+    }
+    dependencies {
+        classpath 'com.android.tools.build:gradle:2.3.+'
+        classpath 'com.github.dcendents:android-maven-gradle-plugin:2.1'
+        classpath 'com.diffplug.spotless:spotless-plugin-gradle:6.11.0'
+    }
+}
+
+repositories {
+    mavenCentral()
+}
+sourceSets {
+    main.java.srcDirs = ['src/main/java']
+}
+
+if(hasProperty('target') && target == 'android') {
+
+    apply plugin: 'com.android.library'
+    apply plugin: 'com.github.dcendents.android-maven'
+
+    android {
+        compileSdkVersion 25
+        buildToolsVersion '25.0.2'
+        defaultConfig {
+            minSdkVersion 14
+            targetSdkVersion 25
+        }
+        compileOptions {
+            sourceCompatibility JavaVersion.VERSION_1_8
+            targetCompatibility JavaVersion.VERSION_1_8
+        }
+
+        // Rename the aar correctly
+        libraryVariants.all { variant ->
+            variant.outputs.each { output ->
+                def outputFile = output.outputFile
+                if (outputFile != null && outputFile.name.endsWith('.aar')) {
+                    def fileName = "${project.name}-${variant.baseName}-${version}.aar"
+                    output.outputFile = new File(outputFile.parent, fileName)
+                }
+            }
+        }
+
+        dependencies {
+            provided "jakarta.annotation:jakarta.annotation-api:$jakarta_annotation_version"
+        }
+    }
+
+    afterEvaluate {
+        android.libraryVariants.all { variant ->
+            def task = project.tasks.create "jar${variant.name.capitalize()}", Jar
+            task.description = "Create jar artifact for ${variant.name}"
+            task.dependsOn variant.javaCompile
+            task.from variant.javaCompile.destinationDirectory
+            task.destinationDirectory = project.file("${project.buildDir}/outputs/jar")
+            task.archiveFileName = "${project.name}-${variant.baseName}-${version}.jar"
+            artifacts.add('archives', task)
+        }
+    }
+
+    task sourcesJar(type: Jar) {
+        from android.sourceSets.main.java.srcDirs
+        classifier = 'sources'
+    }
+
+    artifacts {
+        archives sourcesJar
+    }
+
+} else {
+
+    apply plugin: 'java'
+    apply plugin: 'maven-publish'
+
+    sourceCompatibility = JavaVersion.VERSION_1_8
+    targetCompatibility = JavaVersion.VERSION_1_8
+
+    publishing {
+        publications {
+            maven(MavenPublication) {
+               artifactId = 'petstore-okhttp-gson-31-do'
+               from components.java
+            }
+        }
+    }
+
+    task execute(type:JavaExec) {
+       main = System.getProperty('mainClass')
+       classpath = sourceSets.main.runtimeClasspath
+    }
+}
+
+ext {
+    jakarta_annotation_version = "1.3.5"
+}
+
+dependencies {
+    implementation 'io.swagger:swagger-annotations:1.6.8'
+    implementation "com.google.code.findbugs:jsr305:3.0.2"
+    implementation 'com.squareup.okhttp3:okhttp:4.12.0'
+    implementation 'com.squareup.okhttp3:logging-interceptor:4.12.0'
+    implementation 'com.google.code.gson:gson:2.9.1'
+    implementation 'io.gsonfire:gson-fire:1.9.0'
+    implementation 'jakarta.ws.rs:jakarta.ws.rs-api:2.1.6'
+    implementation 'org.openapitools:jackson-databind-nullable:0.2.6'
+    implementation group: 'org.apache.oltu.oauth2', name: 'org.apache.oltu.oauth2.client', version: '1.0.2'
+    implementation group: 'org.apache.commons', name: 'commons-lang3', version: '3.12.0'
+    implementation "jakarta.annotation:jakarta.annotation-api:$jakarta_annotation_version"
+    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.10.3'
+    testImplementation 'org.mockito:mockito-core:3.12.4'
+    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.10.3'
+}
+
+javadoc {
+    options.tags = [ "http.response.details:a:Http Response Details" ]
+}
+
+// Use spotless plugin to automatically format code, remove unused import, etc
+// To apply changes directly to the file, run `gradlew spotlessApply`
+// Ref: https://github.com/diffplug/spotless/tree/main/plugin-gradle
+spotless {
+    // comment out below to run spotless as part of the `check` task
+    enforceCheck false
+
+    format 'misc', {
+        // define the files (e.g. '*.gradle', '*.md') to apply `misc` to
+        target '.gitignore'
+
+        // define the steps to apply to those files
+        trimTrailingWhitespace()
+        indentWithSpaces() // Takes an integer argument if you don't like 4
+        endWithNewline()
+    }
+    java {
+        // don't need to set target, it is inferred from java
+
+        // apply a specific flavor of google-java-format
+        googleJavaFormat('1.8').aosp().reflowLongStrings()
+
+        removeUnusedImports()
+        importOrder()
+    }
+}
+
+test {
+    // Enable JUnit 5 (Gradle 4.6+).
+    useJUnitPlatform()
+
+    // Always run tests, even when nothing changed.
+    dependsOn 'cleanTest'
+
+    // Show test results.
+    testLogging {
+        events "passed", "skipped", "failed"
+    }
+
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/build.sbt
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/build.sbt
@ -0,0 +1,28 @@
+lazy val root = (project in file(".")).
+  settings(
+    organization := "org.openapitools",
+    name := "petstore-okhttp-gson-31-do",
+    version := "1.0.0",
+    scalaVersion := "2.11.4",
+    scalacOptions ++= Seq("-feature"),
+    javacOptions in compile ++= Seq("-Xlint:deprecation"),
+    publishArtifact in (Compile, packageDoc) := false,
+    resolvers += Resolver.mavenLocal,
+    libraryDependencies ++= Seq(
+      "io.swagger" % "swagger-annotations" % "1.6.5",
+      "com.squareup.okhttp3" % "okhttp" % "4.12.0",
+      "com.squareup.okhttp3" % "logging-interceptor" % "4.12.0",
+      "com.google.code.gson" % "gson" % "2.9.1",
+      "org.apache.commons" % "commons-lang3" % "3.12.0",
+      "jakarta.ws.rs" % "jakarta.ws.rs-api" % "2.1.6",
+      "org.openapitools" % "jackson-databind-nullable" % "0.2.6",
+      "org.apache.oltu.oauth2" % "org.apache.oltu.oauth2.client" % "1.0.2",
+      "io.gsonfire" % "gson-fire" % "1.9.0" % "compile",
+      "jakarta.annotation" % "jakarta.annotation-api" % "1.3.5" % "compile",
+      "com.google.code.findbugs" % "jsr305" % "3.0.2" % "compile",
+      "jakarta.annotation" % "jakarta.annotation-api" % "1.3.5" % "compile",
+      "org.junit.jupiter" % "junit-jupiter-api" % "5.10.3" % "test",
+      "com.novocode" % "junit-interface" % "0.10" % "test",
+      "org.mockito" % "mockito-core" % "3.12.4" % "test"
+    )
+  )
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/docs/FakeApi.md
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/docs/FakeApi.md
@ -0,0 +1,65 @@
+# FakeApi
+
+All URIs are relative to *http://petstore.swagger.io/v2*
+
+| Method | HTTP request | Description |
+|------------- | ------------- | -------------|
+| [**getPetById0**](FakeApi.md#getPetById0) | **GET** /fake/duplicated/operationId |  |
+
+
+<a id="getPetById0"></a>
+# **getPetById0**
+> Object getPetById0()
+
+
+
+### 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.FakeApi;
+
+public class Example {
+  public static void main(String[] args) {
+    ApiClient defaultClient = Configuration.getDefaultApiClient();
+    defaultClient.setBasePath("http://petstore.swagger.io/v2");
+
+    FakeApi apiInstance = new FakeApi(defaultClient);
+    try {
+      Object result = apiInstance.getPetById0();
+      System.out.println(result);
+    } catch (ApiException e) {
+      System.err.println("Exception when calling FakeApi#getPetById0");
+      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
+
+**Object**
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+ - **Content-Type**: Not defined
+ - **Accept**: application/json
+
+### HTTP response details
+| Status code | Description | Response headers |
+|-------------|-------------|------------------|
+| **200** |  |  -  |
+
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/docs/PetApi.md
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/docs/PetApi.md
@ -0,0 +1,80 @@
+# PetApi
+
+All URIs are relative to *http://petstore.swagger.io/v2*
+
+| Method | HTTP request | Description |
+|------------- | ------------- | -------------|
+| [**getPetById**](PetApi.md#getPetById) | **GET** /pet/{petId} | Find pet by ID |
+
+
+<a id="getPetById"></a>
+# **getPetById**
+> Object getPetById(petId)
+
+Find pet by ID
+
+Returns a single pet
+
+### Example
+```java
+// Import classes:
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.ApiException;
+import org.openapitools.client.Configuration;
+import org.openapitools.client.auth.*;
+import org.openapitools.client.models.*;
+import org.openapitools.client.api.PetApi;
+
+public class Example {
+  public static void main(String[] args) {
+    ApiClient defaultClient = Configuration.getDefaultApiClient();
+    defaultClient.setBasePath("http://petstore.swagger.io/v2");
+    
+    // Configure API key authorization: api_key
+    ApiKeyAuth api_key = (ApiKeyAuth) defaultClient.getAuthentication("api_key");
+    api_key.setApiKey("YOUR API KEY");
+    // Uncomment the following line to set a prefix for the API key, e.g. "Token" (defaults to null)
+    //api_key.setApiKeyPrefix("Token");
+
+    PetApi apiInstance = new PetApi(defaultClient);
+    Long petId = 56L; // Long | ID of pet to return
+    try {
+      Object result = apiInstance.getPetById(petId);
+      System.out.println(result);
+    } catch (ApiException e) {
+      System.err.println("Exception when calling PetApi#getPetById");
+      System.err.println("Status code: " + e.getCode());
+      System.err.println("Reason: " + e.getResponseBody());
+      System.err.println("Response headers: " + e.getResponseHeaders());
+      e.printStackTrace();
+    }
+  }
+}
+```
+
+### Parameters
+
+| Name | Type | Description  | Notes |
+|------------- | ------------- | ------------- | -------------|
+| **petId** | **Long**| ID of pet to return | |
+
+### Return type
+
+**Object**
+
+### Authorization
+
+[api_key](../README.md#api_key)
+
+### HTTP request headers
+
+ - **Content-Type**: Not defined
+ - **Accept**: application/xml, application/json
+
+### HTTP response details
+| Status code | Description | Response headers |
+|-------------|-------------|------------------|
+| **200** | successful operation |  -  |
+| **400** | Invalid ID supplied |  -  |
+| **404** | Pet not found |  -  |
+
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/git_push.sh
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/git_push.sh
@ -0,0 +1,57 @@
+#!/bin/sh
+# ref: https://help.github.com/articles/adding-an-existing-project-to-github-using-the-command-line/
+#
+# Usage example: /bin/sh ./git_push.sh wing328 openapi-petstore-perl "minor update" "gitlab.com"
+
+git_user_id=$1
+git_repo_id=$2
+release_note=$3
+git_host=$4
+
+if [ "$git_host" = "" ]; then
+    git_host="github.com"
+    echo "[INFO] No command line input provided. Set \$git_host to $git_host"
+fi
+
+if [ "$git_user_id" = "" ]; then
+    git_user_id="GIT_USER_ID"
+    echo "[INFO] No command line input provided. Set \$git_user_id to $git_user_id"
+fi
+
+if [ "$git_repo_id" = "" ]; then
+    git_repo_id="GIT_REPO_ID"
+    echo "[INFO] No command line input provided. Set \$git_repo_id to $git_repo_id"
+fi
+
+if [ "$release_note" = "" ]; then
+    release_note="Minor update"
+    echo "[INFO] No command line input provided. Set \$release_note to $release_note"
+fi
+
+# Initialize the local directory as a Git repository
+git init
+
+# Adds the files in the local repository and stages them for commit.
+git add .
+
+# Commits the tracked changes and prepares them to be pushed to a remote repository.
+git commit -m "$release_note"
+
+# Sets the new remote
+git_remote=$(git remote)
+if [ "$git_remote" = "" ]; then # git remote not defined
+
+    if [ "$GIT_TOKEN" = "" ]; then
+        echo "[INFO] \$GIT_TOKEN (environment variable) is not set. Using the git credential in your environment."
+        git remote add origin https://${git_host}/${git_user_id}/${git_repo_id}.git
+    else
+        git remote add origin https://${git_user_id}:"${GIT_TOKEN}"@${git_host}/${git_user_id}/${git_repo_id}.git
+    fi
+
+fi
+
+git pull origin master
+
+# Pushes (Forces) the changes in the local repository up to the remote repository
+echo "Git pushing to https://${git_host}/${git_user_id}/${git_repo_id}.git"
+git push origin master 2>&1 | grep -v 'To https'
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/gradle.properties
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/gradle.properties
@ -0,0 +1,6 @@
+# This file is automatically generated by OpenAPI Generator (https://github.com/openAPITools/openapi-generator).
+# To include other gradle properties as part of the code generation process, please use the `gradleProperties` option.
+#
+# Gradle properties reference: https://docs.gradle.org/current/userguide/build_environment.html#sec:gradle_configuration_properties
+# For example, uncomment below to build for Android
+#target = android
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/gradle/wrapper/gradle-wrapper.jar
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/gradle/wrapper/gradle-wrapper.jar
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/gradle/wrapper/gradle-wrapper.properties
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/gradle/wrapper/gradle-wrapper.properties
@ -0,0 +1,7 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.7-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/gradlew
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/gradlew
@ -0,0 +1,249 @@
+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/HEAD/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+[ -h "$app_path" ]
+do
+ls=$( ls -ld "$app_path" )
+link=${ls#*' -> '}
+case $link in             #(
+/*)   app_path=$link ;; #(
+*)    app_path=$APP_HOME$link ;;
+esac
+done
+
+# This is normally unused
+# shellcheck disable=SC2034
+APP_BASE_NAME=${0##*/}
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd "${APP_HOME:-./}" > /dev/null && pwd -P ) || exit
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+echo "$*"
+} >&2
+
+die () {
+echo
+echo "$*"
+echo
+exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+CYGWIN* )         cygwin=true  ;; #(
+Darwin* )         darwin=true  ;; #(
+MSYS* | MINGW* )  msys=true    ;; #(
+NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+# IBM's JDK on AIX uses strange locations for the executables
+JAVACMD=$JAVA_HOME/jre/sh/java
+else
+JAVACMD=$JAVA_HOME/bin/java
+fi
+if [ ! -x "$JAVACMD" ] ; then
+die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+else
+JAVACMD=java
+if ! command -v java >/dev/null 2>&1
+then
+die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+case $MAX_FD in #(
+max*)
+# In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+# shellcheck disable=SC2039,SC3045
+MAX_FD=$( ulimit -H -n ) ||
+warn "Could not query maximum file descriptor limit"
+esac
+case $MAX_FD in  #(
+'' | soft) :;; #(
+*)
+# In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+# shellcheck disable=SC2039,SC3045
+ulimit -n "$MAX_FD" ||
+warn "Could not set maximum file descriptor limit to $MAX_FD"
+esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+# Now convert the arguments - kludge to limit ourselves to /bin/sh
+for arg do
+if
+case $arg in                                #(
+-*)   false ;;                            # don't mess with options #(
+/?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+[ -e "$t" ] ;;                      #(
+*)    false ;;
+esac
+then
+arg=$( cygpath --path --ignore --mixed "$arg" )
+fi
+# Roll the args list around exactly as many times as the number of
+# args, so each arg winds up back in the position where it started, but
+# possibly modified.
+#
+# NB: a `for` loop captures its iteration list before it begins, so
+# changing the positional parameters here affects neither the number of
+# iterations, nor the values presented in `arg`.
+shift                   # remove old arg
+set -- "$@" "$arg"      # push replacement arg
+done
+fi
+
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
+
+set -- \
+"-Dorg.gradle.appname=$APP_BASE_NAME" \
+-classpath "$CLASSPATH" \
+org.gradle.wrapper.GradleWrapperMain \
+"$@"
+
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+die "xargs is not available"
+fi
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+xargs -n1 |
+sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+tr '\n' ' '
+)" '"$@"'
+
+exec "$JAVACMD" "$@"
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/gradlew.bat
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/gradlew.bat
@ -0,0 +1,92 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%"=="" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%"=="" set DIRNAME=.
+@rem This is normally unused
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if %ERRORLEVEL% equ 0 goto execute
+
+echo. 1>&2
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo. 1>&2
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if %ERRORLEVEL% equ 0 goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+set EXIT_CODE=%ERRORLEVEL%
+if %EXIT_CODE% equ 0 set EXIT_CODE=1
+if not ""=="%GRADLE_EXIT_CONSOLE%" exit %EXIT_CODE%
+exit /b %EXIT_CODE%
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/pom.xml
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/pom.xml
@ -0,0 +1,345 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>org.openapitools</groupId>
+    <artifactId>petstore-okhttp-gson-31-do</artifactId>
+    <packaging>jar</packaging>
+    <name>petstore-okhttp-gson-31-do</name>
+    <version>1.0.0</version>
+    <url>https://github.com/openapitools/openapi-generator</url>
+    <description>OpenAPI Java</description>
+    <scm>
+        <connection>scm:git:git@github.com:openapitools/openapi-generator.git</connection>
+        <developerConnection>scm:git:git@github.com:openapitools/openapi-generator.git</developerConnection>
+        <url>https://github.com/openapitools/openapi-generator</url>
+    </scm>
+
+    <licenses>
+        <license>
+            <name>Unlicense</name>
+            <url>https://www.apache.org/licenses/LICENSE-2.0.html</url>
+            <distribution>repo</distribution>
+        </license>
+    </licenses>
+
+    <developers>
+        <developer>
+            <name>OpenAPI-Generator Contributors</name>
+            <email>team@openapitools.org</email>
+            <organization>OpenAPITools.org</organization>
+            <organizationUrl>http://openapitools.org</organizationUrl>
+        </developer>
+    </developers>
+
+    <build>
+        <plugins>
+           <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.8.1</version>
+                <configuration>
+                    <fork>true</fork>
+                    <meminitial>128m</meminitial>
+                    <maxmem>512m</maxmem>
+                    <compilerArgs>
+                        <arg>-Xlint:all</arg>
+                        <arg>-J-Xss4m</arg><!-- Compiling the generated JSON.java file may require larger stack size. -->
+                    </compilerArgs>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-enforcer-plugin</artifactId>
+                <version>3.4.1</version>
+                <executions>
+                    <execution>
+                        <id>enforce-maven</id>
+                        <goals>
+                            <goal>enforce</goal>
+                        </goals>
+                        <configuration>
+                            <rules>
+                                <requireMavenVersion>
+                                    <version>2.2.0</version>
+                                </requireMavenVersion>
+                            </rules>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>2.22.2</version>
+                <configuration>
+                    <systemPropertyVariables>
+                        <property>
+                            <name>loggerPath</name>
+                            <value>conf/log4j.properties</value>
+                        </property>
+                    </systemPropertyVariables>
+                    <argLine>-Xms512m -Xmx1500m</argLine>
+                    <parallel>methods</parallel>
+                    <threadCount>10</threadCount>
+                </configuration>
+                <dependencies>
+                    <!--Custom provider and engine for Junit 5 to surefire-->
+                    <dependency>
+                        <groupId>org.junit.jupiter</groupId>
+                        <artifactId>junit-jupiter-engine</artifactId>
+                        <version>${junit-version}</version>
+                    </dependency>
+                </dependencies>
+            </plugin>
+            <plugin>
+                <artifactId>maven-dependency-plugin</artifactId>
+                <version>3.6.1</version>
+                <executions>
+                    <execution>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>copy-dependencies</goal>
+                        </goals>
+                        <configuration>
+                            <outputDirectory>${project.build.directory}/lib</outputDirectory>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+            <!-- attach test jar -->
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-jar-plugin</artifactId>
+                <version>3.3.0</version>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>test-jar</goal>
+                        </goals>
+                    </execution>
+                </executions>
+                <configuration>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>build-helper-maven-plugin</artifactId>
+                <version>3.5.0</version>
+                <executions>
+                    <execution>
+                        <id>add_sources</id>
+                        <phase>generate-sources</phase>
+                        <goals>
+                            <goal>add-source</goal>
+                        </goals>
+                        <configuration>
+                            <sources>
+                                <source>src/main/java</source>
+                            </sources>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>add_test_sources</id>
+                        <phase>generate-test-sources</phase>
+                        <goals>
+                            <goal>add-test-source</goal>
+                        </goals>
+                        <configuration>
+                            <sources>
+                                <source>src/test/java</source>
+                            </sources>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-javadoc-plugin</artifactId>
+                <version>3.6.3</version>
+                <executions>
+                    <execution>
+                        <id>attach-javadocs</id>
+                        <goals>
+                            <goal>jar</goal>
+                        </goals>
+                    </execution>
+                </executions>
+                <configuration>
+                    <doclint>none</doclint>
+                    <tags>
+                        <tag>
+                            <name>http.response.details</name>
+                            <placement>a</placement>
+                            <head>Http Response Details:</head>
+                        </tag>
+                    </tags>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-source-plugin</artifactId>
+                <version>3.3.0</version>
+                <executions>
+                    <execution>
+                        <id>attach-sources</id>
+                        <goals>
+                            <goal>jar-no-fork</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+            <!-- Use spotless plugin to automatically format code, remove unused import, etc
+                 To apply changes directly to the file, run `mvn spotless:apply`
+                 Ref: https://github.com/diffplug/spotless/tree/main/plugin-maven
+            -->
+            <plugin>
+              <groupId>com.diffplug.spotless</groupId>
+              <artifactId>spotless-maven-plugin</artifactId>
+              <version>${spotless.version}</version>
+              <configuration>
+                <formats>
+                  <!-- you can define as many formats as you want, each is independent -->
+                  <format>
+                    <!-- define the files to apply to -->
+                    <includes>
+                      <include>.gitignore</include>
+                    </includes>
+                    <!-- define the steps to apply to those files -->
+                    <trimTrailingWhitespace/>
+                    <endWithNewline/>
+                    <indent>
+                      <spaces>true</spaces> <!-- or <tabs>true</tabs> -->
+                      <spacesPerTab>4</spacesPerTab> <!-- optional, default is 4 -->
+                    </indent>
+                  </format>
+                </formats>
+                <!-- define a language-specific format -->
+                <java>
+                  <!-- no need to specify files, inferred automatically, but you can if you want -->
+
+                  <!-- apply a specific flavor of google-java-format and reflow long strings -->
+                  <googleJavaFormat>
+                    <version>1.8</version>
+                    <style>AOSP</style>
+                    <reflowLongStrings>true</reflowLongStrings>
+                  </googleJavaFormat>
+
+                  <removeUnusedImports/>
+                  <importOrder/>
+
+                </java>
+              </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <profiles>
+        <profile>
+            <id>sign-artifacts</id>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-gpg-plugin</artifactId>
+                        <version>3.2.1</version>
+                        <executions>
+                            <execution>
+                                <id>sign-artifacts</id>
+                                <phase>verify</phase>
+                                <goals>
+                                    <goal>sign</goal>
+                                </goals>
+                            </execution>
+                        </executions>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
+    </profiles>
+
+    <dependencies>
+        <!-- @Nullable annotation -->
+        <dependency>
+            <groupId>com.google.code.findbugs</groupId>
+            <artifactId>jsr305</artifactId>
+            <version>3.0.2</version>
+        </dependency>
+        <dependency>
+            <groupId>com.squareup.okhttp3</groupId>
+            <artifactId>okhttp</artifactId>
+            <version>${okhttp-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.squareup.okhttp3</groupId>
+            <artifactId>logging-interceptor</artifactId>
+            <version>${okhttp-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.google.code.gson</groupId>
+            <artifactId>gson</artifactId>
+            <version>${gson-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>io.gsonfire</groupId>
+            <artifactId>gson-fire</artifactId>
+            <version>${gson-fire-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.oltu.oauth2</groupId>
+            <artifactId>org.apache.oltu.oauth2.client</artifactId>
+            <version>1.0.2</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>jakarta.annotation</groupId>
+            <artifactId>jakarta.annotation-api</artifactId>
+            <version>${jakarta-annotation-version}</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.openapitools</groupId>
+            <artifactId>jackson-databind-nullable</artifactId>
+            <version>${jackson-databind-nullable-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>jakarta.ws.rs</groupId>
+            <artifactId>jakarta.ws.rs-api</artifactId>
+            <version>${jakarta.ws.rs-api-version}</version>
+        </dependency>
+        <!-- test dependencies -->
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-engine</artifactId>
+            <version>${junit-version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.platform</groupId>
+            <artifactId>junit-platform-runner</artifactId>
+            <version>${junit-platform-runner.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+    <properties>
+        <java.version>1.8</java.version>
+        <maven.compiler.source>${java.version}</maven.compiler.source>
+        <maven.compiler.target>${java.version}</maven.compiler.target>
+        <gson-fire-version>1.9.0</gson-fire-version>
+        <okhttp-version>4.12.0</okhttp-version>
+        <gson-version>2.10.1</gson-version>
+        <commons-lang3-version>3.14.0</commons-lang3-version>
+        <jackson-databind-nullable-version>0.2.6</jackson-databind-nullable-version>
+        <jakarta-annotation-version>1.3.5</jakarta-annotation-version>
+        <beanvalidation-version>2.0.2</beanvalidation-version>
+        <junit-version>5.10.3</junit-version>
+        <junit-platform-runner.version>1.10.0</junit-platform-runner.version>
+        <jakarta.ws.rs-api-version>2.1.6</jakarta.ws.rs-api-version>
+        <jsr311-api-version>1.1.1</jsr311-api-version>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <spotless.version>2.43.0</spotless.version>
+    </properties>
+</project>
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/settings.gradle
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/settings.gradle
@ -0,0 +1 @@
+rootProject.name = "petstore-okhttp-gson-31-do"
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/AndroidManifest.xml
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/AndroidManifest.xml
@ -0,0 +1,3 @@
+<manifest package="org.openapitools.client" xmlns:android="http://schemas.android.com/apk/res/android">
+    <application />
+</manifest>
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/ApiCallback.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/ApiCallback.java
@ -0,0 +1,62 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client;
+
+import java.io.IOException;
+
+import java.util.Map;
+import java.util.List;
+
+/**
+ * Callback for asynchronous API call.
+ *
+ * @param <T> The return type
+ */
+public interface ApiCallback<T> {
+    /**
+     * This is called when the API call fails.
+     *
+     * @param e The exception causing the failure
+     * @param statusCode Status code of the response if available, otherwise it would be 0
+     * @param responseHeaders Headers of the response if available, otherwise it would be null
+     */
+    void onFailure(ApiException e, int statusCode, Map<String, List<String>> responseHeaders);
+
+    /**
+     * This is called when the API call succeeded.
+     *
+     * @param result The result deserialized from response
+     * @param statusCode Status code of the response
+     * @param responseHeaders Headers of the response
+     */
+    void onSuccess(T result, int statusCode, Map<String, List<String>> responseHeaders);
+
+    /**
+     * This is called when the API upload processing.
+     *
+     * @param bytesWritten bytes Written
+     * @param contentLength content length of request body
+     * @param done write end
+     */
+    void onUploadProgress(long bytesWritten, long contentLength, boolean done);
+
+    /**
+     * This is called when the API download processing.
+     *
+     * @param bytesRead bytes Read
+     * @param contentLength content length of the response
+     * @param done Read end
+     */
+    void onDownloadProgress(long bytesRead, long contentLength, boolean done);
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/ApiClient.java
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/ApiException.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/ApiException.java
@ -0,0 +1,167 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client;
+
+import java.util.Map;
+import java.util.List;
+
+
+/**
+ * <p>ApiException class.</p>
+ */
+@SuppressWarnings("serial")
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", comments = "Generator version: 7.10.0-SNAPSHOT")
+public class ApiException extends Exception {
+    private static final long serialVersionUID = 1L;
+
+    private int code = 0;
+    private Map<String, List<String>> responseHeaders = null;
+    private String responseBody = null;
+
+    /**
+     * <p>Constructor for ApiException.</p>
+     */
+    public ApiException() {}
+
+    /**
+     * <p>Constructor for ApiException.</p>
+     *
+     * @param throwable a {@link java.lang.Throwable} object
+     */
+    public ApiException(Throwable throwable) {
+        super(throwable);
+    }
+
+    /**
+     * <p>Constructor for ApiException.</p>
+     *
+     * @param message the error message
+     */
+    public ApiException(String message) {
+        super(message);
+    }
+
+    /**
+     * <p>Constructor for ApiException.</p>
+     *
+     * @param message the error message
+     * @param throwable a {@link java.lang.Throwable} object
+     * @param code HTTP status code
+     * @param responseHeaders a {@link java.util.Map} of HTTP response headers
+     * @param responseBody the response body
+     */
+    public ApiException(String message, Throwable throwable, int code, Map<String, List<String>> responseHeaders, String responseBody) {
+        super(message, throwable);
+        this.code = code;
+        this.responseHeaders = responseHeaders;
+        this.responseBody = responseBody;
+    }
+
+    /**
+     * <p>Constructor for ApiException.</p>
+     *
+     * @param message the error message
+     * @param code HTTP status code
+     * @param responseHeaders a {@link java.util.Map} of HTTP response headers
+     * @param responseBody the response body
+     */
+    public ApiException(String message, int code, Map<String, List<String>> responseHeaders, String responseBody) {
+        this(message, (Throwable) null, code, responseHeaders, responseBody);
+    }
+
+    /**
+     * <p>Constructor for ApiException.</p>
+     *
+     * @param message the error message
+     * @param throwable a {@link java.lang.Throwable} object
+     * @param code HTTP status code
+     * @param responseHeaders a {@link java.util.Map} of HTTP response headers
+     */
+    public ApiException(String message, Throwable throwable, int code, Map<String, List<String>> responseHeaders) {
+        this(message, throwable, code, responseHeaders, null);
+    }
+
+    /**
+     * <p>Constructor for ApiException.</p>
+     *
+     * @param code HTTP status code
+     * @param responseHeaders a {@link java.util.Map} of HTTP response headers
+     * @param responseBody the response body
+     */
+    public ApiException(int code, Map<String, List<String>> responseHeaders, String responseBody) {
+        this("Response Code: " + code + " Response Body: " + responseBody, (Throwable) null, code, responseHeaders, responseBody);
+    }
+
+    /**
+     * <p>Constructor for ApiException.</p>
+     *
+     * @param code HTTP status code
+     * @param message a {@link java.lang.String} object
+     */
+    public ApiException(int code, String message) {
+        super(message);
+        this.code = code;
+    }
+
+    /**
+     * <p>Constructor for ApiException.</p>
+     *
+     * @param code HTTP status code
+     * @param message the error message
+     * @param responseHeaders a {@link java.util.Map} of HTTP response headers
+     * @param responseBody the response body
+     */
+    public ApiException(int code, String message, Map<String, List<String>> responseHeaders, String responseBody) {
+        this(code, message);
+        this.responseHeaders = responseHeaders;
+        this.responseBody = responseBody;
+    }
+
+    /**
+     * Get the HTTP status code.
+     *
+     * @return HTTP status code
+     */
+    public int getCode() {
+        return code;
+    }
+
+    /**
+     * Get the HTTP response headers.
+     *
+     * @return A map of list of string
+     */
+    public Map<String, List<String>> getResponseHeaders() {
+        return responseHeaders;
+    }
+
+    /**
+     * Get the HTTP response body.
+     *
+     * @return Response body in the form of string
+     */
+    public String getResponseBody() {
+        return responseBody;
+    }
+
+    /**
+     * Get the exception message including HTTP response data.
+     *
+     * @return The exception message
+     */
+    public String getMessage() {
+        return String.format("Message: %s%nHTTP response code: %s%nHTTP response body: %s%nHTTP response headers: %s",
+                super.getMessage(), this.getCode(), this.getResponseBody(), this.getResponseHeaders());
+    }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/ApiResponse.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/ApiResponse.java
@ -0,0 +1,76 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client;
+
+import java.util.List;
+import java.util.Map;
+
+/**
+ * API response returned by API call.
+ */
+public class ApiResponse<T> {
+    final private int statusCode;
+    final private Map<String, List<String>> headers;
+    final private T data;
+
+    /**
+     * <p>Constructor for ApiResponse.</p>
+     *
+     * @param statusCode The status code of HTTP response
+     * @param headers The headers of HTTP response
+     */
+    public ApiResponse(int statusCode, Map<String, List<String>> headers) {
+        this(statusCode, headers, null);
+    }
+
+    /**
+     * <p>Constructor for ApiResponse.</p>
+     *
+     * @param statusCode The status code of HTTP response
+     * @param headers The headers of HTTP response
+     * @param data The object deserialized from response bod
+     */
+    public ApiResponse(int statusCode, Map<String, List<String>> headers, T data) {
+        this.statusCode = statusCode;
+        this.headers = headers;
+        this.data = data;
+    }
+
+    /**
+     * <p>Get the <code>status code</code>.</p>
+     *
+     * @return the status code
+     */
+    public int getStatusCode() {
+        return statusCode;
+    }
+
+    /**
+     * <p>Get the <code>headers</code>.</p>
+     *
+     * @return a {@link java.util.Map} of headers 
+     */
+    public Map<String, List<String>> getHeaders() {
+        return headers;
+    }
+
+    /**
+     * <p>Get the <code>data</code>.</p>
+     *
+     * @return the data
+     */
+    public T getData() {
+        return data;
+    }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/Configuration.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/Configuration.java
@ -0,0 +1,41 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * 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;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", comments = "Generator version: 7.10.0-SNAPSHOT")
+public class Configuration {
+    public static final String VERSION = "1.0.0";
+
+    private static ApiClient defaultApiClient = new ApiClient();
+
+    /**
+     * Get the default API client, which would be used when creating API
+     * instances without providing an API client.
+     *
+     * @return Default API client
+     */
+    public static ApiClient getDefaultApiClient() {
+        return defaultApiClient;
+    }
+
+    /**
+     * Set the default API client, which would be used when creating API
+     * instances without providing an API client.
+     *
+     * @param apiClient API client
+     */
+    public static void setDefaultApiClient(ApiClient apiClient) {
+        defaultApiClient = apiClient;
+    }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/GzipRequestInterceptor.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/GzipRequestInterceptor.java
@ -0,0 +1,85 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client;
+
+import okhttp3.*;
+import okio.Buffer;
+import okio.BufferedSink;
+import okio.GzipSink;
+import okio.Okio;
+
+import java.io.IOException;
+
+/**
+ * Encodes request bodies using gzip.
+ *
+ * Taken from https://github.com/square/okhttp/issues/350
+ */
+class GzipRequestInterceptor implements Interceptor {
+    @Override
+    public Response intercept(Chain chain) throws IOException {
+        Request originalRequest = chain.request();
+        if (originalRequest.body() == null || originalRequest.header("Content-Encoding") != null) {
+            return chain.proceed(originalRequest);
+        }
+
+        Request compressedRequest = originalRequest.newBuilder()
+                                                   .header("Content-Encoding", "gzip")
+                                                   .method(originalRequest.method(), forceContentLength(gzip(originalRequest.body())))
+                                                   .build();
+        return chain.proceed(compressedRequest);
+    }
+
+    private RequestBody forceContentLength(final RequestBody requestBody) throws IOException {
+        final Buffer buffer = new Buffer();
+        requestBody.writeTo(buffer);
+        return new RequestBody() {
+            @Override
+            public MediaType contentType() {
+                return requestBody.contentType();
+            }
+
+            @Override
+            public long contentLength() {
+                return buffer.size();
+            }
+
+            @Override
+            public void writeTo(BufferedSink sink) throws IOException {
+                sink.write(buffer.snapshot());
+            }
+        };
+    }
+
+    private RequestBody gzip(final RequestBody body) {
+        return new RequestBody() {
+            @Override
+            public MediaType contentType() {
+                return body.contentType();
+            }
+
+            @Override
+            public long contentLength() {
+                return -1; // We don't know the compressed length in advance!
+            }
+
+            @Override
+            public void writeTo(BufferedSink sink) throws IOException {
+                BufferedSink gzipSink = Okio.buffer(new GzipSink(sink));
+                body.writeTo(gzipSink);
+                gzipSink.close();
+            }
+        };
+    }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/JSON.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/JSON.java
@ -0,0 +1,400 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonParseException;
+import com.google.gson.TypeAdapter;
+import com.google.gson.internal.bind.util.ISO8601Utils;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+import com.google.gson.JsonElement;
+import io.gsonfire.GsonFireBuilder;
+import io.gsonfire.TypeSelector;
+
+import okio.ByteString;
+
+import java.io.IOException;
+import java.io.StringReader;
+import java.lang.reflect.Type;
+import java.text.DateFormat;
+import java.text.ParseException;
+import java.text.ParsePosition;
+import java.time.LocalDate;
+import java.time.OffsetDateTime;
+import java.time.format.DateTimeFormatter;
+import java.util.Date;
+import java.util.Locale;
+import java.util.Map;
+import java.util.HashMap;
+
+/*
+ * A JSON utility class
+ *
+ * NOTE: in the future, this class may be converted to static, which may break
+ *       backward-compatibility
+ */
+public class JSON {
+    private static Gson gson;
+    private static boolean isLenientOnJson = false;
+    private static DateTypeAdapter dateTypeAdapter = new DateTypeAdapter();
+    private static SqlDateTypeAdapter sqlDateTypeAdapter = new SqlDateTypeAdapter();
+    private static OffsetDateTimeTypeAdapter offsetDateTimeTypeAdapter = new OffsetDateTimeTypeAdapter();
+    private static LocalDateTypeAdapter localDateTypeAdapter = new LocalDateTypeAdapter();
+    private static ByteArrayAdapter byteArrayAdapter = new ByteArrayAdapter();
+
+    @SuppressWarnings("unchecked")
+    public static GsonBuilder createGson() {
+        GsonFireBuilder fireBuilder = new GsonFireBuilder()
+        ;
+        GsonBuilder builder = fireBuilder.createGsonBuilder();
+        return builder;
+    }
+
+    private static String getDiscriminatorValue(JsonElement readElement, String discriminatorField) {
+        JsonElement element = readElement.getAsJsonObject().get(discriminatorField);
+        if (null == element) {
+            throw new IllegalArgumentException("missing discriminator field: <" + discriminatorField + ">");
+        }
+        return element.getAsString();
+    }
+
+    /**
+     * Returns the Java class that implements the OpenAPI schema for the specified discriminator value.
+     *
+     * @param classByDiscriminatorValue The map of discriminator values to Java classes.
+     * @param discriminatorValue The value of the OpenAPI discriminator in the input data.
+     * @return The Java class that implements the OpenAPI schema
+     */
+    private static Class getClassByDiscriminator(Map classByDiscriminatorValue, String discriminatorValue) {
+        Class clazz = (Class) classByDiscriminatorValue.get(discriminatorValue);
+        if (null == clazz) {
+            throw new IllegalArgumentException("cannot determine model class of name: <" + discriminatorValue + ">");
+        }
+        return clazz;
+    }
+
+    static {
+        GsonBuilder gsonBuilder = createGson();
+        gsonBuilder.registerTypeAdapter(Date.class, dateTypeAdapter);
+        gsonBuilder.registerTypeAdapter(java.sql.Date.class, sqlDateTypeAdapter);
+        gsonBuilder.registerTypeAdapter(OffsetDateTime.class, offsetDateTimeTypeAdapter);
+        gsonBuilder.registerTypeAdapter(LocalDate.class, localDateTypeAdapter);
+        gsonBuilder.registerTypeAdapter(byte[].class, byteArrayAdapter);
+        gson = gsonBuilder.create();
+    }
+
+    /**
+     * Get Gson.
+     *
+     * @return Gson
+     */
+    public static Gson getGson() {
+        return gson;
+    }
+
+    /**
+     * Set Gson.
+     *
+     * @param gson Gson
+     */
+    public static void setGson(Gson gson) {
+        JSON.gson = gson;
+    }
+
+    public static void setLenientOnJson(boolean lenientOnJson) {
+        isLenientOnJson = lenientOnJson;
+    }
+
+    /**
+     * Serialize the given Java object into JSON string.
+     *
+     * @param obj Object
+     * @return String representation of the JSON
+     */
+    public static String serialize(Object obj) {
+        return gson.toJson(obj);
+    }
+
+    /**
+     * Deserialize the given JSON string to Java object.
+     *
+     * @param <T>        Type
+     * @param body       The JSON string
+     * @param returnType The type to deserialize into
+     * @return The deserialized Java object
+     */
+    @SuppressWarnings("unchecked")
+    public static <T> T deserialize(String body, Type returnType) {
+        try {
+            if (isLenientOnJson) {
+                JsonReader jsonReader = new JsonReader(new StringReader(body));
+                // see https://google-gson.googlecode.com/svn/trunk/gson/docs/javadocs/com/google/gson/stream/JsonReader.html#setLenient(boolean)
+                jsonReader.setLenient(true);
+                return gson.fromJson(jsonReader, returnType);
+            } else {
+                return gson.fromJson(body, returnType);
+            }
+        } catch (JsonParseException e) {
+            // Fallback processing when failed to parse JSON form response body:
+            // return the response body string directly for the String return type;
+            if (returnType.equals(String.class)) {
+                return (T) body;
+            } else {
+                throw (e);
+            }
+        }
+    }
+
+    /**
+     * Gson TypeAdapter for Byte Array type
+     */
+    public static class ByteArrayAdapter extends TypeAdapter<byte[]> {
+
+        @Override
+        public void write(JsonWriter out, byte[] value) throws IOException {
+            if (value == null) {
+                out.nullValue();
+            } else {
+                out.value(ByteString.of(value).base64());
+            }
+        }
+
+        @Override
+        public byte[] read(JsonReader in) throws IOException {
+            switch (in.peek()) {
+                case NULL:
+                    in.nextNull();
+                    return null;
+                default:
+                    String bytesAsBase64 = in.nextString();
+                    ByteString byteString = ByteString.decodeBase64(bytesAsBase64);
+                    return byteString.toByteArray();
+            }
+        }
+    }
+
+    /**
+     * Gson TypeAdapter for JSR310 OffsetDateTime type
+     */
+    public static class OffsetDateTimeTypeAdapter extends TypeAdapter<OffsetDateTime> {
+
+        private DateTimeFormatter formatter;
+
+        public OffsetDateTimeTypeAdapter() {
+            this(DateTimeFormatter.ISO_OFFSET_DATE_TIME);
+        }
+
+        public OffsetDateTimeTypeAdapter(DateTimeFormatter formatter) {
+            this.formatter = formatter;
+        }
+
+        public void setFormat(DateTimeFormatter dateFormat) {
+            this.formatter = dateFormat;
+        }
+
+        @Override
+        public void write(JsonWriter out, OffsetDateTime date) throws IOException {
+            if (date == null) {
+                out.nullValue();
+            } else {
+                out.value(formatter.format(date));
+            }
+        }
+
+        @Override
+        public OffsetDateTime read(JsonReader in) throws IOException {
+            switch (in.peek()) {
+                case NULL:
+                    in.nextNull();
+                    return null;
+                default:
+                    String date = in.nextString();
+                    if (date.endsWith("+0000")) {
+                        date = date.substring(0, date.length()-5) + "Z";
+                    }
+                    return OffsetDateTime.parse(date, formatter);
+            }
+        }
+    }
+
+    /**
+     * Gson TypeAdapter for JSR310 LocalDate type
+     */
+    public static class LocalDateTypeAdapter extends TypeAdapter<LocalDate> {
+
+        private DateTimeFormatter formatter;
+
+        public LocalDateTypeAdapter() {
+            this(DateTimeFormatter.ISO_LOCAL_DATE);
+        }
+
+        public LocalDateTypeAdapter(DateTimeFormatter formatter) {
+            this.formatter = formatter;
+        }
+
+        public void setFormat(DateTimeFormatter dateFormat) {
+            this.formatter = dateFormat;
+        }
+
+        @Override
+        public void write(JsonWriter out, LocalDate date) throws IOException {
+            if (date == null) {
+                out.nullValue();
+            } else {
+                out.value(formatter.format(date));
+            }
+        }
+
+        @Override
+        public LocalDate read(JsonReader in) throws IOException {
+            switch (in.peek()) {
+                case NULL:
+                    in.nextNull();
+                    return null;
+                default:
+                    String date = in.nextString();
+                    return LocalDate.parse(date, formatter);
+            }
+        }
+    }
+
+    public static void setOffsetDateTimeFormat(DateTimeFormatter dateFormat) {
+        offsetDateTimeTypeAdapter.setFormat(dateFormat);
+    }
+
+    public static void setLocalDateFormat(DateTimeFormatter dateFormat) {
+        localDateTypeAdapter.setFormat(dateFormat);
+    }
+
+    /**
+     * Gson TypeAdapter for java.sql.Date type
+     * If the dateFormat is null, a simple "yyyy-MM-dd" format will be used
+     * (more efficient than SimpleDateFormat).
+     */
+    public static class SqlDateTypeAdapter extends TypeAdapter<java.sql.Date> {
+
+        private DateFormat dateFormat;
+
+        public SqlDateTypeAdapter() {}
+
+        public SqlDateTypeAdapter(DateFormat dateFormat) {
+            this.dateFormat = dateFormat;
+        }
+
+        public void setFormat(DateFormat dateFormat) {
+            this.dateFormat = dateFormat;
+        }
+
+        @Override
+        public void write(JsonWriter out, java.sql.Date date) throws IOException {
+            if (date == null) {
+                out.nullValue();
+            } else {
+                String value;
+                if (dateFormat != null) {
+                    value = dateFormat.format(date);
+                } else {
+                    value = date.toString();
+                }
+                out.value(value);
+            }
+        }
+
+        @Override
+        public java.sql.Date read(JsonReader in) throws IOException {
+            switch (in.peek()) {
+                case NULL:
+                    in.nextNull();
+                    return null;
+                default:
+                    String date = in.nextString();
+                    try {
+                        if (dateFormat != null) {
+                            return new java.sql.Date(dateFormat.parse(date).getTime());
+                        }
+                        return new java.sql.Date(ISO8601Utils.parse(date, new ParsePosition(0)).getTime());
+                    } catch (ParseException e) {
+                        throw new JsonParseException(e);
+                    }
+            }
+        }
+    }
+
+    /**
+     * Gson TypeAdapter for java.util.Date type
+     * If the dateFormat is null, ISO8601Utils will be used.
+     */
+    public static class DateTypeAdapter extends TypeAdapter<Date> {
+
+        private DateFormat dateFormat;
+
+        public DateTypeAdapter() {}
+
+        public DateTypeAdapter(DateFormat dateFormat) {
+            this.dateFormat = dateFormat;
+        }
+
+        public void setFormat(DateFormat dateFormat) {
+            this.dateFormat = dateFormat;
+        }
+
+        @Override
+        public void write(JsonWriter out, Date date) throws IOException {
+            if (date == null) {
+                out.nullValue();
+            } else {
+                String value;
+                if (dateFormat != null) {
+                    value = dateFormat.format(date);
+                } else {
+                    value = ISO8601Utils.format(date, true);
+                }
+                out.value(value);
+            }
+        }
+
+        @Override
+        public Date read(JsonReader in) throws IOException {
+            try {
+                switch (in.peek()) {
+                    case NULL:
+                        in.nextNull();
+                        return null;
+                    default:
+                        String date = in.nextString();
+                        try {
+                            if (dateFormat != null) {
+                                return dateFormat.parse(date);
+                            }
+                            return ISO8601Utils.parse(date, new ParsePosition(0));
+                        } catch (ParseException e) {
+                            throw new JsonParseException(e);
+                        }
+                }
+            } catch (IllegalArgumentException e) {
+                throw new JsonParseException(e);
+            }
+        }
+    }
+
+    public static void setDateFormat(DateFormat dateFormat) {
+        dateTypeAdapter.setFormat(dateFormat);
+    }
+
+    public static void setSqlDateFormat(DateFormat dateFormat) {
+        sqlDateTypeAdapter.setFormat(dateFormat);
+    }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/Pair.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/Pair.java
@ -0,0 +1,57 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * 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;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", comments = "Generator version: 7.10.0-SNAPSHOT")
+public class Pair {
+    private String name = "";
+    private String value = "";
+
+    public Pair (String name, String value) {
+        setName(name);
+        setValue(value);
+    }
+
+    private void setName(String name) {
+        if (!isValidString(name)) {
+            return;
+        }
+
+        this.name = name;
+    }
+
+    private void setValue(String value) {
+        if (!isValidString(value)) {
+            return;
+        }
+
+        this.value = value;
+    }
+
+    public String getName() {
+        return this.name;
+    }
+
+    public String getValue() {
+        return this.value;
+    }
+
+    private boolean isValidString(String arg) {
+        if (arg == null) {
+            return false;
+        }
+
+        return true;
+    }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/ProgressRequestBody.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/ProgressRequestBody.java
@ -0,0 +1,73 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client;
+
+import okhttp3.MediaType;
+import okhttp3.RequestBody;
+
+import java.io.IOException;
+
+import okio.Buffer;
+import okio.BufferedSink;
+import okio.ForwardingSink;
+import okio.Okio;
+import okio.Sink;
+
+public class ProgressRequestBody extends RequestBody {
+
+    private final RequestBody requestBody;
+
+    private final ApiCallback callback;
+
+    public ProgressRequestBody(RequestBody requestBody, ApiCallback callback) {
+        this.requestBody = requestBody;
+        this.callback = callback;
+    }
+
+    @Override
+    public MediaType contentType() {
+        return requestBody.contentType();
+    }
+
+    @Override
+    public long contentLength() throws IOException {
+        return requestBody.contentLength();
+    }
+
+    @Override
+    public void writeTo(BufferedSink sink) throws IOException {
+        BufferedSink bufferedSink = Okio.buffer(sink(sink));
+        requestBody.writeTo(bufferedSink);
+        bufferedSink.flush();
+    }
+
+    private Sink sink(Sink sink) {
+        return new ForwardingSink(sink) {
+
+            long bytesWritten = 0L;
+            long contentLength = 0L;
+
+            @Override
+            public void write(Buffer source, long byteCount) throws IOException {
+                super.write(source, byteCount);
+                if (contentLength == 0) {
+                    contentLength = contentLength();
+                }
+
+                bytesWritten += byteCount;
+                callback.onUploadProgress(bytesWritten, contentLength, bytesWritten == contentLength);
+            }
+        };
+    }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/ProgressResponseBody.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/ProgressResponseBody.java
@ -0,0 +1,70 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client;
+
+import okhttp3.MediaType;
+import okhttp3.ResponseBody;
+
+import java.io.IOException;
+
+import okio.Buffer;
+import okio.BufferedSource;
+import okio.ForwardingSource;
+import okio.Okio;
+import okio.Source;
+
+public class ProgressResponseBody extends ResponseBody {
+
+    private final ResponseBody responseBody;
+    private final ApiCallback callback;
+    private BufferedSource bufferedSource;
+
+    public ProgressResponseBody(ResponseBody responseBody, ApiCallback callback) {
+        this.responseBody = responseBody;
+        this.callback = callback;
+    }
+
+    @Override
+    public MediaType contentType() {
+        return responseBody.contentType();
+    }
+
+    @Override
+    public long contentLength() {
+        return responseBody.contentLength();
+    }
+
+    @Override
+    public BufferedSource source() {
+        if (bufferedSource == null) {
+            bufferedSource = Okio.buffer(source(responseBody.source()));
+        }
+        return bufferedSource;
+    }
+
+    private Source source(Source source) {
+        return new ForwardingSource(source) {
+            long totalBytesRead = 0L;
+
+            @Override
+            public long read(Buffer sink, long byteCount) throws IOException {
+                long bytesRead = super.read(sink, byteCount);
+                // read() returns the number of bytes read, or -1 if this source is exhausted.
+                totalBytesRead += bytesRead != -1 ? bytesRead : 0;
+                callback.onDownloadProgress(totalBytesRead, responseBody.contentLength(), bytesRead == -1);
+                return bytesRead;
+            }
+        };
+    }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/ServerConfiguration.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/ServerConfiguration.java
@ -0,0 +1,72 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", comments = "Generator version: 7.10.0-SNAPSHOT")
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A description of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new IllegalArgumentException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replace("{" + name + "}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/ServerVariable.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/ServerVariable.java
@ -0,0 +1,37 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", comments = "Generator version: 7.10.0-SNAPSHOT")
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/StringUtil.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/StringUtil.java
@ -0,0 +1,83 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client;
+
+import java.util.Collection;
+import java.util.Iterator;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", comments = "Generator version: 7.10.0-SNAPSHOT")
+public class StringUtil {
+  /**
+   * Check if the given array contains the given value (with case-insensitive comparison).
+   *
+   * @param array The array
+   * @param value The value to search
+   * @return true if the array contains the value
+   */
+  public static boolean containsIgnoreCase(String[] array, String value) {
+    for (String str : array) {
+      if (value == null && str == null) {
+        return true;
+      }
+      if (value != null && value.equalsIgnoreCase(str)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  /**
+   * Join an array of strings with the given separator.
+   * <p>
+   * Note: This might be replaced by utility method from commons-lang or guava someday
+   * if one of those libraries is added as dependency.
+   * </p>
+   *
+   * @param array     The array of strings
+   * @param separator The separator
+   * @return the resulting string
+   */
+  public static String join(String[] array, String separator) {
+    int len = array.length;
+    if (len == 0) {
+      return "";
+    }
+
+    StringBuilder out = new StringBuilder();
+    out.append(array[0]);
+    for (int i = 1; i < len; i++) {
+      out.append(separator).append(array[i]);
+    }
+    return out.toString();
+  }
+
+  /**
+   * Join a list of strings with the given separator.
+   *
+   * @param list      The list of strings
+   * @param separator The separator
+   * @return the resulting string
+   */
+  public static String join(Collection<String> list, String separator) {
+    Iterator<String> iterator = list.iterator();
+    StringBuilder out = new StringBuilder();
+    if (iterator.hasNext()) {
+      out.append(iterator.next());
+    }
+    while (iterator.hasNext()) {
+      out.append(separator).append(iterator.next());
+    }
+    return out.toString();
+  }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/api/FakeApi.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/api/FakeApi.java
@ -0,0 +1,187 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * 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 java.lang.reflect.Type;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class FakeApi {
+    private ApiClient localVarApiClient;
+    private int localHostIndex;
+    private String localCustomBaseUrl;
+
+    public FakeApi() {
+        this(Configuration.getDefaultApiClient());
+    }
+
+    public FakeApi(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 getPetById0
+     * @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>  </td><td>  -  </td></tr>
+     </table>
+     */
+    public okhttp3.Call getPetById0Call(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 = "/fake/duplicated/operationId";
+
+        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 getPetById0ValidateBeforeCall(final ApiCallback _callback) throws ApiException {
+        return getPetById0Call(_callback);
+
+    }
+
+    /**
+     * 
+     * 
+     * @return Object
+     * @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>  </td><td>  -  </td></tr>
+     </table>
+     */
+    public Object getPetById0() throws ApiException {
+        ApiResponse<Object> localVarResp = getPetById0WithHttpInfo();
+        return localVarResp.getData();
+    }
+
+    /**
+     * 
+     * 
+     * @return ApiResponse&lt;Object&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>  </td><td>  -  </td></tr>
+     </table>
+     */
+    public ApiResponse<Object> getPetById0WithHttpInfo() throws ApiException {
+        okhttp3.Call localVarCall = getPetById0ValidateBeforeCall(null);
+        Type localVarReturnType = new TypeToken<Object>(){}.getType();
+        return localVarApiClient.execute(localVarCall, localVarReturnType);
+    }
+
+    /**
+     *  (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>  </td><td>  -  </td></tr>
+     </table>
+     */
+    public okhttp3.Call getPetById0Async(final ApiCallback<Object> _callback) throws ApiException {
+
+        okhttp3.Call localVarCall = getPetById0ValidateBeforeCall(_callback);
+        Type localVarReturnType = new TypeToken<Object>(){}.getType();
+        localVarApiClient.executeAsync(localVarCall, localVarReturnType, _callback);
+        return localVarCall;
+    }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/api/PetApi.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/api/PetApi.java
@ -0,0 +1,206 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * 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 java.lang.reflect.Type;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class PetApi {
+    private ApiClient localVarApiClient;
+    private int localHostIndex;
+    private String localCustomBaseUrl;
+
+    public PetApi() {
+        this(Configuration.getDefaultApiClient());
+    }
+
+    public PetApi(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 getPetById
+     * @param petId ID of pet to return (required)
+     * @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 ID supplied </td><td>  -  </td></tr>
+        <tr><td> 404 </td><td> Pet not found </td><td>  -  </td></tr>
+     </table>
+     */
+    public okhttp3.Call getPetByIdCall(Long petId, 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 = "/pet/{petId}"
+            .replace("{" + "petId" + "}", localVarApiClient.escapeString(petId.toString()));
+
+        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/xml",
+            "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[] { "api_key" };
+        return localVarApiClient.buildCall(basePath, localVarPath, "GET", localVarQueryParams, localVarCollectionQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAuthNames, _callback);
+    }
+
+    @SuppressWarnings("rawtypes")
+    private okhttp3.Call getPetByIdValidateBeforeCall(Long petId, final ApiCallback _callback) throws ApiException {
+        // verify the required parameter 'petId' is set
+        if (petId == null) {
+            throw new ApiException("Missing the required parameter 'petId' when calling getPetById(Async)");
+        }
+
+        return getPetByIdCall(petId, _callback);
+
+    }
+
+    /**
+     * Find pet by ID
+     * Returns a single pet
+     * @param petId ID of pet to return (required)
+     * @return Object
+     * @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 ID supplied </td><td>  -  </td></tr>
+        <tr><td> 404 </td><td> Pet not found </td><td>  -  </td></tr>
+     </table>
+     */
+    public Object getPetById(Long petId) throws ApiException {
+        ApiResponse<Object> localVarResp = getPetByIdWithHttpInfo(petId);
+        return localVarResp.getData();
+    }
+
+    /**
+     * Find pet by ID
+     * Returns a single pet
+     * @param petId ID of pet to return (required)
+     * @return ApiResponse&lt;Object&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 ID supplied </td><td>  -  </td></tr>
+        <tr><td> 404 </td><td> Pet not found </td><td>  -  </td></tr>
+     </table>
+     */
+    public ApiResponse<Object> getPetByIdWithHttpInfo(Long petId) throws ApiException {
+        okhttp3.Call localVarCall = getPetByIdValidateBeforeCall(petId, null);
+        Type localVarReturnType = new TypeToken<Object>(){}.getType();
+        return localVarApiClient.execute(localVarCall, localVarReturnType);
+    }
+
+    /**
+     * Find pet by ID (asynchronously)
+     * Returns a single pet
+     * @param petId ID of pet to return (required)
+     * @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 ID supplied </td><td>  -  </td></tr>
+        <tr><td> 404 </td><td> Pet not found </td><td>  -  </td></tr>
+     </table>
+     */
+    public okhttp3.Call getPetByIdAsync(Long petId, final ApiCallback<Object> _callback) throws ApiException {
+
+        okhttp3.Call localVarCall = getPetByIdValidateBeforeCall(petId, _callback);
+        Type localVarReturnType = new TypeToken<Object>(){}.getType();
+        localVarApiClient.executeAsync(localVarCall, localVarReturnType, _callback);
+        return localVarCall;
+    }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/auth/ApiKeyAuth.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/auth/ApiKeyAuth.java
@ -0,0 +1,80 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.auth;
+
+import org.openapitools.client.ApiException;
+import org.openapitools.client.Pair;
+
+import java.net.URI;
+import java.util.Map;
+import java.util.List;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", comments = "Generator version: 7.10.0-SNAPSHOT")
+public class ApiKeyAuth implements Authentication {
+  private final String location;
+  private final String paramName;
+
+  private String apiKey;
+  private String apiKeyPrefix;
+
+  public ApiKeyAuth(String location, String paramName) {
+    this.location = location;
+    this.paramName = paramName;
+  }
+
+  public String getLocation() {
+    return location;
+  }
+
+  public String getParamName() {
+    return paramName;
+  }
+
+  public String getApiKey() {
+    return apiKey;
+  }
+
+  public void setApiKey(String apiKey) {
+    this.apiKey = apiKey;
+  }
+
+  public String getApiKeyPrefix() {
+    return apiKeyPrefix;
+  }
+
+  public void setApiKeyPrefix(String apiKeyPrefix) {
+    this.apiKeyPrefix = apiKeyPrefix;
+  }
+
+  @Override
+  public void applyToParams(List<Pair> queryParams, Map<String, String> headerParams, Map<String, String> cookieParams,
+                           String payload, String method, URI uri) throws ApiException {
+    if (apiKey == null) {
+      return;
+    }
+    String value;
+    if (apiKeyPrefix != null) {
+      value = apiKeyPrefix + " " + apiKey;
+    } else {
+      value = apiKey;
+    }
+    if ("query".equals(location)) {
+      queryParams.add(new Pair(paramName, value));
+    } else if ("header".equals(location)) {
+      headerParams.put(paramName, value);
+    } else if ("cookie".equals(location)) {
+      cookieParams.put(paramName, value);
+    }
+  }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/auth/Authentication.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/auth/Authentication.java
@ -0,0 +1,36 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.auth;
+
+import org.openapitools.client.Pair;
+import org.openapitools.client.ApiException;
+
+import java.net.URI;
+import java.util.Map;
+import java.util.List;
+
+public interface Authentication {
+    /**
+     * Apply authentication settings to header and query params.
+     *
+     * @param queryParams List of query parameters
+     * @param headerParams Map of header parameters
+     * @param cookieParams Map of cookie parameters
+     * @param payload HTTP request body
+     * @param method HTTP method
+     * @param uri URI
+     * @throws ApiException if failed to update the parameters
+     */
+    void applyToParams(List<Pair> queryParams, Map<String, String> headerParams, Map<String, String> cookieParams, String payload, String method, URI uri) throws ApiException;
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/auth/HttpBasicAuth.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/auth/HttpBasicAuth.java
@ -0,0 +1,55 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.auth;
+
+import org.openapitools.client.Pair;
+import org.openapitools.client.ApiException;
+
+import okhttp3.Credentials;
+
+import java.net.URI;
+import java.util.Map;
+import java.util.List;
+
+public class HttpBasicAuth implements Authentication {
+    private String username;
+    private String password;
+
+    public String getUsername() {
+        return username;
+    }
+
+    public void setUsername(String username) {
+        this.username = username;
+    }
+
+    public String getPassword() {
+        return password;
+    }
+
+    public void setPassword(String password) {
+        this.password = password;
+    }
+
+    @Override
+    public void applyToParams(List<Pair> queryParams, Map<String, String> headerParams, Map<String, String> cookieParams,
+                              String payload, String method, URI uri) throws ApiException {
+        if (username == null && password == null) {
+            return;
+        }
+        headerParams.put("Authorization", Credentials.basic(
+            username == null ? "" : username,
+            password == null ? "" : password));
+    }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/auth/HttpBearerAuth.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/auth/HttpBearerAuth.java
@ -0,0 +1,75 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.auth;
+
+import org.openapitools.client.ApiException;
+import org.openapitools.client.Pair;
+
+import java.net.URI;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.function.Supplier;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", comments = "Generator version: 7.10.0-SNAPSHOT")
+public class HttpBearerAuth implements Authentication {
+  private final String scheme;
+  private Supplier<String> tokenSupplier;
+
+  public HttpBearerAuth(String scheme) {
+    this.scheme = scheme;
+  }
+
+  /**
+   * Gets the token, which together with the scheme, will be sent as the value of the Authorization header.
+   *
+   * @return The bearer token
+   */
+  public String getBearerToken() {
+    return tokenSupplier.get();
+  }
+
+  /**
+   * Sets the token, which together with the scheme, will be sent as the value of the Authorization header.
+   *
+   * @param bearerToken The bearer token to send in the Authorization header
+   */
+  public void setBearerToken(String bearerToken) {
+    this.tokenSupplier = () -> bearerToken;
+  }
+
+  /**
+   * Sets the supplier of tokens, which together with the scheme, will be sent as the value of the Authorization header.
+   *
+   * @param tokenSupplier The supplier of bearer tokens to send in the Authorization header
+   */
+  public void setBearerToken(Supplier<String> tokenSupplier) {
+    this.tokenSupplier = tokenSupplier;
+  }
+
+  @Override
+  public void applyToParams(List<Pair> queryParams, Map<String, String> headerParams, Map<String, String> cookieParams,
+                            String payload, String method, URI uri) throws ApiException {
+    String bearerToken = Optional.ofNullable(tokenSupplier).map(Supplier::get).orElse(null);
+    if (bearerToken == null) {
+      return;
+    }
+
+    headerParams.put("Authorization", (scheme != null ? upperCaseBearer(scheme) + " " : "") + bearerToken);
+  }
+
+  private static String upperCaseBearer(String scheme) {
+    return ("bearer".equalsIgnoreCase(scheme)) ? "Bearer" : scheme;
+  }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/auth/OAuth.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/auth/OAuth.java
@ -0,0 +1,42 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.auth;
+
+import org.openapitools.client.Pair;
+import org.openapitools.client.ApiException;
+
+import java.net.URI;
+import java.util.Map;
+import java.util.List;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", comments = "Generator version: 7.10.0-SNAPSHOT")
+public class OAuth implements Authentication {
+  private String accessToken;
+
+  public String getAccessToken() {
+    return accessToken;
+  }
+
+  public void setAccessToken(String accessToken) {
+    this.accessToken = accessToken;
+  }
+
+  @Override
+  public void applyToParams(List<Pair> queryParams, Map<String, String> headerParams, Map<String, String> cookieParams,
+                            String payload, String method, URI uri) throws ApiException {
+    if (accessToken != null) {
+      headerParams.put("Authorization", "Bearer " + accessToken);
+    }
+  }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/auth/OAuthFlow.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/auth/OAuthFlow.java
@ -0,0 +1,25 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.auth;
+
+/**
+ * OAuth flows that are supported by this client
+ */
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", comments = "Generator version: 7.10.0-SNAPSHOT")
+public enum OAuthFlow {
+    ACCESS_CODE, //called authorizationCode  in OpenAPI 3.0
+    IMPLICIT,
+    PASSWORD,
+    APPLICATION //called clientCredentials in OpenAPI 3.0
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/auth/OAuthOkHttpClient.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/auth/OAuthOkHttpClient.java
@ -0,0 +1,82 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.auth;
+
+import okhttp3.OkHttpClient;
+import okhttp3.MediaType;
+import okhttp3.Request;
+import okhttp3.RequestBody;
+import okhttp3.Response;
+
+import org.apache.oltu.oauth2.client.HttpClient;
+import org.apache.oltu.oauth2.client.request.OAuthClientRequest;
+import org.apache.oltu.oauth2.client.response.OAuthClientResponse;
+import org.apache.oltu.oauth2.client.response.OAuthClientResponseFactory;
+import org.apache.oltu.oauth2.common.exception.OAuthProblemException;
+import org.apache.oltu.oauth2.common.exception.OAuthSystemException;
+
+import java.io.IOException;
+import java.util.Map;
+import java.util.Map.Entry;
+
+public class OAuthOkHttpClient implements HttpClient {
+    private OkHttpClient client;
+
+    public OAuthOkHttpClient() {
+        this.client = new OkHttpClient();
+    }
+
+    public OAuthOkHttpClient(OkHttpClient client) {
+        this.client = client;
+    }
+
+    @Override
+    public <T extends OAuthClientResponse> T execute(OAuthClientRequest request, Map<String, String> headers,
+                                                     String requestMethod, Class<T> responseClass)
+            throws OAuthSystemException, OAuthProblemException {
+
+        MediaType mediaType = MediaType.parse("application/json");
+        Request.Builder requestBuilder = new Request.Builder().url(request.getLocationUri());
+
+        if(headers != null) {
+            for (Entry<String, String> entry : headers.entrySet()) {
+                if (entry.getKey().equalsIgnoreCase("Content-Type")) {
+                    mediaType = MediaType.parse(entry.getValue());
+                } else {
+                    requestBuilder.addHeader(entry.getKey(), entry.getValue());
+                }
+            }
+        }
+
+        RequestBody body = request.getBody() != null ? RequestBody.create(request.getBody(), mediaType) : null;
+        requestBuilder.method(requestMethod, body);
+
+        try {
+            Response response = client.newCall(requestBuilder.build()).execute();
+            return OAuthClientResponseFactory.createCustomResponse(
+                    response.body().string(),
+                    response.body().contentType().toString(),
+                    response.code(),
+                    response.headers().toMultimap(),
+                    responseClass);
+        } catch (IOException e) {
+            throw new OAuthSystemException(e);
+        }
+    }
+
+    @Override
+    public void shutdown() {
+        // Nothing to do here
+    }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/auth/RetryingOAuth.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/auth/RetryingOAuth.java
@ -0,0 +1,223 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.auth;
+
+import org.openapitools.client.ApiException;
+import org.openapitools.client.Pair;
+
+import okhttp3.Interceptor;
+import okhttp3.OkHttpClient;
+import okhttp3.Request;
+import okhttp3.Response;
+
+import org.apache.oltu.oauth2.client.OAuthClient;
+import org.apache.oltu.oauth2.client.request.OAuthBearerClientRequest;
+import org.apache.oltu.oauth2.client.request.OAuthClientRequest;
+import org.apache.oltu.oauth2.client.request.OAuthClientRequest.TokenRequestBuilder;
+import org.apache.oltu.oauth2.client.response.OAuthJSONAccessTokenResponse;
+import org.apache.oltu.oauth2.common.exception.OAuthProblemException;
+import org.apache.oltu.oauth2.common.exception.OAuthSystemException;
+import org.apache.oltu.oauth2.common.message.types.GrantType;
+
+import java.io.IOException;
+import java.net.HttpURLConnection;
+import java.net.URI;
+import java.util.Map;
+import java.util.List;
+
+public class RetryingOAuth extends OAuth implements Interceptor {
+    private OAuthClient oAuthClient;
+
+    private TokenRequestBuilder tokenRequestBuilder;
+
+    /**
+     * @param client An OkHttp client
+     * @param tokenRequestBuilder A token request builder
+     */
+    public RetryingOAuth(OkHttpClient client, TokenRequestBuilder tokenRequestBuilder) {
+        this.oAuthClient = new OAuthClient(new OAuthOkHttpClient(client));
+        this.tokenRequestBuilder = tokenRequestBuilder;
+    }
+
+    /**
+     * @param tokenRequestBuilder A token request builder
+     */
+    public RetryingOAuth(TokenRequestBuilder tokenRequestBuilder) {
+        this(new OkHttpClient(), tokenRequestBuilder);
+    }
+
+    /**
+     * @param tokenUrl The token URL to be used for this OAuth2 flow.
+     *   Applicable to the following OAuth2 flows: "password", "clientCredentials" and "authorizationCode".
+     *   The value must be an absolute URL.
+     * @param clientId The OAuth2 client ID for the "clientCredentials" flow.
+     * @param flow OAuth flow.
+     * @param clientSecret The OAuth2 client secret for the "clientCredentials" flow.
+     * @param parameters A map of string.
+     */
+    public RetryingOAuth(
+            String tokenUrl,
+            String clientId,
+            OAuthFlow flow,
+            String clientSecret,
+            Map<String, String> parameters
+    ) {
+        this(OAuthClientRequest.tokenLocation(tokenUrl)
+                .setClientId(clientId)
+                .setClientSecret(clientSecret));
+        setFlow(flow);
+        if (parameters != null) {
+            for (Map.Entry<String, String> entry : parameters.entrySet()) {
+                tokenRequestBuilder.setParameter(entry.getKey(), entry.getValue());
+            }
+        }
+    }
+
+    /**
+     * Set the OAuth flow
+     *
+     * @param flow The OAuth flow.
+     */
+    public void setFlow(OAuthFlow flow) {
+        switch(flow) {
+            case ACCESS_CODE:
+                tokenRequestBuilder.setGrantType(GrantType.AUTHORIZATION_CODE);
+                break;
+            case IMPLICIT:
+                tokenRequestBuilder.setGrantType(GrantType.IMPLICIT);
+                break;
+            case PASSWORD:
+                tokenRequestBuilder.setGrantType(GrantType.PASSWORD);
+                break;
+            case APPLICATION:
+                tokenRequestBuilder.setGrantType(GrantType.CLIENT_CREDENTIALS);
+                break;
+            default:
+                break;
+        }
+    }
+
+    @Override
+    public Response intercept(Chain chain) throws IOException {
+        return retryingIntercept(chain, true);
+    }
+
+    private Response retryingIntercept(Chain chain, boolean updateTokenAndRetryOnAuthorizationFailure) throws IOException {
+        Request request = chain.request();
+
+        // If the request already has an authorization (e.g. Basic auth), proceed with the request as is
+        if (request.header("Authorization") != null) {
+            return chain.proceed(request);
+        }
+
+        // Get the token if it has not yet been acquired
+        if (getAccessToken() == null) {
+            updateAccessToken(null);
+        }
+
+        OAuthClientRequest oAuthRequest;
+        if (getAccessToken() != null) {
+            // Build the request
+            Request.Builder requestBuilder = request.newBuilder();
+
+            String requestAccessToken = getAccessToken();
+            try {
+                oAuthRequest =
+                        new OAuthBearerClientRequest(request.url().toString()).
+                                setAccessToken(requestAccessToken).
+                                buildHeaderMessage();
+            } catch (OAuthSystemException e) {
+                throw new IOException(e);
+            }
+
+            Map<String, String> headers = oAuthRequest.getHeaders();
+            for (Map.Entry<String, String> entry : headers.entrySet()) {
+                requestBuilder.addHeader(entry.getKey(), entry.getValue());
+            }
+            requestBuilder.url(oAuthRequest.getLocationUri());
+
+            // Execute the request
+            Response response = chain.proceed(requestBuilder.build());
+
+            // 401/403 response codes most likely indicate an expired access token, unless it happens two times in a row
+            if (
+                    response != null &&
+                            (   response.code() == HttpURLConnection.HTTP_UNAUTHORIZED ||
+                                    response.code() == HttpURLConnection.HTTP_FORBIDDEN     ) &&
+                            updateTokenAndRetryOnAuthorizationFailure
+            ) {
+                try {
+                    if (updateAccessToken(requestAccessToken)) {
+                        response.body().close();
+                        return retryingIntercept(chain, false);
+                    }
+                } catch (Exception e) {
+                    response.body().close();
+                    throw e;
+                }
+            }
+            return response;
+        }
+        else {
+            return chain.proceed(chain.request());
+        }
+    }
+
+    /**
+     * Returns true if the access token has been updated
+     *
+     * @param requestAccessToken the request access token
+     * @return True if the update is successful
+     * @throws java.io.IOException If fail to update the access token
+     */
+    public synchronized boolean updateAccessToken(String requestAccessToken) throws IOException {
+        if (getAccessToken() == null || getAccessToken().equals(requestAccessToken)) {
+            try {
+                OAuthJSONAccessTokenResponse accessTokenResponse =
+                        oAuthClient.accessToken(tokenRequestBuilder.buildBodyMessage());
+                if (accessTokenResponse != null && accessTokenResponse.getAccessToken() != null) {
+                    setAccessToken(accessTokenResponse.getAccessToken());
+                }
+            } catch (OAuthSystemException | OAuthProblemException e) {
+                throw new IOException(e);
+            }
+        }
+        return getAccessToken() == null || !getAccessToken().equals(requestAccessToken);
+    }
+
+    /**
+     * Gets the token request builder
+     *
+     * @return A token request builder
+     */
+    public TokenRequestBuilder getTokenRequestBuilder() {
+        return tokenRequestBuilder;
+    }
+
+    /**
+     * Sets the token request builder
+     *
+     * @param tokenRequestBuilder Token request builder
+     */
+    public void setTokenRequestBuilder(TokenRequestBuilder tokenRequestBuilder) {
+        this.tokenRequestBuilder = tokenRequestBuilder;
+    }
+
+    // Applying authorization to parameters is performed in the retryingIntercept method
+    @Override
+    public void applyToParams(List<Pair> queryParams, Map<String, String> headerParams, Map<String, String> cookieParams,
+                             String payload, String method, URI uri) throws ApiException {
+        // No implementation necessary
+    }
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/model/AbstractOpenApiSchema.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/main/java/org/openapitools/client/model/AbstractOpenApiSchema.java
@ -0,0 +1,146 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * 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.ApiException;
+import java.util.Objects;
+import java.lang.reflect.Type;
+import java.util.Map;
+
+/**
+ * Abstract class for oneOf,anyOf schemas defined in OpenAPI spec
+ */
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", comments = "Generator version: 7.10.0-SNAPSHOT")
+public abstract class AbstractOpenApiSchema {
+
+    // store the actual instance of the schema/object
+    private Object instance;
+
+    // is nullable
+    private Boolean isNullable;
+
+    // schema type (e.g. oneOf, anyOf)
+    private final String schemaType;
+
+    public AbstractOpenApiSchema(String schemaType, Boolean isNullable) {
+        this.schemaType = schemaType;
+        this.isNullable = isNullable;
+    }
+
+    /**
+     * Get the list of oneOf/anyOf composed schemas allowed to be stored in this object
+     *
+     * @return an instance of the actual schema/object
+     */
+    public abstract Map<String, Class<?>> getSchemas();
+
+    /**
+     * Get the actual instance
+     *
+     * @return an instance of the actual schema/object
+     */
+    //@JsonValue
+    public Object getActualInstance() {return instance;}
+
+    /**
+     * Set the actual instance
+     *
+     * @param instance the actual instance of the schema/object
+     */
+    public void setActualInstance(Object instance) {this.instance = instance;}
+
+    /**
+     * Get the instant recursively when the schemas defined in oneOf/anyof happen to be oneOf/anyOf schema as well
+     *
+     * @return an instance of the actual schema/object
+     */
+    public Object getActualInstanceRecursively() {
+        return getActualInstanceRecursively(this);
+    }
+
+    private Object getActualInstanceRecursively(AbstractOpenApiSchema object) {
+        if (object.getActualInstance() == null) {
+            return null;
+        } else if (object.getActualInstance() instanceof AbstractOpenApiSchema) {
+            return getActualInstanceRecursively((AbstractOpenApiSchema)object.getActualInstance());
+        } else {
+            return object.getActualInstance();
+        }
+    }
+
+    /**
+     * Get the schema type (e.g. anyOf, oneOf)
+     *
+     * @return the schema type
+     */
+    public String getSchemaType() {
+        return schemaType;
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder sb = new StringBuilder();
+        sb.append("class ").append(getClass()).append(" {\n");
+        sb.append("    instance: ").append(toIndentedString(instance)).append("\n");
+        sb.append("    isNullable: ").append(toIndentedString(isNullable)).append("\n");
+        sb.append("    schemaType: ").append(toIndentedString(schemaType)).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 boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        AbstractOpenApiSchema a = (AbstractOpenApiSchema) o;
+        return Objects.equals(this.instance, a.instance) &&
+            Objects.equals(this.isNullable, a.isNullable) &&
+            Objects.equals(this.schemaType, a.schemaType);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(instance, isNullable, schemaType);
+    }
+
+    /**
+     * Is nullable
+     *
+     * @return true if it's nullable
+     */
+    public Boolean isNullable() {
+        if (Boolean.TRUE.equals(isNullable)) {
+            return Boolean.TRUE;
+        } else {
+            return Boolean.FALSE;
+        }
+    }
+
+
+
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/test/java/org/openapitools/client/api/FakeApiTest.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/test/java/org/openapitools/client/api/FakeApiTest.java
@ -0,0 +1,42 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * 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.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 FakeApi
+ */
+@Disabled
+public class FakeApiTest {
+
+    private final FakeApi api = new FakeApi();
+
+    /**
+     * @throws ApiException if the Api call fails
+     */
+    @Test
+    public void getPetById0Test() throws ApiException {
+        Object response = api.getPetById0();
+        // TODO: test validations
+    }
+
+}
--- a/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/test/java/org/openapitools/client/api/PetApiTest.java
+++ b/samples/client/petstore/java/okhttp-gson-3.1-duplicated-operationid/src/test/java/org/openapitools/client/api/PetApiTest.java
@ -0,0 +1,47 @@
+/*
+ * OpenAPI Petstore
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * 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.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 PetApi
+ */
+@Disabled
+public class PetApiTest {
+
+    private final PetApi api = new PetApi();
+
+    /**
+     * Find pet by ID
+     *
+     * Returns a single pet
+     *
+     * @throws ApiException if the Api call fails
+     */
+    @Test
+    public void getPetByIdTest() throws ApiException {
+        Long petId = null;
+        Object response = api.getPetById(petId);
+        // TODO: test validations
+    }
+
+}
				`@ -0,0 +1 @@`
				`rootProject.name = "petstore-okhttp-gson-31-do"`