Fix query parameters encoding in Java apache-httpclient (#14195)

* fix query parameters encoding in java apache-httpclient

* rearrange tests

* add new files

.github/workflows/samples-java-client-echo-api-jdk11.yaml

@@ -16,6 +16,7 @@ jobs:
       matrix:
         sample:
           # clients
+          - samples/client/echo_api/java/apache-httpclient
           - samples/client/echo_api/java/native
     steps:
       - uses: actions/checkout@v3

bin/configs/java-apache-httpclient-echo-api.yaml

@@ -0,0 +1,8 @@
+generatorName: java
+outputDir: samples/client/echo_api/java/apache-httpclient
+library: apache-httpclient
+inputSpec: modules/openapi-generator/src/test/resources/3_0/echo_api.yaml
+templateDir: modules/openapi-generator/src/main/resources/Java
+additionalProperties:
+  artifactId: echo-api-apache-httpclient
+  hideGenerationTimestamp: "true"

modules/openapi-generator/src/main/resources/Java/libraries/apache-httpclient/ApiClient.mustache

@@ -580,9 +580,11 @@ public class ApiClient{{#jsr310}} extends JavaTimeFormatter{{/jsr310}} {
     List<Pair> params = new ArrayList<Pair>();
 
     // preconditions
-    if (name == null || name.isEmpty() || value == null || value instanceof Collection) return params;
+    if (name == null || name.isEmpty() || value == null || value instanceof Collection) {
+      return params;
+    }
 
-    params.add(new Pair(name, parameterToString(value)));
+    params.add(new Pair(name, escapeString(parameterToString(value))));
     return params;
   }
 
@@ -829,6 +831,10 @@ public class ApiClient{{#jsr310}} extends JavaTimeFormatter{{/jsr310}} {
     if (mimeType == null || isJsonMime(mimeType)) {
       // Assume json if no mime type
       return objectMapper.readValue(entity.getContent(), valueType);
+    } else if ("text/plain".equalsIgnoreCase(mimeType)) {
+      // convert input stream to string
+      java.util.Scanner s = new java.util.Scanner(entity.getContent()).useDelimiter("\\A");
+      return (T) (s.hasNext() ? s.next() : "");
     } else {
       throw new ApiException(
           "Deserialization for content type '" + mimeType + "' not supported for type '" + valueType + "'",
@@ -917,7 +923,8 @@ public class ApiClient{{#jsr310}} extends JavaTimeFormatter{{/jsr310}} {
             url.append("&");
           }
           String value = parameterToString(param.getValue());
-          url.append(escapeString(param.getName())).append("=").append(escapeString(value));
+          // query parameter value already escaped as part of parameterToPair
+          url.append(escapeString(param.getName())).append("=").append(value);
         }
       }
     }

modules/openapi-generator/src/test/resources/3_0/echo_api.yaml

@@ -26,6 +26,66 @@ info:
 servers:
   - url: http://localhost:3000/
 paths:
+  # path parameter tests
+  /path/string/{path_string}/integer/{path_integer}:
+    get:
+      tags:
+        - path 
+      summary: Test path parameter(s)
+      description: Test path parameter(s)
+      operationId: tests/path/string/{path_string}/integer/{path_integer}
+      parameters:
+      - in: path 
+        name: path_string
+        required: true
+        schema:
+          type: string
+      - in: path 
+        name: path_integer
+        required: true
+        schema:
+          type: integer 
+      responses:
+        '200':
+          description: Successful operation
+          content:
+            text/plain:
+              schema:
+                type: string
+  # query parameter tests
+  /query/integer/boolean/string:
+    get:
+      tags:
+        - query
+      summary: Test query parameter(s)
+      description: Test query parameter(s)
+      operationId: test/query/integer/boolean/string
+      parameters:
+      - in: query
+        name: integer_query 
+        style: form #default
+        explode: true #default
+        schema:
+          type: integer
+      - in: query
+        name: boolean_query 
+        style: form #default
+        explode: true #default
+        schema:
+          type: boolean
+      - in: query
+        name: string_query 
+        style: form #default
+        explode: true #default
+        schema:
+          type: string
+      responses:
+        '200':
+          description: Successful operation
+          content:
+            text/plain:
+              schema:
+                type: string
   /query/style_form/explode_true/array_string:
     get:
       tags:

samples/client/echo_api/java/apache-httpclient/.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 Echo Server API
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        java: [ '8' ]
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up JDK
+      uses: actions/setup-java@v2
+      with:
+        java-version: ${{ matrix.java }}
+        distribution: 'temurin'
+        cache: maven
+    - name: Build with Maven
+      run: mvn -B package --no-transfer-progress --file pom.xml

samples/client/echo_api/java/apache-httpclient/.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

samples/client/echo_api/java/apache-httpclient/.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

samples/client/echo_api/java/apache-httpclient/.openapi-generator/FILES

@@ -0,0 +1,41 @@
+.github/workflows/maven.yml
+.gitignore
+.travis.yml
+README.md
+api/openapi.yaml
+build.gradle
+build.sbt
+docs/Category.md
+docs/PathApi.md
+docs/Pet.md
+docs/QueryApi.md
+docs/Tag.md
+docs/TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter.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/ApiClient.java
+src/main/java/org/openapitools/client/ApiException.java
+src/main/java/org/openapitools/client/Configuration.java
+src/main/java/org/openapitools/client/JavaTimeFormatter.java
+src/main/java/org/openapitools/client/Pair.java
+src/main/java/org/openapitools/client/RFC3339DateFormat.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/PathApi.java
+src/main/java/org/openapitools/client/api/QueryApi.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/model/Category.java
+src/main/java/org/openapitools/client/model/Pet.java
+src/main/java/org/openapitools/client/model/Tag.java
+src/main/java/org/openapitools/client/model/TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter.java

samples/client/echo_api/java/apache-httpclient/.openapi-generator/VERSION

@@ -0,0 +1 @@
+6.3.0-SNAPSHOT

samples/client/echo_api/java/apache-httpclient/.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

samples/client/echo_api/java/apache-httpclient/README.md

@@ -0,0 +1,136 @@
+# echo-api-apache-httpclient
+
+Echo Server API
+
+- API version: 0.1.0
+
+Echo Server API
+
+
+*Automatically generated by the [OpenAPI Generator](https://openapi-generator.tech)*
+
+## Requirements
+
+Building the API client library requires:
+
+1. Java 1.8+
+2. Maven/Gradle
+
+## 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>echo-api-apache-httpclient</artifactId>
+  <version>0.1.0</version>
+  <scope>compile</scope>
+</dependency>
+```
+
+### Gradle users
+
+Add this dependency to your project's build file:
+
+```groovy
+compile "org.openapitools:echo-api-apache-httpclient:0.1.0"
+```
+
+### Others
+
+At first generate the JAR by executing:
+
+```shell
+mvn clean package
+```
+
+Then manually install the following JARs:
+
+- `target/echo-api-apache-httpclient-0.1.0.jar`
+- `target/lib/*.jar`
+
+## Getting Started
+
+Please follow the [installation](#installation) instruction and execute the following Java code:
+
+```java
+
+import org.openapitools.client.*;
+import org.openapitools.client.auth.*;
+import org.openapitools.client.model.*;
+import org.openapitools.client.api.PathApi;
+
+public class PathApiExample {
+
+    public static void main(String[] args) {
+        ApiClient defaultClient = Configuration.getDefaultApiClient();
+        defaultClient.setBasePath("http://localhost:3000");
+        
+        PathApi apiInstance = new PathApi(defaultClient);
+        String pathString = "pathString_example"; // String | 
+        Integer pathInteger = 56; // Integer | 
+        try {
+            String result = apiInstance.testsPathStringPathStringIntegerPathInteger(pathString, pathInteger);
+            System.out.println(result);
+        } catch (ApiException e) {
+            System.err.println("Exception when calling PathApi#testsPathStringPathStringIntegerPathInteger");
+            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://localhost:3000*
+
+Class | Method | HTTP request | Description
+------------ | ------------- | ------------- | -------------
+*PathApi* | [**testsPathStringPathStringIntegerPathInteger**](docs/PathApi.md#testsPathStringPathStringIntegerPathInteger) | **GET** /path/string/{path_string}/integer/{path_integer} | Test path parameter(s)
+*QueryApi* | [**testQueryIntegerBooleanString**](docs/QueryApi.md#testQueryIntegerBooleanString) | **GET** /query/integer/boolean/string | Test query parameter(s)
+*QueryApi* | [**testQueryStyleFormExplodeTrueArrayString**](docs/QueryApi.md#testQueryStyleFormExplodeTrueArrayString) | **GET** /query/style_form/explode_true/array_string | Test query parameter(s)
+*QueryApi* | [**testQueryStyleFormExplodeTrueObject**](docs/QueryApi.md#testQueryStyleFormExplodeTrueObject) | **GET** /query/style_form/explode_true/object | Test query parameter(s)
+
+
+## Documentation for Models
+
+ - [Category](docs/Category.md)
+ - [Pet](docs/Pet.md)
+ - [Tag](docs/Tag.md)
+ - [TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter](docs/TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter.md)
+
+
+## Documentation for Authorization
+
+All endpoints do not require authorization.
+Authentication schemes defined for the API:
+
+## Recommendation
+
+It's recommended to create an instance of `ApiClient` per thread in a multithreaded environment to avoid any potential issues.
+
+## Author
+
+team@openapitools.org
+

samples/client/echo_api/java/apache-httpclient/api/openapi.yaml

@@ -0,0 +1,196 @@
+openapi: 3.0.3
+info:
+  contact:
+    email: team@openapitools.org
+  description: Echo Server API
+  license:
+    name: Apache 2.0
+    url: http://www.apache.org/licenses/LICENSE-2.0.html
+  title: Echo Server API
+  version: 0.1.0
+servers:
+- url: http://localhost:3000/
+paths:
+  /path/string/{path_string}/integer/{path_integer}:
+    get:
+      description: Test path parameter(s)
+      operationId: "tests/path/string/{path_string}/integer/{path_integer}"
+      parameters:
+      - explode: false
+        in: path
+        name: path_string
+        required: true
+        schema:
+          type: string
+        style: simple
+      - explode: false
+        in: path
+        name: path_integer
+        required: true
+        schema:
+          type: integer
+        style: simple
+      responses:
+        "200":
+          content:
+            text/plain:
+              schema:
+                type: string
+          description: Successful operation
+      summary: Test path parameter(s)
+      tags:
+      - path
+      x-accepts: text/plain
+  /query/integer/boolean/string:
+    get:
+      description: Test query parameter(s)
+      operationId: test/query/integer/boolean/string
+      parameters:
+      - explode: true
+        in: query
+        name: integer_query
+        required: false
+        schema:
+          type: integer
+        style: form
+      - explode: true
+        in: query
+        name: boolean_query
+        required: false
+        schema:
+          type: boolean
+        style: form
+      - explode: true
+        in: query
+        name: string_query
+        required: false
+        schema:
+          type: string
+        style: form
+      responses:
+        "200":
+          content:
+            text/plain:
+              schema:
+                type: string
+          description: Successful operation
+      summary: Test query parameter(s)
+      tags:
+      - query
+      x-accepts: text/plain
+  /query/style_form/explode_true/array_string:
+    get:
+      description: Test query parameter(s)
+      operationId: test/query/style_form/explode_true/array_string
+      parameters:
+      - explode: true
+        in: query
+        name: query_object
+        required: false
+        schema:
+          $ref: '#/components/schemas/test_query_style_form_explode_true_array_string_query_object_parameter'
+        style: form
+      responses:
+        "200":
+          content:
+            text/plain:
+              schema:
+                type: string
+          description: Successful operation
+      summary: Test query parameter(s)
+      tags:
+      - query
+      x-accepts: text/plain
+  /query/style_form/explode_true/object:
+    get:
+      description: Test query parameter(s)
+      operationId: test/query/style_form/explode_true/object
+      parameters:
+      - explode: true
+        in: query
+        name: query_object
+        required: false
+        schema:
+          $ref: '#/components/schemas/Pet'
+        style: form
+      responses:
+        "200":
+          content:
+            text/plain:
+              schema:
+                type: string
+          description: Successful operation
+      summary: Test query parameter(s)
+      tags:
+      - query
+      x-accepts: text/plain
+components:
+  schemas:
+    Category:
+      properties:
+        id:
+          example: 1
+          format: int64
+          type: integer
+        name:
+          example: Dogs
+          type: string
+      type: object
+      xml:
+        name: category
+    Tag:
+      properties:
+        id:
+          format: int64
+          type: integer
+        name:
+          type: string
+      type: object
+      xml:
+        name: tag
+    Pet:
+      properties:
+        id:
+          example: 10
+          format: int64
+          type: integer
+        name:
+          example: doggie
+          type: string
+        category:
+          $ref: '#/components/schemas/Category'
+        photoUrls:
+          items:
+            type: string
+            xml:
+              name: photoUrl
+          type: array
+          xml:
+            wrapped: true
+        tags:
+          items:
+            $ref: '#/components/schemas/Tag'
+          type: array
+          xml:
+            wrapped: true
+        status:
+          description: pet status in the store
+          enum:
+          - available
+          - pending
+          - sold
+          type: string
+      required:
+      - name
+      - photoUrls
+      type: object
+      xml:
+        name: pet
+    test_query_style_form_explode_true_array_string_query_object_parameter:
+      properties:
+        values:
+          items:
+            type: string
+          type: array
+      type: object
+

samples/client/echo_api/java/apache-httpclient/build.gradle

@@ -0,0 +1,139 @@
+apply plugin: 'idea'
+apply plugin: 'eclipse'
+
+group = 'org.openapitools'
+version = '0.1.0'
+
+buildscript {
+    repositories {
+        mavenCentral()
+    }
+    dependencies {
+        classpath 'com.android.tools.build:gradle:2.3.+'
+        classpath 'com.github.dcendents:android-maven-gradle-plugin:1.5'
+    }
+}
+
+repositories {
+    mavenCentral()
+}
+
+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 ${variant.name}"
+            task.dependsOn variant.javaCompile
+            task.from variant.javaCompile.destinationDir
+            task.destinationDir = project.file("${project.buildDir}/outputs/jar")
+            task.archiveName = "${project.name}-${variant.baseName}-${version}.jar"
+            artifacts.add('archives', task);
+        }
+    }
+
+    task sourcesJar(type: Jar) {
+        from android.sourceSets.main.java.srcDirs
+        classifier = 'sources'
+    }
+
+    artifacts {
+        archives sourcesJar
+    }
+
+} else {
+
+    apply plugin: 'java'
+    apply plugin: 'maven-publish'
+
+    sourceCompatibility = JavaVersion.VERSION_1_8
+    targetCompatibility = JavaVersion.VERSION_1_8
+
+    publishing {
+        publications {
+            maven(MavenPublication) {
+               artifactId = 'echo-api-apache-httpclient'
+
+               from components.java
+            }
+        }
+    }
+
+    task execute(type:JavaExec) {
+       main = System.getProperty('mainClass')
+       classpath = sourceSets.main.runtimeClasspath
+    }
+
+    task sourcesJar(type: Jar, dependsOn: classes) {
+        classifier = 'sources'
+        from sourceSets.main.allSource
+    }
+
+    task javadocJar(type: Jar, dependsOn: javadoc) {
+        classifier = 'javadoc'
+        from javadoc.destinationDir
+    }
+
+    artifacts {
+        archives sourcesJar
+        archives javadocJar
+    }
+}
+
+ext {
+    swagger_annotations_version = "1.6.6"
+    jackson_version = "2.14.1"
+    jackson_databind_version = "2.14.1"
+    jackson_databind_nullable_version = "0.2.4"
+    jakarta_annotation_version = "1.3.5"
+    httpclient_version = "4.5.13"
+    jodatime_version = "2.9.9"
+    junit_version = "4.13.2"
+}
+
+dependencies {
+    implementation "io.swagger:swagger-annotations:$swagger_annotations_version"
+    implementation "com.google.code.findbugs:jsr305:3.0.2"
+    implementation "org.apache.httpcomponents:httpclient:$httpclient_version"
+    implementation "org.apache.httpcomponents:httpmime:$httpclient_version"
+    implementation "com.fasterxml.jackson.core:jackson-core:$jackson_version"
+    implementation "com.fasterxml.jackson.core:jackson-annotations:$jackson_version"
+    implementation "com.fasterxml.jackson.core:jackson-databind:$jackson_databind_version"
+    implementation "com.fasterxml.jackson.jaxrs:jackson-jaxrs-json-provider:$jackson_version"
+    implementation "org.openapitools:jackson-databind-nullable:$jackson_databind_nullable_version"
+    implementation "com.fasterxml.jackson.datatype:jackson-datatype-jsr310:$jackson_version"
+    implementation "jakarta.annotation:jakarta.annotation-api:$jakarta_annotation_version"
+    testImplementation "junit:junit:$junit_version"
+}

samples/client/echo_api/java/apache-httpclient/build.sbt

@@ -0,0 +1 @@
+# TODO

samples/client/echo_api/java/apache-httpclient/docs/Category.md

@@ -0,0 +1,14 @@
+
+
+# Category
+
+
+## Properties
+
+| Name | Type | Description | Notes |
+|------------ | ------------- | ------------- | -------------|
+|**id** | **Long** |  |  [optional] |
+|**name** | **String** |  |  [optional] |
+
+
+

samples/client/echo_api/java/apache-httpclient/docs/PathApi.md

@@ -0,0 +1,77 @@
+# PathApi
+
+All URIs are relative to *http://localhost:3000*
+
+| Method | HTTP request | Description |
+|------------- | ------------- | -------------|
+| [**testsPathStringPathStringIntegerPathInteger**](PathApi.md#testsPathStringPathStringIntegerPathInteger) | **GET** /path/string/{path_string}/integer/{path_integer} | Test path parameter(s) |
+
+
+
+## testsPathStringPathStringIntegerPathInteger
+
+> String testsPathStringPathStringIntegerPathInteger(pathString, pathInteger)
+
+Test path parameter(s)
+
+Test path parameter(s)
+
+### 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.PathApi;
+
+public class Example {
+    public static void main(String[] args) {
+        ApiClient defaultClient = Configuration.getDefaultApiClient();
+        defaultClient.setBasePath("http://localhost:3000");
+
+        PathApi apiInstance = new PathApi(defaultClient);
+        String pathString = "pathString_example"; // String | 
+        Integer pathInteger = 56; // Integer | 
+        try {
+            String result = apiInstance.testsPathStringPathStringIntegerPathInteger(pathString, pathInteger);
+            System.out.println(result);
+        } catch (ApiException e) {
+            System.err.println("Exception when calling PathApi#testsPathStringPathStringIntegerPathInteger");
+            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 |
+|------------- | ------------- | ------------- | -------------|
+| **pathString** | **String**|  | |
+| **pathInteger** | **Integer**|  | |
+
+### Return type
+
+**String**
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+- **Content-Type**: Not defined
+- **Accept**: text/plain
+
+
+### HTTP response details
+| Status code | Description | Response headers |
+|-------------|-------------|------------------|
+| **200** | Successful operation |  -  |
+

samples/client/echo_api/java/apache-httpclient/docs/Pet.md

@@ -0,0 +1,28 @@
+
+
+# Pet
+
+
+## Properties
+
+| Name | Type | Description | Notes |
+|------------ | ------------- | ------------- | -------------|
+|**id** | **Long** |  |  [optional] |
+|**name** | **String** |  |  |
+|**category** | [**Category**](Category.md) |  |  [optional] |
+|**photoUrls** | **List<String>** |  |  |
+|**tags** | [**List<Tag>**](Tag.md) |  |  [optional] |
+|**status** | [**StatusEnum**](#StatusEnum) | pet status in the store |  [optional] |
+
+
+
+## Enum: StatusEnum
+
+| Name | Value |
+|---- | -----|
+| AVAILABLE | "available" |
+| PENDING | "pending" |
+| SOLD | "sold" |
+
+
+

samples/client/echo_api/java/apache-httpclient/docs/QueryApi.md

@@ -0,0 +1,213 @@
+# QueryApi
+
+All URIs are relative to *http://localhost:3000*
+
+| Method | HTTP request | Description |
+|------------- | ------------- | -------------|
+| [**testQueryIntegerBooleanString**](QueryApi.md#testQueryIntegerBooleanString) | **GET** /query/integer/boolean/string | Test query parameter(s) |
+| [**testQueryStyleFormExplodeTrueArrayString**](QueryApi.md#testQueryStyleFormExplodeTrueArrayString) | **GET** /query/style_form/explode_true/array_string | Test query parameter(s) |
+| [**testQueryStyleFormExplodeTrueObject**](QueryApi.md#testQueryStyleFormExplodeTrueObject) | **GET** /query/style_form/explode_true/object | Test query parameter(s) |
+
+
+
+## testQueryIntegerBooleanString
+
+> String testQueryIntegerBooleanString(integerQuery, booleanQuery, stringQuery)
+
+Test query parameter(s)
+
+Test query parameter(s)
+
+### 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.QueryApi;
+
+public class Example {
+    public static void main(String[] args) {
+        ApiClient defaultClient = Configuration.getDefaultApiClient();
+        defaultClient.setBasePath("http://localhost:3000");
+
+        QueryApi apiInstance = new QueryApi(defaultClient);
+        Integer integerQuery = 56; // Integer | 
+        Boolean booleanQuery = true; // Boolean | 
+        String stringQuery = "stringQuery_example"; // String | 
+        try {
+            String result = apiInstance.testQueryIntegerBooleanString(integerQuery, booleanQuery, stringQuery);
+            System.out.println(result);
+        } catch (ApiException e) {
+            System.err.println("Exception when calling QueryApi#testQueryIntegerBooleanString");
+            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 |
+|------------- | ------------- | ------------- | -------------|
+| **integerQuery** | **Integer**|  | [optional] |
+| **booleanQuery** | **Boolean**|  | [optional] |
+| **stringQuery** | **String**|  | [optional] |
+
+### Return type
+
+**String**
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+- **Content-Type**: Not defined
+- **Accept**: text/plain
+
+
+### HTTP response details
+| Status code | Description | Response headers |
+|-------------|-------------|------------------|
+| **200** | Successful operation |  -  |
+
+
+## testQueryStyleFormExplodeTrueArrayString
+
+> String testQueryStyleFormExplodeTrueArrayString(queryObject)
+
+Test query parameter(s)
+
+Test query parameter(s)
+
+### 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.QueryApi;
+
+public class Example {
+    public static void main(String[] args) {
+        ApiClient defaultClient = Configuration.getDefaultApiClient();
+        defaultClient.setBasePath("http://localhost:3000");
+
+        QueryApi apiInstance = new QueryApi(defaultClient);
+        TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter queryObject = new HashMap(); // TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter | 
+        try {
+            String result = apiInstance.testQueryStyleFormExplodeTrueArrayString(queryObject);
+            System.out.println(result);
+        } catch (ApiException e) {
+            System.err.println("Exception when calling QueryApi#testQueryStyleFormExplodeTrueArrayString");
+            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 |
+|------------- | ------------- | ------------- | -------------|
+| **queryObject** | [**TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter**](.md)|  | [optional] |
+
+### Return type
+
+**String**
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+- **Content-Type**: Not defined
+- **Accept**: text/plain
+
+
+### HTTP response details
+| Status code | Description | Response headers |
+|-------------|-------------|------------------|
+| **200** | Successful operation |  -  |
+
+
+## testQueryStyleFormExplodeTrueObject
+
+> String testQueryStyleFormExplodeTrueObject(queryObject)
+
+Test query parameter(s)
+
+Test query parameter(s)
+
+### 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.QueryApi;
+
+public class Example {
+    public static void main(String[] args) {
+        ApiClient defaultClient = Configuration.getDefaultApiClient();
+        defaultClient.setBasePath("http://localhost:3000");
+
+        QueryApi apiInstance = new QueryApi(defaultClient);
+        Pet queryObject = new HashMap(); // Pet | 
+        try {
+            String result = apiInstance.testQueryStyleFormExplodeTrueObject(queryObject);
+            System.out.println(result);
+        } catch (ApiException e) {
+            System.err.println("Exception when calling QueryApi#testQueryStyleFormExplodeTrueObject");
+            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 |
+|------------- | ------------- | ------------- | -------------|
+| **queryObject** | [**Pet**](.md)|  | [optional] |
+
+### Return type
+
+**String**
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+- **Content-Type**: Not defined
+- **Accept**: text/plain
+
+
+### HTTP response details
+| Status code | Description | Response headers |
+|-------------|-------------|------------------|
+| **200** | Successful operation |  -  |
+

samples/client/echo_api/java/apache-httpclient/docs/Tag.md

@@ -0,0 +1,14 @@
+
+
+# Tag
+
+
+## Properties
+
+| Name | Type | Description | Notes |
+|------------ | ------------- | ------------- | -------------|
+|**id** | **Long** |  |  [optional] |
+|**name** | **String** |  |  [optional] |
+
+
+

samples/client/echo_api/java/apache-httpclient/docs/TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter.md

@@ -0,0 +1,13 @@
+
+
+# TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter
+
+
+## Properties
+
+| Name | Type | Description | Notes |
+|------------ | ------------- | ------------- | -------------|
+|**values** | **List<String>** |  |  [optional] |
+
+
+

samples/client/echo_api/java/apache-httpclient/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'

samples/client/echo_api/java/apache-httpclient/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

samples/client/echo_api/java/apache-httpclient/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.2-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

samples/client/echo_api/java/apache-httpclient/gradlew

@@ -0,0 +1,234 @@
+#!/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/master/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
+
+APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
+
+APP_NAME="Gradle"
+APP_BASE_NAME=${0##*/}
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='-Dfile.encoding=UTF-8 "-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&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: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        ulimit -n "$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
+
+# Collect all arguments for the java command;
+#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
+#     shell script including quotes and variable substitutions, so put them in
+#     double quotes to make sure that they get re-expanded; and
+#   * put everything else in single quotes, so that it's not re-expanded.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# 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 "$JAVACMD" "$@"

samples/client/echo_api/java/apache-httpclient/gradlew.bat

@@ -0,0 +1,89 @@
+@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=.
+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=-Dfile.encoding=UTF-8 "-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%" == "0" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+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%"=="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!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

samples/client/echo_api/java/apache-httpclient/pom.xml

@@ -0,0 +1,285 @@
+<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>echo-api-apache-httpclient</artifactId>
+    <packaging>jar</packaging>
+    <name>echo-api-apache-httpclient</name>
+    <version>0.1.0</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>http://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>3.10.1</version>
+                <configuration>
+                    <source>1.8</source>
+                    <target>1.8</target>
+                    <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>3.1.0</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>3.0.0-M7</version>
+                <configuration>
+                    <systemProperties>
+                        <property>
+                            <name>loggerPath</name>
+                            <value>conf/log4j.properties</value>
+                        </property>
+                    </systemProperties>
+                    <argLine>-Xms512m -Xmx1500m</argLine>
+                    <parallel>methods</parallel>
+                    <threadCount>10</threadCount>
+                    <forkMode>pertest</forkMode>
+                </configuration>
+            </plugin>
+            <plugin>
+                <artifactId>maven-dependency-plugin</artifactId>
+                <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>3.3.0</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>3.4.1</version>
+                <configuration>
+                    <doclint>none</doclint>
+                    <source>1.8</source>
+                </configuration>
+                <executions>
+                    <execution>
+                        <id>attach-javadocs</id>
+                        <goals>
+                            <goal>jar</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-source-plugin</artifactId>
+                <version>3.2.1</version>
+                <executions>
+                    <execution>
+                        <id>attach-sources</id>
+                        <goals>
+                            <goal>jar-no-fork</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
+    <profiles>
+        <profile>
+            <id>sign-artifacts</id>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-gpg-plugin</artifactId>
+                        <version>3.0.1</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>
+
+
+        <!-- HTTP client: apache client -->
+        <dependency>
+            <groupId>org.apache.httpcomponents</groupId>
+            <artifactId>httpclient</artifactId>
+            <version>${httpclient-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.httpcomponents</groupId>
+            <artifactId>httpmime</artifactId>
+            <version>${httpclient-version}</version>
+        </dependency>
+
+        <!-- JSON processing: jackson -->
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-core</artifactId>
+            <version>${jackson-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-annotations</artifactId>
+            <version>${jackson-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+            <version>${jackson-databind-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.jaxrs</groupId>
+            <artifactId>jackson-jaxrs-json-provider</artifactId>
+            <version>${jackson-version}</version>
+        </dependency>
+            <dependency>
+                <groupId>com.fasterxml.jackson.datatype</groupId>
+                <artifactId>jackson-datatype-jsr310</artifactId>
+                <version>${jackson-version}</version>
+            </dependency>
+        <dependency>
+            <groupId>org.openapitools</groupId>
+            <artifactId>jackson-databind-nullable</artifactId>
+            <version>${jackson-databind-nullable-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>jakarta.annotation</groupId>
+            <artifactId>jakarta.annotation-api</artifactId>
+            <version>${jakarta-annotation-version}</version>
+            <scope>provided</scope>
+        </dependency>
+        <!-- test dependencies -->
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>${junit-version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <httpclient-version>4.5.13</httpclient-version>
+        <jackson-version>2.14.1</jackson-version>
+        <jackson-databind-version>2.14.1</jackson-databind-version>
+        <jackson-databind-nullable-version>0.2.4</jackson-databind-nullable-version>
+        <jakarta-annotation-version>1.3.5</jakarta-annotation-version>
+        <junit-version>4.13.2</junit-version>
+    </properties>
+</project>

samples/client/echo_api/java/apache-httpclient/settings.gradle

@@ -0,0 +1 @@
+rootProject.name = "echo-api-apache-httpclient"

samples/client/echo_api/java/apache-httpclient/src/main/AndroidManifest.xml

@@ -0,0 +1,3 @@
+<manifest package="org.openapitools.client" xmlns:android="http://schemas.android.com/apk/res/android">
+    <application />
+</manifest>

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/ApiClient.java

@@ -0,0 +1,959 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+package org.openapitools.client;
+
+import com.fasterxml.jackson.annotation.*;
+import com.fasterxml.jackson.databind.*;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+import java.time.OffsetDateTime;
+import com.fasterxml.jackson.jaxrs.json.JacksonJsonProvider;
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JavaType;
+
+import org.apache.http.Header;
+import org.apache.http.HttpEntity;
+import org.apache.http.HttpResponse;
+import org.apache.http.HttpStatus;
+import org.apache.http.NameValuePair;
+import org.apache.http.ParseException;
+import org.apache.http.client.config.RequestConfig;
+import org.apache.http.client.entity.UrlEncodedFormEntity;
+import org.apache.http.client.methods.CloseableHttpResponse;
+import org.apache.http.client.methods.RequestBuilder;
+import org.apache.http.client.protocol.HttpClientContext;
+import org.apache.http.entity.ByteArrayEntity;
+import org.apache.http.entity.ContentType;
+import org.apache.http.entity.FileEntity;
+import org.apache.http.entity.StringEntity;
+import org.apache.http.entity.mime.MultipartEntityBuilder;
+import org.apache.http.impl.client.BasicCookieStore;
+import org.apache.http.impl.client.CloseableHttpClient;
+import org.apache.http.impl.client.HttpClients;
+import org.apache.http.impl.cookie.BasicClientCookie;
+import org.apache.http.message.BasicNameValuePair;
+import org.apache.http.util.EntityUtils;
+import org.apache.http.cookie.Cookie;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Arrays;
+import java.util.ArrayList;
+import java.util.Date;
+import java.util.TimeZone;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import java.net.URLEncoder;
+
+import java.io.File;
+import java.io.InputStream;
+import java.io.IOException;
+import java.io.UnsupportedEncodingException;
+import java.nio.charset.Charset;
+import java.nio.file.Files;
+import java.nio.file.StandardCopyOption;
+import java.nio.file.Paths;
+import java.lang.reflect.Type;
+import java.net.URI;
+
+import java.text.DateFormat;
+
+import org.openapitools.client.auth.Authentication;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class ApiClient extends JavaTimeFormatter {
+  private Map<String, String> defaultHeaderMap = new HashMap<String, String>();
+  private Map<String, String> defaultCookieMap = new HashMap<String, String>();
+  private String basePath = "http://localhost:3000";
+  protected List<ServerConfiguration> servers = new ArrayList<ServerConfiguration>(Arrays.asList(
+    new ServerConfiguration(
+      "http://localhost:3000",
+      "No description provided",
+      new HashMap<String, ServerVariable>()
+    )
+  ));
+  protected Integer serverIndex = 0;
+  protected Map<String, String> serverVariables = null;
+  private boolean debugging = false;
+  private int connectionTimeout = 0;
+
+  private CloseableHttpClient httpClient;
+  private ObjectMapper objectMapper;
+  protected String tempFolderPath = null;
+
+  private Map<String, Authentication> authentications;
+
+  private int statusCode;
+  private Map<String, List<String>> responseHeaders;
+
+  private DateFormat dateFormat;
+
+  // Methods that can have a request body
+  private static List<String> bodyMethods = Arrays.asList("POST", "PUT", "DELETE", "PATCH");
+
+  public ApiClient(CloseableHttpClient httpClient) {
+    objectMapper = new ObjectMapper();
+    objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
+    objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
+    objectMapper.configure(DeserializationFeature.FAIL_ON_INVALID_SUBTYPE, false);
+    objectMapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
+    objectMapper.enable(SerializationFeature.WRITE_ENUMS_USING_TO_STRING);
+    objectMapper.enable(DeserializationFeature.READ_ENUMS_USING_TO_STRING);
+    objectMapper.registerModule(new JavaTimeModule());
+    objectMapper.setDateFormat(ApiClient.buildDefaultDateFormat());
+
+    dateFormat = ApiClient.buildDefaultDateFormat();
+
+    // Set default User-Agent.
+    setUserAgent("OpenAPI-Generator/0.1.0/java");
+
+    // Setup authentications (key: authentication name, value: authentication).
+    authentications = new HashMap<String, Authentication>();
+    // Prevent the authentications from being modified.
+    authentications = Collections.unmodifiableMap(authentications);
+
+    this.httpClient = httpClient;
+  }
+
+  public ApiClient() {
+    this(HttpClients.createDefault());
+  }
+
+  public static DateFormat buildDefaultDateFormat() {
+    return new RFC3339DateFormat();
+  }
+
+  /**
+   * Returns the current object mapper used for JSON serialization/deserialization.
+   * <p>
+   * Note: If you make changes to the object mapper, remember to set it back via
+   * <code>setObjectMapper</code> in order to trigger HTTP client rebuilding.
+   * </p>
+   * @return Object mapper
+   */
+  public ObjectMapper getObjectMapper() {
+    return objectMapper;
+  }
+
+  /**
+   * Sets the object mapper.
+   *
+   * @param objectMapper object mapper
+   * @return API client
+   */
+  public ApiClient setObjectMapper(ObjectMapper objectMapper) {
+    this.objectMapper = objectMapper;
+    return this;
+  }
+
+  public CloseableHttpClient getHttpClient() {
+    return httpClient;
+  }
+
+  /**
+   * Sets the HTTP client.
+   *
+   * @param httpClient HTTP client
+   * @return API client
+   */
+  public ApiClient setHttpClient(CloseableHttpClient httpClient) {
+    this.httpClient = httpClient;
+    return this;
+  }
+
+  public String getBasePath() {
+    return basePath;
+  }
+
+  /**
+   * Sets the base path.
+   *
+   * @param basePath base path
+   * @return API client
+   */
+  public ApiClient setBasePath(String basePath) {
+    this.basePath = basePath;
+    this.serverIndex = null;
+    return this;
+  }
+
+  public List<ServerConfiguration> getServers() {
+    return servers;
+  }
+
+  /**
+   * Sets the server.
+   *
+   * @param servers a list of server configuration
+   * @return API client
+   */
+  public ApiClient setServers(List<ServerConfiguration> servers) {
+    this.servers = servers;
+    return this;
+  }
+
+  public Integer getServerIndex() {
+    return serverIndex;
+  }
+
+  /**
+   * Sets the server index.
+   *
+   * @param serverIndex server index
+   * @return API client
+   */
+  public ApiClient setServerIndex(Integer serverIndex) {
+    this.serverIndex = serverIndex;
+    return this;
+  }
+
+  public Map<String, String> getServerVariables() {
+    return serverVariables;
+  }
+
+  /**
+   * Sets the server variables.
+   *
+   * @param serverVariables server variables
+   * @return API client
+   */
+  public ApiClient setServerVariables(Map<String, String> serverVariables) {
+    this.serverVariables = serverVariables;
+    return this;
+  }
+
+  /**
+   * Gets the status code of the previous request
+   *
+   * @return Status code
+   */
+  public int getStatusCode() {
+    return statusCode;
+  }
+
+  /**
+   * Gets the response headers of the previous request
+   * @return Response headers
+   */
+  public Map<String, List<String>> getResponseHeaders() {
+    return responseHeaders;
+  }
+
+  /**
+   * Get authentications (key: authentication name, value: authentication).
+   * @return Map of authentication
+   */
+  public Map<String, Authentication> getAuthentications() {
+    return authentications;
+  }
+
+  /**
+   * Get authentication for the given name.
+   *
+   * @param authName The authentication name
+   * @return The authentication, null if not found
+   */
+  public Authentication getAuthentication(String authName) {
+    return authentications.get(authName);
+  }
+
+  /**
+   * The path of temporary folder used to store downloaded files from endpoints
+   * with file response. The default value is <code>null</code>, i.e. using
+   * the system's default temporary folder.
+   *
+   * @return Temp folder path
+   */
+  public String getTempFolderPath() {
+    return tempFolderPath;
+  }
+
+
+
+
+
+  /**
+   * Set the User-Agent header's value (by adding to the default header map).
+   * @param userAgent User agent
+   * @return API client
+   */
+  public ApiClient setUserAgent(String userAgent) {
+    addDefaultHeader("User-Agent", userAgent);
+    return this;
+  }
+
+  /**
+   * Set temp folder path
+   * @param tempFolderPath Temp folder path
+   * @return API client
+   */
+  public ApiClient setTempFolderPath(String tempFolderPath) {
+    this.tempFolderPath = tempFolderPath;
+    return this;
+  }
+
+  /**
+   * Add a default header.
+   *
+   * @param key The header's key
+   * @param value The header's value
+   * @return API client
+   */
+  public ApiClient addDefaultHeader(String key, String value) {
+    defaultHeaderMap.put(key, value);
+    return this;
+  }
+
+  /**
+   * Add a default cookie.
+   *
+   * @param key The cookie's key
+   * @param value The cookie's value
+   * @return API client
+   */
+  public ApiClient addDefaultCookie(String key, String value) {
+    defaultCookieMap.put(key, value);
+    return this;
+  }
+
+  /**
+   * Check that whether debugging is enabled for this API client.
+   * @return True if debugging is on
+   */
+  public boolean isDebugging() {
+    return debugging;
+  }
+
+  /**
+   * Enable/disable debugging for this API client.
+   *
+   * @param debugging To enable (true) or disable (false) debugging
+   * @return API client
+   */
+  public ApiClient setDebugging(boolean debugging) {
+    // TODO: implement debugging mode
+    this.debugging = debugging;
+    return this;
+  }
+
+  /**
+   * Connect timeout (in milliseconds).
+   * @return Connection timeout
+   */
+  public int getConnectTimeout() {
+    return connectionTimeout;
+  }
+
+  /**
+   * Set the connect timeout (in milliseconds).
+   * A value of 0 means no timeout, otherwise values must be between 1 and
+   * {@link Integer#MAX_VALUE}.
+   * @param connectionTimeout Connection timeout in milliseconds
+   * @return API client
+   */
+   public ApiClient setConnectTimeout(int connectionTimeout) {
+     this.connectionTimeout = connectionTimeout;
+     return this;
+   }
+
+  /**
+   * Get the date format used to parse/format date parameters.
+   * @return Date format
+   */
+  public DateFormat getDateFormat() {
+    return dateFormat;
+  }
+
+  /**
+   * Set the date format used to parse/format date parameters.
+   * @param dateFormat Date format
+   * @return API client
+   */
+  public ApiClient setDateFormat(DateFormat dateFormat) {
+    this.dateFormat = dateFormat;
+    // Also set the date format for model (de)serialization with Date properties.
+    this.objectMapper.setDateFormat((DateFormat) dateFormat.clone());
+    return this;
+  }
+
+  /**
+   * Parse the given string into Date object.
+   * @param str String
+   * @return Date
+   */
+  public Date parseDate(String str) {
+    try {
+      return dateFormat.parse(str);
+    } catch (java.text.ParseException e) {
+      throw new RuntimeException(e);
+    }
+  }
+
+  /**
+   * Format the given Date object into string.
+   * @param date Date
+   * @return Date in string format
+   */
+  public String formatDate(Date date) {
+    return dateFormat.format(date);
+  }
+
+  /**
+   * Format the given parameter object into string.
+   * @param param Object
+   * @return Object in string format
+   */
+  public String parameterToString(Object param) {
+    if (param == null) {
+      return "";
+    } else if (param instanceof Date) {
+      return formatDate((Date) param);
+    } else if (param instanceof OffsetDateTime) {
+      return formatOffsetDateTime((OffsetDateTime) param);
+    } else if (param instanceof Collection) {
+      StringBuilder b = new StringBuilder();
+      for(Object o : (Collection<?>)param) {
+        if(b.length() > 0) {
+          b.append(',');
+        }
+        b.append(String.valueOf(o));
+      }
+      return b.toString();
+    } else {
+      return String.valueOf(param);
+    }
+  }
+
+  /**
+   * Formats the specified query parameter to a list containing a single {@code Pair} object.
+   *
+   * Note that {@code value} must not be a collection.
+   *
+   * @param name The name of the parameter.
+   * @param value The value of the parameter.
+   * @return A list containing a single {@code Pair} object.
+   */
+  public List<Pair> parameterToPair(String name, Object value) {
+    List<Pair> params = new ArrayList<Pair>();
+
+    // preconditions
+    if (name == null || name.isEmpty() || value == null || value instanceof Collection) {
+      return params;
+    }
+
+    params.add(new Pair(name, escapeString(parameterToString(value))));
+    return params;
+  }
+
+  /**
+   * Formats the specified collection query parameters to a list of {@code Pair} objects.
+   *
+   * Note that the values of each of the returned Pair objects are percent-encoded.
+   *
+   * @param collectionFormat The collection format of the parameter.
+   * @param name The name of the parameter.
+   * @param value The value of the parameter.
+   * @return A list of {@code Pair} objects.
+   */
+  public List<Pair> parameterToPairs(String collectionFormat, String name, Collection value) {
+    List<Pair> params = new ArrayList<Pair>();
+
+    // preconditions
+    if (name == null || name.isEmpty() || value == null) {
+      return params;
+    }
+
+    // create the params based on the collection format
+    if ("multi".equals(collectionFormat)) {
+      for (Object item : value) {
+        params.add(new Pair(name, escapeString(parameterToString(item))));
+      }
+      return params;
+    }
+
+    // collectionFormat is assumed to be "csv" by default
+    String delimiter = ",";
+
+    // escape all delimiters except commas, which are URI reserved
+    // characters
+    if ("ssv".equals(collectionFormat)) {
+      delimiter = escapeString(" ");
+    } else if ("tsv".equals(collectionFormat)) {
+      delimiter = escapeString("\t");
+    } else if ("pipes".equals(collectionFormat)) {
+      delimiter = escapeString("|");
+    }
+
+    StringBuilder sb = new StringBuilder() ;
+    for (Object item : value) {
+      sb.append(delimiter);
+      sb.append(escapeString(parameterToString(item)));
+    }
+
+    params.add(new Pair(name, sb.substring(delimiter.length())));
+
+    return params;
+  }
+
+  /**
+   * Check if the given MIME is a JSON MIME.
+   * JSON MIME examples:
+   *   application/json
+   *   application/json; charset=UTF8
+   *   APPLICATION/JSON
+   *   application/vnd.company+json
+   * @param mime MIME
+   * @return True if MIME type is boolean
+   */
+  public boolean isJsonMime(String mime) {
+    String jsonMime = "(?i)^(application/json|[^;/ \t]+/[^;/ \t]+[+]json)[ \t]*(;.*)?$";
+    return mime != null && (mime.matches(jsonMime) || mime.equals("*/*"));
+  }
+
+  /**
+   * Select the Accept header's value from the given accepts array:
+   *   if JSON exists in the given array, use it;
+   *   otherwise use all of them (joining into a string)
+   *
+   * @param accepts The accepts array to select from
+   * @return The Accept header to use. If the given array is empty,
+   *   null will be returned (not to set the Accept header explicitly).
+   */
+  public String selectHeaderAccept(String[] accepts) {
+    if (accepts.length == 0) {
+      return null;
+    }
+    for (String accept : accepts) {
+      if (isJsonMime(accept)) {
+        return accept;
+      }
+    }
+    return StringUtil.join(accepts, ",");
+  }
+
+  /**
+   * Select the Content-Type header's value from the given array:
+   *   if JSON exists in the given array, use it;
+   *   otherwise use the first one of the array.
+   *
+   * @param contentTypes The Content-Type array to select from
+   * @return The Content-Type header to use. If the given array is empty,
+   *   or matches "any", JSON will be used.
+   */
+  public String selectHeaderContentType(String[] contentTypes) {
+    if (contentTypes.length == 0 || contentTypes[0].equals("*/*")) {
+      return "application/json";
+    }
+    for (String contentType : contentTypes) {
+      if (isJsonMime(contentType)) {
+        return contentType;
+      }
+    }
+    return contentTypes[0];
+  }
+
+  /**
+   * Escape the given string to be used as URL query value.
+   * @param str String
+   * @return Escaped string
+   */
+  public String escapeString(String str) {
+    try {
+      return URLEncoder.encode(str, "utf8").replaceAll("\\+", "%20");
+    } catch (UnsupportedEncodingException e) {
+      return str;
+    }
+  }
+
+  /**
+   * Transforms response headers into map.
+   *
+   * @param headers HTTP headers
+   * @return a map of string array
+   */
+  protected Map<String, List<String>> transformResponseHeaders(Header[] headers) {
+    Map<String, List<String>> headersMap = new HashMap<>();
+    for (Header header : headers) {
+      List<String> valuesList = headersMap.get(header.getName());
+      if (valuesList != null) {
+        valuesList.add(header.getValue());
+      } else {
+        valuesList = new ArrayList<>();
+        valuesList.add(header.getValue());
+        headersMap.put(header.getName(), valuesList);
+      }
+    }
+    return headersMap;
+  }
+
+  /**
+   * Parse content type object from header value
+   */
+  private ContentType getContentType(String headerValue) throws ApiException {
+    try {
+      return ContentType.parse(headerValue);
+    } catch (ParseException e) {
+      throw new ApiException("Could not parse content type " + headerValue);
+    }
+  }
+
+  /**
+   * Get content type of a response or null if one was not provided
+   */
+  private String getResponseMimeType(HttpResponse response) throws ApiException {
+    Header contentTypeHeader = response.getFirstHeader("Content-Type");
+    if (contentTypeHeader != null) {
+      return getContentType(contentTypeHeader.getValue()).getMimeType();
+    }
+    return null;
+  }
+
+  /**
+   * Serialize the given Java object into string according the given
+   * Content-Type (only JSON is supported for now).
+   * @param obj Object
+   * @param contentType Content type
+   * @param formParams Form parameters
+   * @return Object
+   * @throws ApiException API exception
+   */
+  public HttpEntity serialize(Object obj, Map<String, Object> formParams, ContentType contentType) throws ApiException {
+    String mimeType = contentType.getMimeType();
+    if (isJsonMime(mimeType)) {
+      try {
+        return new StringEntity(objectMapper.writeValueAsString(obj), contentType);
+      } catch (JsonProcessingException e) {
+        throw new ApiException(e);
+      }
+    } else if (mimeType.equals(ContentType.MULTIPART_FORM_DATA.getMimeType())) {
+      MultipartEntityBuilder multiPartBuilder = MultipartEntityBuilder.create();
+      for (Entry<String, Object> paramEntry : formParams.entrySet()) {
+        Object value = paramEntry.getValue();
+        if (value instanceof File) {
+          multiPartBuilder.addBinaryBody(paramEntry.getKey(), (File) value);
+        } else if (value instanceof byte[]) {
+          multiPartBuilder.addBinaryBody(paramEntry.getKey(), (byte[]) value);
+        } else {
+          Charset charset = contentType.getCharset();
+          if (charset != null) {
+            ContentType customContentType = ContentType.create(ContentType.TEXT_PLAIN.getMimeType(), charset);
+            multiPartBuilder.addTextBody(paramEntry.getKey(), parameterToString(paramEntry.getValue()),
+                    customContentType);
+          } else {
+            multiPartBuilder.addTextBody(paramEntry.getKey(), parameterToString(paramEntry.getValue()));
+          }
+        }
+      }
+      return multiPartBuilder.build();
+    } else if (mimeType.equals(ContentType.APPLICATION_FORM_URLENCODED.getMimeType())) {
+      List<NameValuePair> formValues = new ArrayList<>();
+      for (Entry<String, Object> paramEntry : formParams.entrySet()) {
+        formValues.add(new BasicNameValuePair(paramEntry.getKey(), parameterToString(paramEntry.getValue())));
+      }
+      return new UrlEncodedFormEntity(formValues, contentType.getCharset());
+    } else {
+      // Handle files with unknown content type
+      if (obj instanceof File) {
+        return new FileEntity((File) obj, contentType);
+      } else if (obj instanceof byte[]) {
+        return new ByteArrayEntity((byte[]) obj, contentType);
+      }
+      throw new ApiException("Serialization for content type '" + contentType + "' not supported");
+    }
+  }
+
+  /**
+   * Deserialize response body to Java object according to the Content-Type.
+   *
+   * @param <T> Type
+   * @param response Response
+   * @param valueType Return type
+   * @return Deserialized object
+   * @throws ApiException API exception
+   * @throws IOException IO exception
+   */
+  @SuppressWarnings("unchecked")
+  public <T> T deserialize(HttpResponse response, TypeReference<T> valueType) throws ApiException, IOException {
+    if (valueType == null) {
+      return null;
+    }
+    HttpEntity entity = response.getEntity();
+    Type valueRawType = valueType.getType();
+    if (valueRawType.equals(byte[].class)) {
+      return (T) EntityUtils.toByteArray(entity);
+    } else if (valueRawType.equals(File.class)) {
+      return (T) downloadFileFromResponse(response);
+    }
+    String mimeType = getResponseMimeType(response);
+    if (mimeType == null || isJsonMime(mimeType)) {
+      // Assume json if no mime type
+      return objectMapper.readValue(entity.getContent(), valueType);
+    } else if ("text/plain".equalsIgnoreCase(mimeType)) {
+      // convert input stream to string
+      java.util.Scanner s = new java.util.Scanner(entity.getContent()).useDelimiter("\\A");
+      return (T) (s.hasNext() ? s.next() : "");
+    } else {
+      throw new ApiException(
+          "Deserialization for content type '" + mimeType + "' not supported for type '" + valueType + "'",
+          response.getStatusLine().getStatusCode(),
+          responseHeaders,
+          EntityUtils.toString(entity)
+      );
+    }
+  }
+
+  private File downloadFileFromResponse(HttpResponse response) throws IOException {
+    Header contentDispositionHeader = response.getFirstHeader("Content-Disposition");
+    String contentDisposition = contentDispositionHeader == null ? null : contentDispositionHeader.getValue();
+    File file = prepareDownloadFile(contentDisposition);
+    Files.copy(response.getEntity().getContent(), file.toPath(), StandardCopyOption.REPLACE_EXISTING);
+    return file;
+  }
+
+  protected File prepareDownloadFile(String contentDisposition) throws IOException {
+    String filename = null;
+    if (contentDisposition != null && !"".equals(contentDisposition)) {
+      // Get filename from the Content-Disposition header.
+      Pattern pattern = Pattern.compile("filename=['\"]?([^'\"\\s]+)['\"]?");
+      Matcher matcher = pattern.matcher(contentDisposition);
+      if (matcher.find())
+        filename = matcher.group(1);
+    }
+
+    String prefix;
+    String suffix = null;
+    if (filename == null) {
+      prefix = "download-";
+      suffix = "";
+    } else {
+      int pos = filename.lastIndexOf('.');
+      if (pos == -1) {
+        prefix = filename + "-";
+      } else {
+        prefix = filename.substring(0, pos) + "-";
+        suffix = filename.substring(pos);
+      }
+      // Files.createTempFile requires the prefix to be at least three characters long
+      if (prefix.length() < 3)
+        prefix = "download-";
+    }
+
+    if (tempFolderPath == null)
+      return Files.createTempFile(prefix, suffix).toFile();
+    else
+      return Files.createTempFile(Paths.get(tempFolderPath), prefix, suffix).toFile();
+  }
+
+  /**
+   * Build full URL by concatenating base path, the given sub path and query parameters.
+   *
+   * @param path The sub path
+   * @param queryParams The query parameters
+   * @param collectionQueryParams The collection query parameters
+   * @return The full URL
+   */
+  private String buildUrl(String path, List<Pair> queryParams, List<Pair> collectionQueryParams) {
+    String baseURL;
+    if (serverIndex != null) {
+      if (serverIndex < 0 || serverIndex >= servers.size()) {
+        throw new ArrayIndexOutOfBoundsException(String.format(
+          "Invalid index %d when selecting the host settings. Must be less than %d", serverIndex, servers.size()
+        ));
+      }
+      baseURL = servers.get(serverIndex).URL(serverVariables);
+    } else {
+      baseURL = basePath;
+    }
+
+    final StringBuilder url = new StringBuilder();
+    url.append(baseURL).append(path);
+
+    if (queryParams != null && !queryParams.isEmpty()) {
+      // support (constant) query string in `path`, e.g. "/posts?draft=1"
+      String prefix = path.contains("?") ? "&" : "?";
+      for (Pair param : queryParams) {
+        if (param.getValue() != null) {
+          if (prefix != null) {
+            url.append(prefix);
+            prefix = null;
+          } else {
+            url.append("&");
+          }
+          String value = parameterToString(param.getValue());
+          // query parameter value already escaped as part of parameterToPair
+          url.append(escapeString(param.getName())).append("=").append(value);
+        }
+      }
+    }
+
+    if (collectionQueryParams != null && !collectionQueryParams.isEmpty()) {
+      String prefix = url.toString().contains("?") ? "&" : "?";
+      for (Pair param : collectionQueryParams) {
+        if (param.getValue() != null) {
+          if (prefix != null) {
+            url.append(prefix);
+            prefix = null;
+          } else {
+            url.append("&");
+          }
+          String value = parameterToString(param.getValue());
+          // collection query parameter value already escaped as part of parameterToPairs
+          url.append(escapeString(param.getName())).append("=").append(value);
+        }
+      }
+    }
+
+    return url.toString();
+  }
+
+  protected boolean isSuccessfulStatus(int statusCode) {
+    return statusCode >= 200 && statusCode < 300;
+  }
+
+  protected boolean isBodyAllowed(String method) {
+    return bodyMethods.contains(method);
+  }
+
+  protected Cookie buildCookie(String key, String value, URI uri) {
+    BasicClientCookie cookie = new BasicClientCookie(key, value);
+    cookie.setDomain(uri.getHost());
+    cookie.setPath("/");
+    return cookie;
+  }
+
+  protected <T> T processResponse(CloseableHttpResponse response, TypeReference<T> returnType) throws ApiException, IOException {
+    statusCode = response.getStatusLine().getStatusCode();
+    if (statusCode == HttpStatus.SC_NO_CONTENT) {
+      return null;
+    }
+
+    responseHeaders = transformResponseHeaders(response.getAllHeaders());
+    if (isSuccessfulStatus(statusCode)) {
+      return this.deserialize(response, returnType);
+    } else {
+      String message = EntityUtils.toString(response.getEntity());
+      throw new ApiException(message, statusCode, responseHeaders, message);
+    }
+  }
+
+  /**
+   * Invoke API by sending HTTP request with the given options.
+   *
+   * @param <T> Type
+   * @param path The sub-path of the HTTP URL
+   * @param method The request method, one of "GET", "POST", "PUT", and "DELETE"
+   * @param queryParams The query parameters
+   * @param collectionQueryParams The collection query parameters
+   * @param body The request body object - if it is not binary, otherwise null
+   * @param headerParams The header parameters
+   * @param cookieParams The cookie parameters
+   * @param formParams The form parameters
+   * @param accept The request's Accept header
+   * @param contentType The request's Content-Type header
+   * @param authNames The authentications to apply
+   * @param returnType Return type
+   * @return The response body in type of string
+   * @throws ApiException API exception
+   */
+   public <T> T invokeAPI(
+       String path,
+       String method,
+       List<Pair> queryParams,
+       List<Pair> collectionQueryParams,
+       Object body,
+       Map<String, String> headerParams,
+       Map<String, String> cookieParams,
+       Map<String, Object> formParams,
+       String accept,
+       String contentType,
+       String[] authNames,
+       TypeReference<T> returnType) throws ApiException {
+    if (body != null && !formParams.isEmpty()) {
+      throw new ApiException("Cannot have body and form params");
+    }
+
+    updateParamsForAuth(authNames, queryParams, headerParams, cookieParams);
+    final String url = buildUrl(path, queryParams, collectionQueryParams);
+
+    RequestBuilder builder = RequestBuilder.create(method);
+    builder.setUri(url);
+
+    RequestConfig config = RequestConfig.custom()
+      .setConnectionRequestTimeout(connectionTimeout)
+      .build();
+    builder.setConfig(config);
+
+    if (accept != null) {
+      builder.addHeader("Accept", accept);
+    }
+    for (Entry<String, String> keyValue : headerParams.entrySet()) {
+      builder.addHeader(keyValue.getKey(), keyValue.getValue());
+    }
+    for (Map.Entry<String,String> keyValue : defaultHeaderMap.entrySet()) {
+      if (!headerParams.containsKey(keyValue.getKey())) {
+        builder.addHeader(keyValue.getKey(), keyValue.getValue());
+      }
+    }
+
+    BasicCookieStore store = new BasicCookieStore();
+    for (Entry<String, String> keyValue : cookieParams.entrySet()) {
+      store.addCookie(buildCookie(keyValue.getKey(), keyValue.getValue(), builder.getUri()));
+    }
+    for (Entry<String,String> keyValue : defaultCookieMap.entrySet()) {
+      if (!cookieParams.containsKey(keyValue.getKey())) {
+        store.addCookie(buildCookie(keyValue.getKey(), keyValue.getValue(), builder.getUri()));
+      }
+    }
+
+    HttpClientContext context = HttpClientContext.create();
+    context.setCookieStore(store);
+
+    ContentType contentTypeObj = getContentType(contentType);
+    if (body != null || !formParams.isEmpty()) {
+      if (isBodyAllowed(method)) {
+        // Add entity if we have content and a valid method
+        builder.setEntity(serialize(body, formParams, contentTypeObj));
+      } else {
+        throw new ApiException("method " + method + " does not support a request body");
+      }
+    }
+
+    try (CloseableHttpResponse response = httpClient.execute(builder.build(), context)) {
+      return processResponse(response, returnType);
+    } catch (IOException e) {
+      throw new ApiException(e);
+    }
+  }
+
+  /**
+   * Update query and header parameters based on authentication settings.
+   *
+   * @param authNames The authentications to apply
+   * @param queryParams Query parameters
+   * @param headerParams Header parameters
+   * @param cookieParams Cookie parameters
+   */
+  private void updateParamsForAuth(String[] authNames, List<Pair> queryParams, Map<String, String> headerParams, Map<String, String> cookieParams) {
+    for (String authName : authNames) {
+      Authentication auth = authentications.get(authName);
+      if (auth == null) throw new RuntimeException("Authentication undefined: " + authName);
+      auth.applyToParams(queryParams, headerParams, cookieParams);
+    }
+  }
+}

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/ApiException.java

@@ -0,0 +1,100 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client;
+
+import java.util.Map;
+import java.util.List;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class ApiException extends Exception {
+    private int code = 0;
+    private Map<String, List<String>> responseHeaders = null;
+    private String responseBody = null;
+
+    public ApiException() {}
+
+    public ApiException(Throwable throwable) {
+        super(throwable);
+    }
+
+    public ApiException(String message) {
+        super(message);
+    }
+
+    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;
+    }
+
+    public ApiException(String message, int code, Map<String, List<String>> responseHeaders, String responseBody) {
+        this(message, (Throwable) null, code, responseHeaders, responseBody);
+    }
+
+    public ApiException(String message, Throwable throwable, int code, Map<String, List<String>> responseHeaders) {
+        this(message, throwable, code, responseHeaders, null);
+    }
+
+    public ApiException(int code, Map<String, List<String>> responseHeaders, String responseBody) {
+        this("Response Code: " + code + " Response Body: " + responseBody, (Throwable) null, code, responseHeaders, responseBody);
+    }
+
+    public ApiException(int code, String message) {
+        super(message);
+        this.code = code;
+    }
+
+    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;
+    }
+
+    @Override
+    public String toString() {
+        return "ApiException{" +
+                "code=" + code +
+                ", responseHeaders=" + responseHeaders +
+                ", responseBody='" + responseBody + '\'' +
+                '}';
+    }
+}

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/Configuration.java

@@ -0,0 +1,39 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Configuration {
+    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;
+    }
+}

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/JavaTimeFormatter.java

@@ -0,0 +1,64 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+package org.openapitools.client;
+
+import java.time.OffsetDateTime;
+import java.time.format.DateTimeFormatter;
+import java.time.format.DateTimeParseException;
+
+/**
+ * Class that add parsing/formatting support for Java 8+ {@code OffsetDateTime} class.
+ * It's generated for java clients when {@code AbstractJavaCodegen#dateLibrary} specified as {@code java8}.
+ */
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class JavaTimeFormatter {
+
+    private DateTimeFormatter offsetDateTimeFormatter = DateTimeFormatter.ISO_OFFSET_DATE_TIME;
+
+    /**
+     * Get the date format used to parse/format {@code OffsetDateTime} parameters.
+     * @return DateTimeFormatter
+     */
+    public DateTimeFormatter getOffsetDateTimeFormatter() {
+        return offsetDateTimeFormatter;
+    }
+
+    /**
+     * Set the date format used to parse/format {@code OffsetDateTime} parameters.
+     * @param offsetDateTimeFormatter {@code DateTimeFormatter}
+     */
+    public void setOffsetDateTimeFormatter(DateTimeFormatter offsetDateTimeFormatter) {
+        this.offsetDateTimeFormatter = offsetDateTimeFormatter;
+    }
+
+    /**
+     * Parse the given string into {@code OffsetDateTime} object.
+     * @param str String
+     * @return {@code OffsetDateTime}
+     */
+    public OffsetDateTime parseOffsetDateTime(String str) {
+        try {
+            return OffsetDateTime.parse(str, offsetDateTimeFormatter);
+        } catch (DateTimeParseException e) {
+            throw new RuntimeException(e);
+        }
+    }
+    /**
+     * Format the given {@code OffsetDateTime} object into string.
+     * @param offsetDateTime {@code OffsetDateTime}
+     * @return {@code OffsetDateTime} in string format
+     */
+    public String formatOffsetDateTime(OffsetDateTime offsetDateTime) {
+        return offsetDateTimeFormatter.format(offsetDateTime);
+    }
+}

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/Pair.java

@@ -0,0 +1,57 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+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;
+    }
+}

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/RFC3339DateFormat.java

@@ -0,0 +1,57 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+package org.openapitools.client;
+
+import com.fasterxml.jackson.databind.util.StdDateFormat;
+
+import java.text.DateFormat;
+import java.text.FieldPosition;
+import java.text.ParsePosition;
+import java.util.Date;
+import java.text.DecimalFormat;
+import java.util.GregorianCalendar;
+import java.util.TimeZone;
+
+public class RFC3339DateFormat extends DateFormat {
+  private static final long serialVersionUID = 1L;
+  private static final TimeZone TIMEZONE_Z = TimeZone.getTimeZone("UTC");
+
+  private final StdDateFormat fmt = new StdDateFormat()
+          .withTimeZone(TIMEZONE_Z)
+          .withColonInTimeZone(true);
+
+  public RFC3339DateFormat() {
+    this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
+  }
+
+  @Override
+  public Date parse(String source) {
+    return parse(source, new ParsePosition(0));
+  }
+
+  @Override
+  public Date parse(String source, ParsePosition pos) {
+    return fmt.parse(source, pos);
+  }
+
+  @Override
+  public StringBuffer format(Date date, StringBuffer toAppendTo, FieldPosition fieldPosition) {
+    return fmt.format(date, toAppendTo, fieldPosition);
+  }
+
+  @Override
+  public Object clone() {
+    return super.clone();
+  }
+}

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/ServerConfiguration.java

@@ -0,0 +1,58 @@
+package org.openapitools.client;
+
+import java.util.Map;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param URL A URL to the target host.
+     * @param description A description of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new IllegalArgumentException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replace("{" + name + "}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/ServerVariable.java

@@ -0,0 +1,23 @@
+package org.openapitools.client;
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/StringUtil.java

@@ -0,0 +1,83 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client;
+
+import java.util.Collection;
+import java.util.Iterator;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class StringUtil {
+  /**
+   * Check if the given array contains the given value (with case-insensitive comparison).
+   *
+   * @param array The array
+   * @param value The value to search
+   * @return true if the array contains the value
+   */
+  public static boolean containsIgnoreCase(String[] array, String value) {
+    for (String str : array) {
+      if (value == null && str == null) {
+        return true;
+      }
+      if (value != null && value.equalsIgnoreCase(str)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  /**
+   * Join an array of strings with the given separator.
+   * <p>
+   * Note: This might be replaced by utility method from commons-lang or guava someday
+   * if one of those libraries is added as dependency.
+   * </p>
+   *
+   * @param array     The array of strings
+   * @param separator The separator
+   * @return the resulting string
+   */
+  public static String join(String[] array, String separator) {
+    int len = array.length;
+    if (len == 0) {
+      return "";
+    }
+
+    StringBuilder out = new StringBuilder();
+    out.append(array[0]);
+    for (int i = 1; i < len; i++) {
+      out.append(separator).append(array[i]);
+    }
+    return out.toString();
+  }
+
+  /**
+   * Join a list of strings with the given separator.
+   *
+   * @param list      The list of strings
+   * @param separator The separator
+   * @return the resulting string
+   */
+  public static String join(Collection<String> list, String separator) {
+    Iterator<String> iterator = list.iterator();
+    StringBuilder out = new StringBuilder();
+    if (iterator.hasNext()) {
+      out.append(iterator.next());
+    }
+    while (iterator.hasNext()) {
+      out.append(separator).append(iterator.next());
+    }
+    return out.toString();
+  }
+}

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/api/PathApi.java

@@ -0,0 +1,114 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+package org.openapitools.client.api;
+
+import com.fasterxml.jackson.core.type.TypeReference;
+
+import org.openapitools.client.ApiException;
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.Configuration;
+import org.openapitools.client.model.*;
+import org.openapitools.client.Pair;
+
+
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class PathApi {
+  private ApiClient apiClient;
+
+  public PathApi() {
+    this(Configuration.getDefaultApiClient());
+  }
+
+  public PathApi(ApiClient apiClient) {
+    this.apiClient = apiClient;
+  }
+
+  public ApiClient getApiClient() {
+    return apiClient;
+  }
+
+  public void setApiClient(ApiClient apiClient) {
+    this.apiClient = apiClient;
+  }
+
+  /**
+   * Test path parameter(s)
+   * Test path parameter(s)
+   * @param pathString  (required)
+   * @param pathInteger  (required)
+   * @return String
+   * @throws ApiException if fails to make API call
+   */
+  public String testsPathStringPathStringIntegerPathInteger(String pathString, Integer pathInteger) throws ApiException {
+    Object localVarPostBody = null;
+    
+    // verify the required parameter 'pathString' is set
+    if (pathString == null) {
+      throw new ApiException(400, "Missing the required parameter 'pathString' when calling testsPathStringPathStringIntegerPathInteger");
+    }
+    
+    // verify the required parameter 'pathInteger' is set
+    if (pathInteger == null) {
+      throw new ApiException(400, "Missing the required parameter 'pathInteger' when calling testsPathStringPathStringIntegerPathInteger");
+    }
+    
+    // create path and map variables
+    String localVarPath = "/path/string/{path_string}/integer/{path_integer}"
+      .replaceAll("\\{" + "path_string" + "\\}", apiClient.escapeString(pathString.toString()))
+      .replaceAll("\\{" + "path_integer" + "\\}", apiClient.escapeString(pathInteger.toString()));
+
+    // query params
+    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 = {
+      "text/plain"
+    };
+    final String localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
+
+    final String[] localVarContentTypes = {
+      
+    };
+    final String localVarContentType = apiClient.selectHeaderContentType(localVarContentTypes);
+
+    String[] localVarAuthNames = new String[] {  };
+
+    TypeReference<String> localVarReturnType = new TypeReference<String>() {};
+    return apiClient.invokeAPI(
+        localVarPath,
+        "GET",
+        localVarQueryParams,
+        localVarCollectionQueryParams,
+        localVarPostBody,
+        localVarHeaderParams,
+        localVarCookieParams,
+        localVarFormParams,
+        localVarAccept,
+        localVarContentType,
+        localVarAuthNames,
+        localVarReturnType
+    );
+  }
+}

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/api/QueryApi.java

@@ -0,0 +1,217 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+package org.openapitools.client.api;
+
+import com.fasterxml.jackson.core.type.TypeReference;
+
+import org.openapitools.client.ApiException;
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.Configuration;
+import org.openapitools.client.model.*;
+import org.openapitools.client.Pair;
+
+import org.openapitools.client.model.Pet;
+import org.openapitools.client.model.TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter;
+
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class QueryApi {
+  private ApiClient apiClient;
+
+  public QueryApi() {
+    this(Configuration.getDefaultApiClient());
+  }
+
+  public QueryApi(ApiClient apiClient) {
+    this.apiClient = apiClient;
+  }
+
+  public ApiClient getApiClient() {
+    return apiClient;
+  }
+
+  public void setApiClient(ApiClient apiClient) {
+    this.apiClient = apiClient;
+  }
+
+  /**
+   * Test query parameter(s)
+   * Test query parameter(s)
+   * @param integerQuery  (optional)
+   * @param booleanQuery  (optional)
+   * @param stringQuery  (optional)
+   * @return String
+   * @throws ApiException if fails to make API call
+   */
+  public String testQueryIntegerBooleanString(Integer integerQuery, Boolean booleanQuery, String stringQuery) throws ApiException {
+    Object localVarPostBody = null;
+    
+    // create path and map variables
+    String localVarPath = "/query/integer/boolean/string";
+
+    // query params
+    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>();
+
+    localVarQueryParams.addAll(apiClient.parameterToPair("integer_query", integerQuery));
+    localVarQueryParams.addAll(apiClient.parameterToPair("boolean_query", booleanQuery));
+    localVarQueryParams.addAll(apiClient.parameterToPair("string_query", stringQuery));
+    
+    
+    
+    final String[] localVarAccepts = {
+      "text/plain"
+    };
+    final String localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
+
+    final String[] localVarContentTypes = {
+      
+    };
+    final String localVarContentType = apiClient.selectHeaderContentType(localVarContentTypes);
+
+    String[] localVarAuthNames = new String[] {  };
+
+    TypeReference<String> localVarReturnType = new TypeReference<String>() {};
+    return apiClient.invokeAPI(
+        localVarPath,
+        "GET",
+        localVarQueryParams,
+        localVarCollectionQueryParams,
+        localVarPostBody,
+        localVarHeaderParams,
+        localVarCookieParams,
+        localVarFormParams,
+        localVarAccept,
+        localVarContentType,
+        localVarAuthNames,
+        localVarReturnType
+    );
+  }
+  /**
+   * Test query parameter(s)
+   * Test query parameter(s)
+   * @param queryObject  (optional)
+   * @return String
+   * @throws ApiException if fails to make API call
+   */
+  public String testQueryStyleFormExplodeTrueArrayString(TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter queryObject) throws ApiException {
+    Object localVarPostBody = null;
+    
+    // create path and map variables
+    String localVarPath = "/query/style_form/explode_true/array_string";
+
+    // query params
+    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>();
+
+    localVarQueryParams.addAll(apiClient.parameterToPairs("multi", "values", queryObject.getValues()));
+    
+    
+    
+    final String[] localVarAccepts = {
+      "text/plain"
+    };
+    final String localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
+
+    final String[] localVarContentTypes = {
+      
+    };
+    final String localVarContentType = apiClient.selectHeaderContentType(localVarContentTypes);
+
+    String[] localVarAuthNames = new String[] {  };
+
+    TypeReference<String> localVarReturnType = new TypeReference<String>() {};
+    return apiClient.invokeAPI(
+        localVarPath,
+        "GET",
+        localVarQueryParams,
+        localVarCollectionQueryParams,
+        localVarPostBody,
+        localVarHeaderParams,
+        localVarCookieParams,
+        localVarFormParams,
+        localVarAccept,
+        localVarContentType,
+        localVarAuthNames,
+        localVarReturnType
+    );
+  }
+  /**
+   * Test query parameter(s)
+   * Test query parameter(s)
+   * @param queryObject  (optional)
+   * @return String
+   * @throws ApiException if fails to make API call
+   */
+  public String testQueryStyleFormExplodeTrueObject(Pet queryObject) throws ApiException {
+    Object localVarPostBody = null;
+    
+    // create path and map variables
+    String localVarPath = "/query/style_form/explode_true/object";
+
+    // query params
+    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>();
+
+    localVarQueryParams.addAll(apiClient.parameterToPair("id", queryObject.getId()));
+    localVarQueryParams.addAll(apiClient.parameterToPair("name", queryObject.getName()));
+    localVarQueryParams.addAll(apiClient.parameterToPair("category", queryObject.getCategory()));
+    localVarQueryParams.addAll(apiClient.parameterToPairs("multi", "photoUrls", queryObject.getPhotoUrls()));
+    localVarQueryParams.addAll(apiClient.parameterToPairs("multi", "tags", queryObject.getTags()));
+    localVarQueryParams.addAll(apiClient.parameterToPair("status", queryObject.getStatus()));
+    
+    
+    
+    final String[] localVarAccepts = {
+      "text/plain"
+    };
+    final String localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
+
+    final String[] localVarContentTypes = {
+      
+    };
+    final String localVarContentType = apiClient.selectHeaderContentType(localVarContentTypes);
+
+    String[] localVarAuthNames = new String[] {  };
+
+    TypeReference<String> localVarReturnType = new TypeReference<String>() {};
+    return apiClient.invokeAPI(
+        localVarPath,
+        "GET",
+        localVarQueryParams,
+        localVarCollectionQueryParams,
+        localVarPostBody,
+        localVarHeaderParams,
+        localVarCookieParams,
+        localVarFormParams,
+        localVarAccept,
+        localVarContentType,
+        localVarAuthNames,
+        localVarReturnType
+    );
+  }
+}

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/auth/ApiKeyAuth.java

@@ -0,0 +1,77 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.auth;
+
+import org.openapitools.client.Pair;
+
+import java.util.Map;
+import java.util.List;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+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) {
+    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);
+    }
+  }
+}

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/auth/Authentication.java

@@ -0,0 +1,30 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.auth;
+
+import org.openapitools.client.Pair;
+
+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
+     */
+    void applyToParams(List<Pair> queryParams, Map<String, String> headerParams, Map<String, String> cookieParams);
+}

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/auth/HttpBasicAuth.java

@@ -0,0 +1,53 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.auth;
+
+import org.openapitools.client.Pair;
+
+import java.util.Base64;
+import java.nio.charset.StandardCharsets;
+
+import java.util.Map;
+import java.util.List;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+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) {
+    if (username == null && password == null) {
+      return;
+    }
+    String str = (username == null ? "" : username) + ":" + (password == null ? "" : password);
+    headerParams.put("Authorization", "Basic " + Base64.getEncoder().encodeToString(str.getBytes(StandardCharsets.UTF_8)));
+  }
+}

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/auth/HttpBearerAuth.java

@@ -0,0 +1,60 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.auth;
+
+import org.openapitools.client.Pair;
+
+import java.util.Map;
+import java.util.List;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class HttpBearerAuth implements Authentication {
+  private final String scheme;
+  private String bearerToken;
+
+  public HttpBearerAuth(String scheme) {
+    this.scheme = scheme;
+  }
+
+  /**
+   * Gets the token, which together with the scheme, will be sent as the value of the Authorization header.
+   *
+   * @return The bearer token
+   */
+  public String getBearerToken() {
+    return bearerToken;
+  }
+
+  /**
+   * 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.bearerToken = bearerToken;
+  }
+
+  @Override
+  public void applyToParams(List<Pair> queryParams, Map<String, String> headerParams, Map<String, String> cookieParams) {
+    if(bearerToken == null) {
+      return;
+    }
+
+    headerParams.put("Authorization", (scheme != null ? upperCaseBearer(scheme) + " " : "") + bearerToken);
+  }
+
+  private static String upperCaseBearer(String scheme) {
+    return ("bearer".equalsIgnoreCase(scheme)) ? "Bearer" : scheme;
+  }
+}

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/model/Category.java

@@ -0,0 +1,136 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+
+/**
+ * Category
+ */
+@JsonPropertyOrder({
+  Category.JSON_PROPERTY_ID,
+  Category.JSON_PROPERTY_NAME
+})
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Category {
+  public static final String JSON_PROPERTY_ID = "id";
+  private Long id;
+
+  public static final String JSON_PROPERTY_NAME = "name";
+  private String name;
+
+  public Category() {
+  }
+
+  public Category id(Long id) {
+    
+    this.id = id;
+    return this;
+  }
+
+   /**
+   * Get id
+   * @return id
+  **/
+  @javax.annotation.Nullable
+  @JsonProperty(JSON_PROPERTY_ID)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Long getId() {
+    return id;
+  }
+
+
+  @JsonProperty(JSON_PROPERTY_ID)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+  public void setId(Long id) {
+    this.id = id;
+  }
+
+
+  public Category name(String name) {
+    
+    this.name = name;
+    return this;
+  }
+
+   /**
+   * Get name
+   * @return name
+  **/
+  @javax.annotation.Nullable
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getName() {
+    return name;
+  }
+
+
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+  public void setName(String name) {
+    this.name = name;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    Category category = (Category) o;
+    return Objects.equals(this.id, category.id) &&
+        Objects.equals(this.name, category.name);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(id, name);
+  }
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class Category {\n");
+    sb.append("    id: ").append(toIndentedString(id)).append("\n");
+    sb.append("    name: ").append(toIndentedString(name)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/model/Pet.java

@@ -0,0 +1,318 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import java.util.ArrayList;
+import java.util.List;
+import org.openapitools.client.model.Category;
+import org.openapitools.client.model.Tag;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+
+/**
+ * Pet
+ */
+@JsonPropertyOrder({
+  Pet.JSON_PROPERTY_ID,
+  Pet.JSON_PROPERTY_NAME,
+  Pet.JSON_PROPERTY_CATEGORY,
+  Pet.JSON_PROPERTY_PHOTO_URLS,
+  Pet.JSON_PROPERTY_TAGS,
+  Pet.JSON_PROPERTY_STATUS
+})
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Pet {
+  public static final String JSON_PROPERTY_ID = "id";
+  private Long id;
+
+  public static final String JSON_PROPERTY_NAME = "name";
+  private String name;
+
+  public static final String JSON_PROPERTY_CATEGORY = "category";
+  private Category category;
+
+  public static final String JSON_PROPERTY_PHOTO_URLS = "photoUrls";
+  private List<String> photoUrls = new ArrayList<>();
+
+  public static final String JSON_PROPERTY_TAGS = "tags";
+  private List<Tag> tags = null;
+
+  /**
+   * pet status in the store
+   */
+  public enum StatusEnum {
+    AVAILABLE("available"),
+    
+    PENDING("pending"),
+    
+    SOLD("sold");
+
+    private String value;
+
+    StatusEnum(String value) {
+      this.value = value;
+    }
+
+    @JsonValue
+    public String getValue() {
+      return value;
+    }
+
+    @Override
+    public String toString() {
+      return String.valueOf(value);
+    }
+
+    @JsonCreator
+    public static StatusEnum fromValue(String value) {
+      for (StatusEnum b : StatusEnum.values()) {
+        if (b.value.equals(value)) {
+          return b;
+        }
+      }
+      throw new IllegalArgumentException("Unexpected value '" + value + "'");
+    }
+  }
+
+  public static final String JSON_PROPERTY_STATUS = "status";
+  private StatusEnum status;
+
+  public Pet() {
+  }
+
+  public Pet id(Long id) {
+    
+    this.id = id;
+    return this;
+  }
+
+   /**
+   * Get id
+   * @return id
+  **/
+  @javax.annotation.Nullable
+  @JsonProperty(JSON_PROPERTY_ID)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Long getId() {
+    return id;
+  }
+
+
+  @JsonProperty(JSON_PROPERTY_ID)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+  public void setId(Long id) {
+    this.id = id;
+  }
+
+
+  public Pet name(String name) {
+    
+    this.name = name;
+    return this;
+  }
+
+   /**
+   * Get name
+   * @return name
+  **/
+  @javax.annotation.Nonnull
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public String getName() {
+    return name;
+  }
+
+
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+  public void setName(String name) {
+    this.name = name;
+  }
+
+
+  public Pet category(Category category) {
+    
+    this.category = category;
+    return this;
+  }
+
+   /**
+   * Get category
+   * @return category
+  **/
+  @javax.annotation.Nullable
+  @JsonProperty(JSON_PROPERTY_CATEGORY)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Category getCategory() {
+    return category;
+  }
+
+
+  @JsonProperty(JSON_PROPERTY_CATEGORY)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+  public void setCategory(Category category) {
+    this.category = category;
+  }
+
+
+  public Pet photoUrls(List<String> photoUrls) {
+    
+    this.photoUrls = photoUrls;
+    return this;
+  }
+
+  public Pet addPhotoUrlsItem(String photoUrlsItem) {
+    this.photoUrls.add(photoUrlsItem);
+    return this;
+  }
+
+   /**
+   * Get photoUrls
+   * @return photoUrls
+  **/
+  @javax.annotation.Nonnull
+  @JsonProperty(JSON_PROPERTY_PHOTO_URLS)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+
+  public List<String> getPhotoUrls() {
+    return photoUrls;
+  }
+
+
+  @JsonProperty(JSON_PROPERTY_PHOTO_URLS)
+  @JsonInclude(value = JsonInclude.Include.ALWAYS)
+  public void setPhotoUrls(List<String> photoUrls) {
+    this.photoUrls = photoUrls;
+  }
+
+
+  public Pet tags(List<Tag> tags) {
+    
+    this.tags = tags;
+    return this;
+  }
+
+  public Pet addTagsItem(Tag tagsItem) {
+    if (this.tags == null) {
+      this.tags = new ArrayList<>();
+    }
+    this.tags.add(tagsItem);
+    return this;
+  }
+
+   /**
+   * Get tags
+   * @return tags
+  **/
+  @javax.annotation.Nullable
+  @JsonProperty(JSON_PROPERTY_TAGS)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public List<Tag> getTags() {
+    return tags;
+  }
+
+
+  @JsonProperty(JSON_PROPERTY_TAGS)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+  public void setTags(List<Tag> tags) {
+    this.tags = tags;
+  }
+
+
+  public Pet status(StatusEnum status) {
+    
+    this.status = status;
+    return this;
+  }
+
+   /**
+   * pet status in the store
+   * @return status
+  **/
+  @javax.annotation.Nullable
+  @JsonProperty(JSON_PROPERTY_STATUS)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public StatusEnum getStatus() {
+    return status;
+  }
+
+
+  @JsonProperty(JSON_PROPERTY_STATUS)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+  public void setStatus(StatusEnum status) {
+    this.status = status;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    Pet pet = (Pet) o;
+    return Objects.equals(this.id, pet.id) &&
+        Objects.equals(this.name, pet.name) &&
+        Objects.equals(this.category, pet.category) &&
+        Objects.equals(this.photoUrls, pet.photoUrls) &&
+        Objects.equals(this.tags, pet.tags) &&
+        Objects.equals(this.status, pet.status);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(id, name, category, photoUrls, tags, status);
+  }
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class Pet {\n");
+    sb.append("    id: ").append(toIndentedString(id)).append("\n");
+    sb.append("    name: ").append(toIndentedString(name)).append("\n");
+    sb.append("    category: ").append(toIndentedString(category)).append("\n");
+    sb.append("    photoUrls: ").append(toIndentedString(photoUrls)).append("\n");
+    sb.append("    tags: ").append(toIndentedString(tags)).append("\n");
+    sb.append("    status: ").append(toIndentedString(status)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/model/Tag.java

@@ -0,0 +1,136 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+
+/**
+ * Tag
+ */
+@JsonPropertyOrder({
+  Tag.JSON_PROPERTY_ID,
+  Tag.JSON_PROPERTY_NAME
+})
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class Tag {
+  public static final String JSON_PROPERTY_ID = "id";
+  private Long id;
+
+  public static final String JSON_PROPERTY_NAME = "name";
+  private String name;
+
+  public Tag() {
+  }
+
+  public Tag id(Long id) {
+    
+    this.id = id;
+    return this;
+  }
+
+   /**
+   * Get id
+   * @return id
+  **/
+  @javax.annotation.Nullable
+  @JsonProperty(JSON_PROPERTY_ID)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public Long getId() {
+    return id;
+  }
+
+
+  @JsonProperty(JSON_PROPERTY_ID)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+  public void setId(Long id) {
+    this.id = id;
+  }
+
+
+  public Tag name(String name) {
+    
+    this.name = name;
+    return this;
+  }
+
+   /**
+   * Get name
+   * @return name
+  **/
+  @javax.annotation.Nullable
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public String getName() {
+    return name;
+  }
+
+
+  @JsonProperty(JSON_PROPERTY_NAME)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+  public void setName(String name) {
+    this.name = name;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    Tag tag = (Tag) o;
+    return Objects.equals(this.id, tag.id) &&
+        Objects.equals(this.name, tag.name);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(id, name);
+  }
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class Tag {\n");
+    sb.append("    id: ").append(toIndentedString(id)).append("\n");
+    sb.append("    name: ").append(toIndentedString(name)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/model/TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter.java

@@ -0,0 +1,115 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import java.util.Objects;
+import java.util.Arrays;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import java.util.ArrayList;
+import java.util.List;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+
+/**
+ * TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter
+ */
+@JsonPropertyOrder({
+  TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter.JSON_PROPERTY_VALUES
+})
+@JsonTypeName("test_query_style_form_explode_true_array_string_query_object_parameter")
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter {
+  public static final String JSON_PROPERTY_VALUES = "values";
+  private List<String> values = null;
+
+  public TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter() {
+  }
+
+  public TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter values(List<String> values) {
+    
+    this.values = values;
+    return this;
+  }
+
+  public TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter addValuesItem(String valuesItem) {
+    if (this.values == null) {
+      this.values = new ArrayList<>();
+    }
+    this.values.add(valuesItem);
+    return this;
+  }
+
+   /**
+   * Get values
+   * @return values
+  **/
+  @javax.annotation.Nullable
+  @JsonProperty(JSON_PROPERTY_VALUES)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+
+  public List<String> getValues() {
+    return values;
+  }
+
+
+  @JsonProperty(JSON_PROPERTY_VALUES)
+  @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
+  public void setValues(List<String> values) {
+    this.values = values;
+  }
+
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter testQueryStyleFormExplodeTrueArrayStringQueryObjectParameter = (TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter) o;
+    return Objects.equals(this.values, testQueryStyleFormExplodeTrueArrayStringQueryObjectParameter.values);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(values);
+  }
+
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder();
+    sb.append("class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter {\n");
+    sb.append("    values: ").append(toIndentedString(values)).append("\n");
+    sb.append("}");
+    return sb.toString();
+  }
+
+  /**
+   * Convert the given object to string with each line indented by 4 spaces
+   * (except the first line).
+   */
+  private String toIndentedString(Object o) {
+    if (o == null) {
+      return "null";
+    }
+    return o.toString().replace("\n", "\n    ");
+  }
+
+}
+

samples/client/echo_api/java/apache-httpclient/src/test/java/org/openapitools/client/CustomTest.java

@@ -0,0 +1,85 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.oprg
+ *
+ * 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 org.junit.Assert;
+import org.openapitools.client.ApiException;
+import org.openapitools.client.api.QueryApi;
+import org.openapitools.client.model.Category;
+import org.openapitools.client.model.Pet;
+import org.openapitools.client.model.TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter;
+import org.junit.Test;
+import org.junit.Ignore;
+
+import java.util.*;
+
+
+/**
+ * API tests for QueryApi
+ */
+public class CustomTest {
+
+    private final QueryApi api = new QueryApi();
+
+
+    /**
+     * Test query parameter(s)
+     * <p>
+     * Test query parameter(s)
+     *
+     * @throws ApiException if the Api call fails
+     */
+    @Test
+    public void testQueryStyleFormExplodeTrueObjectTest() throws ApiException {
+        Pet queryObject = new Pet().id(12345L).name("Hello World").
+                photoUrls(Arrays.asList(new String[]{"http://a.com", "http://b.com"})).category(new Category().id(987L).name("new category"));
+
+        // TODO uncomment below to test deepObject
+        //String response = api.testQueryStyleFormExplodeTrueObject(queryObject);
+        //org.openapitools.client.EchoServerResponseParser p = new org.openapitools.client.EchoServerResponseParser(response);
+        //Assert.assertEquals("/query/style_form/explode_true/object?id=12345&name=Hello%20World&category=class%20Category%20%7B%0A%20%20%20%20id%3A%20987%0A%20%20%20%20name%3A%20new%20category%0A%7D&photoUrls=http%3A%2F%2Fa.com&photoUrls=http%3A%2F%2Fb.com", p.path);
+    }
+
+    /**
+     * Test query parameter(s)
+     * <p>
+     * Test query parameter(s)
+     *
+     * @throws ApiException if the Api call fails
+     */
+    @Test
+    public void testQueryStyleFormExplodeTrueArrayString() throws ApiException {
+        TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter q = new TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter()
+                .values(Arrays.asList(new String[]{"hello world 1", "hello world 2"}));
+
+        String response = api.testQueryStyleFormExplodeTrueArrayString(q);
+        org.openapitools.client.EchoServerResponseParser p = new org.openapitools.client.EchoServerResponseParser(response);
+        Assert.assertEquals("/query/style_form/explode_true/array_string?values=hello%20world%201&values=hello%20world%202", p.path);
+    }
+
+    /**
+     * Test query parameter(s)
+     * <p>
+     * Test query parameter(s)
+     *
+     * @throws ApiException if the Api call fails
+     */
+    @Test
+    public void testQueryIntegerBooleanString() throws ApiException {
+        String response = api.testQueryIntegerBooleanString(1, true, "Hello World");
+        org.openapitools.client.EchoServerResponseParser p = new org.openapitools.client.EchoServerResponseParser(response);
+        Assert.assertEquals("/query/integer/boolean/string?integer_query=1&boolean_query=true&string_query=Hello%20World", p.path);
+    }
+
+}

samples/client/echo_api/java/apache-httpclient/src/test/java/org/openapitools/client/EchoServerResponseParser.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2018 OpenAPI-Generator Contributors (https://openapi-generator.tech)
+ *
+ * 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.
+ */
+
+package org.openapitools.client;
+
+public class EchoServerResponseParser {
+    public String method; // e.g. GET
+    public String path; // e.g. /query/style_form/explode_true/object?id=12345
+    public String protocol; // e.g. HTTP/1.1
+    public java.util.HashMap<String, String> headers = new java.util.HashMap<>();
+
+    public EchoServerResponseParser(String response) {
+        if (response == null) {
+            throw new RuntimeException("Echo server response cannot be null");
+        }
+
+        String[] lines = response.split("\n");
+        boolean firstLine = true;
+
+        for (String line : lines) {
+            if (firstLine) {
+                String[] items = line.split(" ");
+                this.method = items[0];
+                this.path = items[1];
+                this.protocol = items[2];
+                firstLine = false;
+                continue;
+            }
+
+            // store the header key-value pair in headers
+            String[] keyValue = line.split(": ");
+            if (keyValue.length == 2) { // skip blank line, non key-value pair
+                this.headers.put(keyValue[0], keyValue[1]);
+            }
+        }
+
+    }
+}

samples/client/echo_api/java/apache-httpclient/src/test/java/org/openapitools/client/api/PathApiTest.java

@@ -0,0 +1,52 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiException;
+import org.junit.Test;
+import org.junit.Ignore;
+import org.junit.Assert;
+
+import java.time.LocalDate;
+import java.time.OffsetDateTime;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * API tests for PathApi
+ */
+@Ignore
+public class PathApiTest {
+
+    private final PathApi api = new PathApi();
+
+    /**
+     * Test path parameter(s)
+     *
+     * Test path parameter(s)
+     *
+     * @throws ApiException
+     *          if the Api call fails
+     */
+    @Test
+    public void testsPathStringPathStringIntegerPathIntegerTest() throws ApiException {
+        String pathString = null;
+        Integer pathInteger = null;
+        String response = api.testsPathStringPathStringIntegerPathInteger(pathString, pathInteger);
+
+        // TODO: test validations
+    }
+}

samples/client/echo_api/java/apache-httpclient/src/test/java/org/openapitools/client/api/QueryApiTest.java

@@ -0,0 +1,85 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiException;
+import org.openapitools.client.model.Pet;
+import org.openapitools.client.model.TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter;
+import org.junit.Test;
+import org.junit.Ignore;
+import org.junit.Assert;
+
+import java.time.LocalDate;
+import java.time.OffsetDateTime;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * API tests for QueryApi
+ */
+@Ignore
+public class QueryApiTest {
+
+    private final QueryApi api = new QueryApi();
+
+    /**
+     * Test query parameter(s)
+     *
+     * Test query parameter(s)
+     *
+     * @throws ApiException
+     *          if the Api call fails
+     */
+    @Test
+    public void testQueryIntegerBooleanStringTest() throws ApiException {
+        Integer integerQuery = null;
+        Boolean booleanQuery = null;
+        String stringQuery = null;
+        String response = api.testQueryIntegerBooleanString(integerQuery, booleanQuery, stringQuery);
+
+        // TODO: test validations
+    }
+    /**
+     * Test query parameter(s)
+     *
+     * Test query parameter(s)
+     *
+     * @throws ApiException
+     *          if the Api call fails
+     */
+    @Test
+    public void testQueryStyleFormExplodeTrueArrayStringTest() throws ApiException {
+        TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter queryObject = null;
+        String response = api.testQueryStyleFormExplodeTrueArrayString(queryObject);
+
+        // TODO: test validations
+    }
+    /**
+     * Test query parameter(s)
+     *
+     * Test query parameter(s)
+     *
+     * @throws ApiException
+     *          if the Api call fails
+     */
+    @Test
+    public void testQueryStyleFormExplodeTrueObjectTest() throws ApiException {
+        Pet queryObject = null;
+        String response = api.testQueryStyleFormExplodeTrueObject(queryObject);
+
+        // TODO: test validations
+    }
+}

samples/client/echo_api/java/apache-httpclient/src/test/java/org/openapitools/client/model/CategoryTest.java

@@ -0,0 +1,56 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for Category
+ */
+public class CategoryTest {
+    private final Category model = new Category();
+
+    /**
+     * Model tests for Category
+     */
+    @Test
+    public void testCategory() {
+        // TODO: test Category
+    }
+
+    /**
+     * Test the property 'id'
+     */
+    @Test
+    public void idTest() {
+        // TODO: test id
+    }
+
+    /**
+     * Test the property 'name'
+     */
+    @Test
+    public void nameTest() {
+        // TODO: test name
+    }
+
+}

samples/client/echo_api/java/apache-httpclient/src/test/java/org/openapitools/client/model/PetTest.java

@@ -0,0 +1,92 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import java.util.ArrayList;
+import java.util.List;
+import org.openapitools.client.model.Category;
+import org.openapitools.client.model.Tag;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for Pet
+ */
+public class PetTest {
+    private final Pet model = new Pet();
+
+    /**
+     * Model tests for Pet
+     */
+    @Test
+    public void testPet() {
+        // TODO: test Pet
+    }
+
+    /**
+     * Test the property 'id'
+     */
+    @Test
+    public void idTest() {
+        // TODO: test id
+    }
+
+    /**
+     * Test the property 'name'
+     */
+    @Test
+    public void nameTest() {
+        // TODO: test name
+    }
+
+    /**
+     * Test the property 'category'
+     */
+    @Test
+    public void categoryTest() {
+        // TODO: test category
+    }
+
+    /**
+     * Test the property 'photoUrls'
+     */
+    @Test
+    public void photoUrlsTest() {
+        // TODO: test photoUrls
+    }
+
+    /**
+     * Test the property 'tags'
+     */
+    @Test
+    public void tagsTest() {
+        // TODO: test tags
+    }
+
+    /**
+     * Test the property 'status'
+     */
+    @Test
+    public void statusTest() {
+        // TODO: test status
+    }
+
+}

samples/client/echo_api/java/apache-httpclient/src/test/java/org/openapitools/client/model/TagTest.java

@@ -0,0 +1,56 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for Tag
+ */
+public class TagTest {
+    private final Tag model = new Tag();
+
+    /**
+     * Model tests for Tag
+     */
+    @Test
+    public void testTag() {
+        // TODO: test Tag
+    }
+
+    /**
+     * Test the property 'id'
+     */
+    @Test
+    public void idTest() {
+        // TODO: test id
+    }
+
+    /**
+     * Test the property 'name'
+     */
+    @Test
+    public void nameTest() {
+        // TODO: test name
+    }
+
+}

samples/client/echo_api/java/apache-httpclient/src/test/java/org/openapitools/client/model/TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameterTest.java

@@ -0,0 +1,50 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.model;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.annotation.JsonValue;
+import java.util.ArrayList;
+import java.util.List;
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+
+/**
+ * Model tests for TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter
+ */
+public class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameterTest {
+    private final TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter model = new TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter();
+
+    /**
+     * Model tests for TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter
+     */
+    @Test
+    public void testTestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter() {
+        // TODO: test TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter
+    }
+
+    /**
+     * Test the property 'values'
+     */
+    @Test
+    public void valuesTest() {
+        // TODO: test values
+    }
+
+}

samples/client/echo_api/java/native/.openapi-generator/FILES

@@ -6,6 +6,7 @@ api/openapi.yaml
 build.gradle
 build.sbt
 docs/Category.md
+docs/PathApi.md
 docs/Pet.md
 docs/QueryApi.md
 docs/Tag.md
@@ -28,6 +29,7 @@ src/main/java/org/openapitools/client/Pair.java
 src/main/java/org/openapitools/client/RFC3339DateFormat.java
 src/main/java/org/openapitools/client/ServerConfiguration.java
 src/main/java/org/openapitools/client/ServerVariable.java
+src/main/java/org/openapitools/client/api/PathApi.java
 src/main/java/org/openapitools/client/api/QueryApi.java
 src/main/java/org/openapitools/client/model/AbstractOpenApiSchema.java
 src/main/java/org/openapitools/client/model/Category.java

samples/client/echo_api/java/native/README.md

@@ -74,21 +74,22 @@ Please follow the [installation](#installation) instruction and execute the foll
 
 import org.openapitools.client.*;
 import org.openapitools.client.model.*;
-import org.openapitools.client.api.QueryApi;
+import org.openapitools.client.api.PathApi;
 
-public class QueryApiExample {
+public class PathApiExample {
 
     public static void main(String[] args) {
         ApiClient defaultClient = Configuration.getDefaultApiClient();
         // Configure clients using the `defaultClient` object, such as
         // overriding the host and port, timeout, etc.
-        QueryApi apiInstance = new QueryApi(defaultClient);
+        PathApi apiInstance = new PathApi(defaultClient);
-        TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter queryObject = new HashMap(); // TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter | 
+        String pathString = "pathString_example"; // String | 
+        Integer pathInteger = 56; // Integer | 
         try {
-            String result = apiInstance.testQueryStyleFormExplodeTrueArrayString(queryObject);
+            String result = apiInstance.testsPathStringPathStringIntegerPathInteger(pathString, pathInteger);
             System.out.println(result);
         } catch (ApiException e) {
-            System.err.println("Exception when calling QueryApi#testQueryStyleFormExplodeTrueArrayString");
+            System.err.println("Exception when calling PathApi#testsPathStringPathStringIntegerPathInteger");
             System.err.println("Status code: " + e.getCode());
             System.err.println("Reason: " + e.getResponseBody());
             System.err.println("Response headers: " + e.getResponseHeaders());
@@ -105,6 +106,10 @@ All URIs are relative to *http://localhost:3000*
 
 Class | Method | HTTP request | Description
 ------------ | ------------- | ------------- | -------------
+*PathApi* | [**testsPathStringPathStringIntegerPathInteger**](docs/PathApi.md#testsPathStringPathStringIntegerPathInteger) | **GET** /path/string/{path_string}/integer/{path_integer} | Test path parameter(s)
+*PathApi* | [**testsPathStringPathStringIntegerPathIntegerWithHttpInfo**](docs/PathApi.md#testsPathStringPathStringIntegerPathIntegerWithHttpInfo) | **GET** /path/string/{path_string}/integer/{path_integer} | Test path parameter(s)
+*QueryApi* | [**testQueryIntegerBooleanString**](docs/QueryApi.md#testQueryIntegerBooleanString) | **GET** /query/integer/boolean/string | Test query parameter(s)
+*QueryApi* | [**testQueryIntegerBooleanStringWithHttpInfo**](docs/QueryApi.md#testQueryIntegerBooleanStringWithHttpInfo) | **GET** /query/integer/boolean/string | Test query parameter(s)
 *QueryApi* | [**testQueryStyleFormExplodeTrueArrayString**](docs/QueryApi.md#testQueryStyleFormExplodeTrueArrayString) | **GET** /query/style_form/explode_true/array_string | Test query parameter(s)
 *QueryApi* | [**testQueryStyleFormExplodeTrueArrayStringWithHttpInfo**](docs/QueryApi.md#testQueryStyleFormExplodeTrueArrayStringWithHttpInfo) | **GET** /query/style_form/explode_true/array_string | Test query parameter(s)
 *QueryApi* | [**testQueryStyleFormExplodeTrueObject**](docs/QueryApi.md#testQueryStyleFormExplodeTrueObject) | **GET** /query/style_form/explode_true/object | Test query parameter(s)

samples/client/echo_api/java/native/api/openapi.yaml

@@ -11,6 +11,73 @@ info:
 servers:
 - url: http://localhost:3000/
 paths:
+  /path/string/{path_string}/integer/{path_integer}:
+    get:
+      description: Test path parameter(s)
+      operationId: "tests/path/string/{path_string}/integer/{path_integer}"
+      parameters:
+      - explode: false
+        in: path
+        name: path_string
+        required: true
+        schema:
+          type: string
+        style: simple
+      - explode: false
+        in: path
+        name: path_integer
+        required: true
+        schema:
+          type: integer
+        style: simple
+      responses:
+        "200":
+          content:
+            text/plain:
+              schema:
+                type: string
+          description: Successful operation
+      summary: Test path parameter(s)
+      tags:
+      - path
+      x-accepts: text/plain
+  /query/integer/boolean/string:
+    get:
+      description: Test query parameter(s)
+      operationId: test/query/integer/boolean/string
+      parameters:
+      - explode: true
+        in: query
+        name: integer_query
+        required: false
+        schema:
+          type: integer
+        style: form
+      - explode: true
+        in: query
+        name: boolean_query
+        required: false
+        schema:
+          type: boolean
+        style: form
+      - explode: true
+        in: query
+        name: string_query
+        required: false
+        schema:
+          type: string
+        style: form
+      responses:
+        "200":
+          content:
+            text/plain:
+              schema:
+                type: string
+          description: Successful operation
+      summary: Test query parameter(s)
+      tags:
+      - query
+      x-accepts: text/plain
   /query/style_form/explode_true/array_string:
     get:
       description: Test query parameter(s)

samples/client/echo_api/java/native/docs/PathApi.md

@@ -0,0 +1,148 @@
+# PathApi
+
+All URIs are relative to *http://localhost:3000*
+
+| Method | HTTP request | Description |
+|------------- | ------------- | -------------|
+| [**testsPathStringPathStringIntegerPathInteger**](PathApi.md#testsPathStringPathStringIntegerPathInteger) | **GET** /path/string/{path_string}/integer/{path_integer} | Test path parameter(s) |
+| [**testsPathStringPathStringIntegerPathIntegerWithHttpInfo**](PathApi.md#testsPathStringPathStringIntegerPathIntegerWithHttpInfo) | **GET** /path/string/{path_string}/integer/{path_integer} | Test path parameter(s) |
+
+
+
+## testsPathStringPathStringIntegerPathInteger
+
+> String testsPathStringPathStringIntegerPathInteger(pathString, pathInteger)
+
+Test path parameter(s)
+
+Test path parameter(s)
+
+### 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.PathApi;
+
+public class Example {
+    public static void main(String[] args) {
+        ApiClient defaultClient = Configuration.getDefaultApiClient();
+        defaultClient.setBasePath("http://localhost:3000");
+
+        PathApi apiInstance = new PathApi(defaultClient);
+        String pathString = "pathString_example"; // String | 
+        Integer pathInteger = 56; // Integer | 
+        try {
+            String result = apiInstance.testsPathStringPathStringIntegerPathInteger(pathString, pathInteger);
+            System.out.println(result);
+        } catch (ApiException e) {
+            System.err.println("Exception when calling PathApi#testsPathStringPathStringIntegerPathInteger");
+            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 |
+|------------- | ------------- | ------------- | -------------|
+| **pathString** | **String**|  | |
+| **pathInteger** | **Integer**|  | |
+
+### Return type
+
+**String**
+
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+- **Content-Type**: Not defined
+- **Accept**: text/plain
+
+### HTTP response details
+| Status code | Description | Response headers |
+|-------------|-------------|------------------|
+| **200** | Successful operation |  -  |
+
+## testsPathStringPathStringIntegerPathIntegerWithHttpInfo
+
+> ApiResponse<String> testsPathStringPathStringIntegerPathInteger testsPathStringPathStringIntegerPathIntegerWithHttpInfo(pathString, pathInteger)
+
+Test path parameter(s)
+
+Test path parameter(s)
+
+### Example
+
+```java
+// Import classes:
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.ApiException;
+import org.openapitools.client.ApiResponse;
+import org.openapitools.client.Configuration;
+import org.openapitools.client.models.*;
+import org.openapitools.client.api.PathApi;
+
+public class Example {
+    public static void main(String[] args) {
+        ApiClient defaultClient = Configuration.getDefaultApiClient();
+        defaultClient.setBasePath("http://localhost:3000");
+
+        PathApi apiInstance = new PathApi(defaultClient);
+        String pathString = "pathString_example"; // String | 
+        Integer pathInteger = 56; // Integer | 
+        try {
+            ApiResponse<String> response = apiInstance.testsPathStringPathStringIntegerPathIntegerWithHttpInfo(pathString, pathInteger);
+            System.out.println("Status code: " + response.getStatusCode());
+            System.out.println("Response headers: " + response.getHeaders());
+            System.out.println("Response body: " + response.getData());
+        } catch (ApiException e) {
+            System.err.println("Exception when calling PathApi#testsPathStringPathStringIntegerPathInteger");
+            System.err.println("Status code: " + e.getCode());
+            System.err.println("Response headers: " + e.getResponseHeaders());
+            System.err.println("Reason: " + e.getResponseBody());
+            e.printStackTrace();
+        }
+    }
+}
+```
+
+### Parameters
+
+
+| Name | Type | Description  | Notes |
+|------------- | ------------- | ------------- | -------------|
+| **pathString** | **String**|  | |
+| **pathInteger** | **Integer**|  | |
+
+### Return type
+
+ApiResponse<**String**>
+
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+- **Content-Type**: Not defined
+- **Accept**: text/plain
+
+### HTTP response details
+| Status code | Description | Response headers |
+|-------------|-------------|------------------|
+| **200** | Successful operation |  -  |
+

samples/client/echo_api/java/native/docs/QueryApi.md

@@ -4,6 +4,8 @@ All URIs are relative to *http://localhost:3000*
 
 | Method | HTTP request | Description |
 |------------- | ------------- | -------------|
+| [**testQueryIntegerBooleanString**](QueryApi.md#testQueryIntegerBooleanString) | **GET** /query/integer/boolean/string | Test query parameter(s) |
+| [**testQueryIntegerBooleanStringWithHttpInfo**](QueryApi.md#testQueryIntegerBooleanStringWithHttpInfo) | **GET** /query/integer/boolean/string | Test query parameter(s) |
 | [**testQueryStyleFormExplodeTrueArrayString**](QueryApi.md#testQueryStyleFormExplodeTrueArrayString) | **GET** /query/style_form/explode_true/array_string | Test query parameter(s) |
 | [**testQueryStyleFormExplodeTrueArrayStringWithHttpInfo**](QueryApi.md#testQueryStyleFormExplodeTrueArrayStringWithHttpInfo) | **GET** /query/style_form/explode_true/array_string | Test query parameter(s) |
 | [**testQueryStyleFormExplodeTrueObject**](QueryApi.md#testQueryStyleFormExplodeTrueObject) | **GET** /query/style_form/explode_true/object | Test query parameter(s) |
@@ -11,6 +13,148 @@ All URIs are relative to *http://localhost:3000*
 
 
 
+## testQueryIntegerBooleanString
+
+> String testQueryIntegerBooleanString(integerQuery, booleanQuery, stringQuery)
+
+Test query parameter(s)
+
+Test query parameter(s)
+
+### 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.QueryApi;
+
+public class Example {
+    public static void main(String[] args) {
+        ApiClient defaultClient = Configuration.getDefaultApiClient();
+        defaultClient.setBasePath("http://localhost:3000");
+
+        QueryApi apiInstance = new QueryApi(defaultClient);
+        Integer integerQuery = 56; // Integer | 
+        Boolean booleanQuery = true; // Boolean | 
+        String stringQuery = "stringQuery_example"; // String | 
+        try {
+            String result = apiInstance.testQueryIntegerBooleanString(integerQuery, booleanQuery, stringQuery);
+            System.out.println(result);
+        } catch (ApiException e) {
+            System.err.println("Exception when calling QueryApi#testQueryIntegerBooleanString");
+            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 |
+|------------- | ------------- | ------------- | -------------|
+| **integerQuery** | **Integer**|  | [optional] |
+| **booleanQuery** | **Boolean**|  | [optional] |
+| **stringQuery** | **String**|  | [optional] |
+
+### Return type
+
+**String**
+
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+- **Content-Type**: Not defined
+- **Accept**: text/plain
+
+### HTTP response details
+| Status code | Description | Response headers |
+|-------------|-------------|------------------|
+| **200** | Successful operation |  -  |
+
+## testQueryIntegerBooleanStringWithHttpInfo
+
+> ApiResponse<String> testQueryIntegerBooleanString testQueryIntegerBooleanStringWithHttpInfo(integerQuery, booleanQuery, stringQuery)
+
+Test query parameter(s)
+
+Test query parameter(s)
+
+### Example
+
+```java
+// Import classes:
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.ApiException;
+import org.openapitools.client.ApiResponse;
+import org.openapitools.client.Configuration;
+import org.openapitools.client.models.*;
+import org.openapitools.client.api.QueryApi;
+
+public class Example {
+    public static void main(String[] args) {
+        ApiClient defaultClient = Configuration.getDefaultApiClient();
+        defaultClient.setBasePath("http://localhost:3000");
+
+        QueryApi apiInstance = new QueryApi(defaultClient);
+        Integer integerQuery = 56; // Integer | 
+        Boolean booleanQuery = true; // Boolean | 
+        String stringQuery = "stringQuery_example"; // String | 
+        try {
+            ApiResponse<String> response = apiInstance.testQueryIntegerBooleanStringWithHttpInfo(integerQuery, booleanQuery, stringQuery);
+            System.out.println("Status code: " + response.getStatusCode());
+            System.out.println("Response headers: " + response.getHeaders());
+            System.out.println("Response body: " + response.getData());
+        } catch (ApiException e) {
+            System.err.println("Exception when calling QueryApi#testQueryIntegerBooleanString");
+            System.err.println("Status code: " + e.getCode());
+            System.err.println("Response headers: " + e.getResponseHeaders());
+            System.err.println("Reason: " + e.getResponseBody());
+            e.printStackTrace();
+        }
+    }
+}
+```
+
+### Parameters
+
+
+| Name | Type | Description  | Notes |
+|------------- | ------------- | ------------- | -------------|
+| **integerQuery** | **Integer**|  | [optional] |
+| **booleanQuery** | **Boolean**|  | [optional] |
+| **stringQuery** | **String**|  | [optional] |
+
+### Return type
+
+ApiResponse<**String**>
+
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+- **Content-Type**: Not defined
+- **Accept**: text/plain
+
+### HTTP response details
+| Status code | Description | Response headers |
+|-------------|-------------|------------------|
+| **200** | Successful operation |  -  |
+
+
 ## testQueryStyleFormExplodeTrueArrayString
 
 > String testQueryStyleFormExplodeTrueArrayString(queryObject)

samples/client/echo_api/java/native/src/main/java/org/openapitools/client/api/PathApi.java

@@ -0,0 +1,164 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.ApiException;
+import org.openapitools.client.ApiResponse;
+import org.openapitools.client.Pair;
+
+
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.time.Duration;
+
+import java.util.ArrayList;
+import java.util.StringJoiner;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.function.Consumer;
+
+@javax.annotation.processing.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
+public class PathApi {
+  private final HttpClient memberVarHttpClient;
+  private final ObjectMapper memberVarObjectMapper;
+  private final String memberVarBaseUri;
+  private final Consumer<HttpRequest.Builder> memberVarInterceptor;
+  private final Duration memberVarReadTimeout;
+  private final Consumer<HttpResponse<InputStream>> memberVarResponseInterceptor;
+  private final Consumer<HttpResponse<String>> memberVarAsyncResponseInterceptor;
+
+  public PathApi() {
+    this(new ApiClient());
+  }
+
+  public PathApi(ApiClient apiClient) {
+    memberVarHttpClient = apiClient.getHttpClient();
+    memberVarObjectMapper = apiClient.getObjectMapper();
+    memberVarBaseUri = apiClient.getBaseUri();
+    memberVarInterceptor = apiClient.getRequestInterceptor();
+    memberVarReadTimeout = apiClient.getReadTimeout();
+    memberVarResponseInterceptor = apiClient.getResponseInterceptor();
+    memberVarAsyncResponseInterceptor = apiClient.getAsyncResponseInterceptor();
+  }
+
+  protected ApiException getApiException(String operationId, HttpResponse<InputStream> response) throws IOException {
+    String body = response.body() == null ? null : new String(response.body().readAllBytes());
+    String message = formatExceptionMessage(operationId, response.statusCode(), body);
+    return new ApiException(response.statusCode(), message, response.headers(), body);
+  }
+
+  private String formatExceptionMessage(String operationId, int statusCode, String body) {
+    if (body == null || body.isEmpty()) {
+      body = "[no body]";
+    }
+    return operationId + " call failed with: " + statusCode + " - " + body;
+  }
+
+  /**
+   * Test path parameter(s)
+   * Test path parameter(s)
+   * @param pathString  (required)
+   * @param pathInteger  (required)
+   * @return String
+   * @throws ApiException if fails to make API call
+   */
+  public String testsPathStringPathStringIntegerPathInteger(String pathString, Integer pathInteger) throws ApiException {
+    ApiResponse<String> localVarResponse = testsPathStringPathStringIntegerPathIntegerWithHttpInfo(pathString, pathInteger);
+    return localVarResponse.getData();
+  }
+
+  /**
+   * Test path parameter(s)
+   * Test path parameter(s)
+   * @param pathString  (required)
+   * @param pathInteger  (required)
+   * @return ApiResponse&lt;String&gt;
+   * @throws ApiException if fails to make API call
+   */
+  public ApiResponse<String> testsPathStringPathStringIntegerPathIntegerWithHttpInfo(String pathString, Integer pathInteger) throws ApiException {
+    HttpRequest.Builder localVarRequestBuilder = testsPathStringPathStringIntegerPathIntegerRequestBuilder(pathString, pathInteger);
+    try {
+      HttpResponse<InputStream> localVarResponse = memberVarHttpClient.send(
+          localVarRequestBuilder.build(),
+          HttpResponse.BodyHandlers.ofInputStream());
+      if (memberVarResponseInterceptor != null) {
+        memberVarResponseInterceptor.accept(localVarResponse);
+      }
+      try {
+        if (localVarResponse.statusCode()/ 100 != 2) {
+          throw getApiException("testsPathStringPathStringIntegerPathInteger", localVarResponse);
+        }
+        // for plain text response
+        InputStream responseBody = localVarResponse.body();
+        if (localVarResponse.headers().map().containsKey("Content-Type") &&
+                "text/plain".equalsIgnoreCase(localVarResponse.headers().map().get("Content-Type").get(0))) {
+          java.util.Scanner s = new java.util.Scanner(responseBody).useDelimiter("\\A");
+          String responseBodyText = s.hasNext() ? s.next() : "";
+          return new ApiResponse<String>(
+                  localVarResponse.statusCode(),
+                  localVarResponse.headers().map(),
+                  responseBodyText
+          );
+        } else {
+            throw new RuntimeException("Error! The response Content-Type is supposed to be `text/plain` but it's not: " + localVarResponse);
+        }
+      } finally {
+      }
+    } catch (IOException e) {
+      throw new ApiException(e);
+    }
+    catch (InterruptedException e) {
+      Thread.currentThread().interrupt();
+      throw new ApiException(e);
+    }
+  }
+
+  private HttpRequest.Builder testsPathStringPathStringIntegerPathIntegerRequestBuilder(String pathString, Integer pathInteger) throws ApiException {
+    // verify the required parameter 'pathString' is set
+    if (pathString == null) {
+      throw new ApiException(400, "Missing the required parameter 'pathString' when calling testsPathStringPathStringIntegerPathInteger");
+    }
+    // verify the required parameter 'pathInteger' is set
+    if (pathInteger == null) {
+      throw new ApiException(400, "Missing the required parameter 'pathInteger' when calling testsPathStringPathStringIntegerPathInteger");
+    }
+
+    HttpRequest.Builder localVarRequestBuilder = HttpRequest.newBuilder();
+
+    String localVarPath = "/path/string/{path_string}/integer/{path_integer}"
+        .replace("{path_string}", ApiClient.urlEncode(pathString.toString()))
+        .replace("{path_integer}", ApiClient.urlEncode(pathInteger.toString()));
+
+    localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));
+
+    localVarRequestBuilder.header("Accept", "text/plain");
+
+    localVarRequestBuilder.method("GET", HttpRequest.BodyPublishers.noBody());
+    if (memberVarReadTimeout != null) {
+      localVarRequestBuilder.timeout(memberVarReadTimeout);
+    }
+    if (memberVarInterceptor != null) {
+      memberVarInterceptor.accept(localVarRequestBuilder);
+    }
+    return localVarRequestBuilder;
+  }
+}

samples/client/echo_api/java/native/src/main/java/org/openapitools/client/api/QueryApi.java

@@ -75,6 +75,97 @@ public class QueryApi {
     return operationId + " call failed with: " + statusCode + " - " + body;
   }
 
+  /**
+   * Test query parameter(s)
+   * Test query parameter(s)
+   * @param integerQuery  (optional)
+   * @param booleanQuery  (optional)
+   * @param stringQuery  (optional)
+   * @return String
+   * @throws ApiException if fails to make API call
+   */
+  public String testQueryIntegerBooleanString(Integer integerQuery, Boolean booleanQuery, String stringQuery) throws ApiException {
+    ApiResponse<String> localVarResponse = testQueryIntegerBooleanStringWithHttpInfo(integerQuery, booleanQuery, stringQuery);
+    return localVarResponse.getData();
+  }
+
+  /**
+   * Test query parameter(s)
+   * Test query parameter(s)
+   * @param integerQuery  (optional)
+   * @param booleanQuery  (optional)
+   * @param stringQuery  (optional)
+   * @return ApiResponse&lt;String&gt;
+   * @throws ApiException if fails to make API call
+   */
+  public ApiResponse<String> testQueryIntegerBooleanStringWithHttpInfo(Integer integerQuery, Boolean booleanQuery, String stringQuery) throws ApiException {
+    HttpRequest.Builder localVarRequestBuilder = testQueryIntegerBooleanStringRequestBuilder(integerQuery, booleanQuery, stringQuery);
+    try {
+      HttpResponse<InputStream> localVarResponse = memberVarHttpClient.send(
+          localVarRequestBuilder.build(),
+          HttpResponse.BodyHandlers.ofInputStream());
+      if (memberVarResponseInterceptor != null) {
+        memberVarResponseInterceptor.accept(localVarResponse);
+      }
+      try {
+        if (localVarResponse.statusCode()/ 100 != 2) {
+          throw getApiException("testQueryIntegerBooleanString", localVarResponse);
+        }
+        // for plain text response
+        InputStream responseBody = localVarResponse.body();
+        if (localVarResponse.headers().map().containsKey("Content-Type") &&
+                "text/plain".equalsIgnoreCase(localVarResponse.headers().map().get("Content-Type").get(0))) {
+          java.util.Scanner s = new java.util.Scanner(responseBody).useDelimiter("\\A");
+          String responseBodyText = s.hasNext() ? s.next() : "";
+          return new ApiResponse<String>(
+                  localVarResponse.statusCode(),
+                  localVarResponse.headers().map(),
+                  responseBodyText
+          );
+        } else {
+            throw new RuntimeException("Error! The response Content-Type is supposed to be `text/plain` but it's not: " + localVarResponse);
+        }
+      } finally {
+      }
+    } catch (IOException e) {
+      throw new ApiException(e);
+    }
+    catch (InterruptedException e) {
+      Thread.currentThread().interrupt();
+      throw new ApiException(e);
+    }
+  }
+
+  private HttpRequest.Builder testQueryIntegerBooleanStringRequestBuilder(Integer integerQuery, Boolean booleanQuery, String stringQuery) throws ApiException {
+
+    HttpRequest.Builder localVarRequestBuilder = HttpRequest.newBuilder();
+
+    String localVarPath = "/query/integer/boolean/string";
+
+    List<Pair> localVarQueryParams = new ArrayList<>();
+    localVarQueryParams.addAll(ApiClient.parameterToPairs("integer_query", integerQuery));
+    localVarQueryParams.addAll(ApiClient.parameterToPairs("boolean_query", booleanQuery));
+    localVarQueryParams.addAll(ApiClient.parameterToPairs("string_query", stringQuery));
+
+    if (!localVarQueryParams.isEmpty()) {
+      StringJoiner queryJoiner = new StringJoiner("&");
+      localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
+    } else {
+      localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));
+    }
+
+    localVarRequestBuilder.header("Accept", "text/plain");
+
+    localVarRequestBuilder.method("GET", HttpRequest.BodyPublishers.noBody());
+    if (memberVarReadTimeout != null) {
+      localVarRequestBuilder.timeout(memberVarReadTimeout);
+    }
+    if (memberVarInterceptor != null) {
+      memberVarInterceptor.accept(localVarRequestBuilder);
+    }
+    return localVarRequestBuilder;
+  }
   /**
    * Test query parameter(s)
    * Test query parameter(s)

samples/client/echo_api/java/native/src/test/java/org/openapitools/client/api/PathApiTest.java

@@ -0,0 +1,54 @@
+/*
+ * Echo Server API
+ * Echo Server API
+ *
+ * The version of the OpenAPI document: 0.1.0
+ * Contact: team@openapitools.org
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package org.openapitools.client.api;
+
+import org.openapitools.client.ApiException;
+import org.junit.Test;
+import org.junit.Ignore;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+
+/**
+ * API tests for PathApi
+ */
+@Ignore
+public class PathApiTest {
+
+    private final PathApi api = new PathApi();
+
+    
+    /**
+     * Test path parameter(s)
+     *
+     * Test path parameter(s)
+     *
+     * @throws ApiException
+     *          if the Api call fails
+     */
+    @Test
+    public void testsPathStringPathStringIntegerPathIntegerTest() throws ApiException {
+        String pathString = null;
+        Integer pathInteger = null;
+        String response = 
+        api.testsPathStringPathStringIntegerPathInteger(pathString, pathInteger);
+        
+        // TODO: test validations
+    }
+    
+}

samples/client/petstore/java/apache-httpclient/src/main/java/org/openapitools/client/ApiClient.java

@@ -596,9 +596,11 @@ public class ApiClient extends JavaTimeFormatter {
     List<Pair> params = new ArrayList<Pair>();
 
     // preconditions
-    if (name == null || name.isEmpty() || value == null || value instanceof Collection) return params;
+    if (name == null || name.isEmpty() || value == null || value instanceof Collection) {
+      return params;
+    }
 
-    params.add(new Pair(name, parameterToString(value)));
+    params.add(new Pair(name, escapeString(parameterToString(value))));
     return params;
   }
 
@@ -845,6 +847,10 @@ public class ApiClient extends JavaTimeFormatter {
     if (mimeType == null || isJsonMime(mimeType)) {
       // Assume json if no mime type
       return objectMapper.readValue(entity.getContent(), valueType);
+    } else if ("text/plain".equalsIgnoreCase(mimeType)) {
+      // convert input stream to string
+      java.util.Scanner s = new java.util.Scanner(entity.getContent()).useDelimiter("\\A");
+      return (T) (s.hasNext() ? s.next() : "");
     } else {
       throw new ApiException(
           "Deserialization for content type '" + mimeType + "' not supported for type '" + valueType + "'",
@@ -933,7 +939,8 @@ public class ApiClient extends JavaTimeFormatter {
             url.append("&");
           }
           String value = parameterToString(param.getValue());
-          url.append(escapeString(param.getName())).append("=").append(escapeString(value));
+          // query parameter value already escaped as part of parameterToPair
+          url.append(escapeString(param.getName())).append("=").append(value);
         }
       }
     }