Add deepObject query string support in Java native client (#14378)

* add deepObject query string support in java native client

* fix array of query parameters

* minor fix

* update samples

* fix test

modules/openapi-generator/src/main/resources/Java/libraries/native/api.mustache

@@ -338,21 +338,24 @@ public class {{classname}} {
 
     {{#hasQueryParams}}
     {{javaUtilPrefix}}List<Pair> localVarQueryParams = new {{javaUtilPrefix}}ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
     {{#queryParams}}
+    localVarQueryParameterBaseName = "{{{baseName}}}";
       {{#collectionFormat}}
     localVarQueryParams.addAll(ApiClient.parameterToPairs("{{{collectionFormat}}}", "{{baseName}}", {{paramName}}));
       {{/collectionFormat}}
       {{^collectionFormat}}
         {{#isDeepObject}}
     if ({{paramName}} != null) {
-          {{#items.vars}}
             {{#isArray}}
-      localVarQueryParams.addAll(ApiClient.parameterToPairs("csv", "{{paramName}}[{{name}}]", {{paramName}}.{{getter}}()));
+      for (int i=0; i < {{paramName}}.size(); i++) {
+        localVarQueryDeepObjectStringJoiner.add({{paramName}}.get(i).toUrlQueryString(String.format("{{baseName}}[%d]", i)));
+      }
             {{/isArray}}
             {{^isArray}}
-      localVarQueryParams.addAll(ApiClient.parameterToPairs("{{paramName}}[{{name}}]", {{paramName}}.{{getter}}()));
+      localVarQueryDeepObjectStringJoiner.add({{paramName}}.toUrlQueryString("{{baseName}}"));
             {{/isArray}}
-          {{/items.vars}}
     }
         {{/isDeepObject}}
         {{^isDeepObject}}
@@ -378,9 +381,12 @@ public class {{classname}} {
       {{/collectionFormat}}
     {{/queryParams}}
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       {{javaUtilPrefix}}StringJoiner queryJoiner = new {{javaUtilPrefix}}StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));

modules/openapi-generator/src/main/resources/Java/libraries/native/model.mustache

@@ -16,10 +16,13 @@ import com.fasterxml.jackson.annotation.JsonAnySetter;
 {{/additionalPropertiesType}}
 {{/model}}
 {{/models}}
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 {{#imports}}
 import {{import}};
 {{/imports}}

modules/openapi-generator/src/main/resources/Java/libraries/native/modelEnum.mustache

@@ -0,0 +1,115 @@
+{{#jackson}}
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonValue;
+{{/jackson}}
+{{#gson}}
+import java.io.IOException;
+import com.google.gson.TypeAdapter;
+import com.google.gson.annotations.JsonAdapter;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+{{/gson}}
+
+/**
+ * {{description}}{{^description}}Gets or Sets {{{name}}}{{/description}}
+ */
+{{#gson}}
+@JsonAdapter({{{datatypeWithEnum}}}{{^datatypeWithEnum}}{{{classname}}}{{/datatypeWithEnum}}.Adapter.class)
+{{/gson}}
+{{#jsonb}}
+@JsonbTypeSerializer({{datatypeWithEnum}}.Serializer.class)
+@JsonbTypeDeserializer({{datatypeWithEnum}}.Deserializer.class)
+{{/jsonb}}
+{{>additionalEnumTypeAnnotations}}public enum {{{datatypeWithEnum}}}{{^datatypeWithEnum}}{{{classname}}}{{/datatypeWithEnum}} {
+  {{#allowableValues}}{{#enumVars}}
+    {{#enumDescription}}
+  /**
+   * {{.}}
+   */
+     {{/enumDescription}}
+  {{#withXml}}
+  @XmlEnumValue({{#isInteger}}"{{/isInteger}}{{#isDouble}}"{{/isDouble}}{{#isLong}}"{{/isLong}}{{#isFloat}}"{{/isFloat}}{{{value}}}{{#isInteger}}"{{/isInteger}}{{#isDouble}}"{{/isDouble}}{{#isLong}}"{{/isLong}}{{#isFloat}}"{{/isFloat}})
+  {{/withXml}}
+  {{{name}}}({{{value}}}){{^-last}},
+  {{/-last}}{{#-last}};{{/-last}}{{/enumVars}}{{/allowableValues}}
+
+  private {{{dataType}}} value;
+
+  {{{datatypeWithEnum}}}{{^datatypeWithEnum}}{{{classname}}}{{/datatypeWithEnum}}({{{dataType}}} value) {
+    this.value = value;
+  }
+
+{{#jackson}}
+  @JsonValue
+{{/jackson}}
+  public {{{dataType}}} getValue() {
+    return value;
+  }
+
+  @Override
+  public String toString() {
+    return String.valueOf(value);
+  }
+
+{{#jackson}}
+  @JsonCreator
+{{/jackson}}
+  public static {{{datatypeWithEnum}}}{{^datatypeWithEnum}}{{{classname}}}{{/datatypeWithEnum}} fromValue({{{dataType}}} value) {
+    for ({{{datatypeWithEnum}}}{{^datatypeWithEnum}}{{{classname}}}{{/datatypeWithEnum}} b : {{{datatypeWithEnum}}}{{^datatypeWithEnum}}{{{classname}}}{{/datatypeWithEnum}}.values()) {
+      if (b.value.equals(value)) {
+        return b;
+      }
+    }
+    {{#isNullable}}return null;{{/isNullable}}{{^isNullable}}{{#enumUnknownDefaultCase}}{{#allowableValues}}{{#enumVars}}{{#-last}}return {{{name}}};{{/-last}}{{/enumVars}}{{/allowableValues}}{{/enumUnknownDefaultCase}}{{^enumUnknownDefaultCase}}throw new IllegalArgumentException("Unexpected value '" + value + "'");{{/enumUnknownDefaultCase}}{{/isNullable}}
+  }
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    return String.format("%s=%s", prefix, this.toString());
+  }
+
+{{#gson}}
+
+  public static class Adapter extends TypeAdapter<{{{datatypeWithEnum}}}{{^datatypeWithEnum}}{{{classname}}}{{/datatypeWithEnum}}> {
+    @Override
+    public void write(final JsonWriter jsonWriter, final {{{datatypeWithEnum}}}{{^datatypeWithEnum}}{{{classname}}}{{/datatypeWithEnum}} enumeration) throws IOException {
+      jsonWriter.value(enumeration.getValue());
+    }
+
+    @Override
+    public {{{datatypeWithEnum}}}{{^datatypeWithEnum}}{{{classname}}}{{/datatypeWithEnum}} read(final JsonReader jsonReader) throws IOException {
+      {{^isNumber}}{{{dataType}}}{{/isNumber}}{{#isNumber}}String{{/isNumber}} value = jsonReader.{{#isNumber}}nextString(){{/isNumber}}{{#isInteger}}nextInt(){{/isInteger}}{{^isNumber}}{{^isInteger}}next{{{dataType}}}(){{/isInteger}}{{/isNumber}};
+      return {{{datatypeWithEnum}}}{{^datatypeWithEnum}}{{{classname}}}{{/datatypeWithEnum}}.fromValue({{#isNumber}}new BigDecimal({{/isNumber}}value{{#isNumber}}){{/isNumber}});
+    }
+  }
+{{/gson}}
+{{#jsonb}}
+  public static final class Deserializer implements JsonbDeserializer<{{datatypeWithEnum}}> {
+    @Override
+    public {{datatypeWithEnum}} deserialize(JsonParser parser, DeserializationContext ctx, Type rtType) {
+      for ({{{datatypeWithEnum}}}{{^datatypeWithEnum}}{{{classname}}}{{/datatypeWithEnum}} b : {{{datatypeWithEnum}}}{{^datatypeWithEnum}}{{{classname}}}{{/datatypeWithEnum}}.values()) {
+        if (String.valueOf(b.value).equals(parser.getString())) {
+          return b;
+        }
+      }
+      {{#useNullForUnknownEnumValue}}return null;{{/useNullForUnknownEnumValue}}{{^useNullForUnknownEnumValue}}throw new IllegalArgumentException("Unexpected value '" + parser.getString() + "'");{{/useNullForUnknownEnumValue}}
+    }
+  }
+
+  public static final class Serializer implements JsonbSerializer<{{datatypeWithEnum}}> {
+    @Override
+    public void serialize({{datatypeWithEnum}} obj, JsonGenerator generator, SerializationContext ctx) {
+      generator.write(obj.value);
+    }
+  }
+{{/jsonb}}
+}

modules/openapi-generator/src/main/resources/Java/libraries/native/pojo.mustache

@@ -349,6 +349,131 @@ public class {{classname}} {{#parent}}extends {{{.}}} {{/parent}}{{#vendorExtens
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    {{#allVars}}
+    // add `{{baseName}}` to the URL query string
+    {{#isArray}}
+    {{#items.isPrimitiveType}}
+    {{#uniqueItems}}
+    if ({{getter}}() != null) {
+      int i = 0;
+      for ({{items.dataType}} _item : {{getter}}()) {
+        joiner.add(String.format("%s[{{baseName}}][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(_item), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+      i++;
+    }
+    {{/uniqueItems}}
+    {{^uniqueItems}}
+    if ({{getter}}() != null) {
+      for (int i = 0; i < {{getter}}().size(); i++) {
+        joiner.add(String.format("%s[{{baseName}}][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf({{getter}}().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+    {{/uniqueItems}}
+    {{/items.isPrimitiveType}}
+    {{^items.isPrimitiveType}}
+    {{#items.isModel}}
+    {{#uniqueItems}}
+    if ({{getter}}() != null) {
+      int i = 0;
+      for ({{items.dataType}} _item : {{getter}}()) {
+        if ({{getter}}().get(i) != null) {
+          joiner.add(_item.toUrlQueryString(String.format("%s[{{baseName}}][%d]", prefix, i)));
+        }
+      }
+      i++;
+    }
+    {{/uniqueItems}}
+    {{^uniqueItems}}
+    if ({{getter}}() != null) {
+      for (int i = 0; i < {{getter}}().size(); i++) {
+        if ({{getter}}().get(i) != null) {
+          joiner.add({{getter}}().get(i).toUrlQueryString(String.format("%s[{{baseName}}][%d]", prefix, i)));
+        }
+      }
+    }
+    {{/uniqueItems}}
+    {{/items.isModel}}
+    {{^items.isModel}}
+    {{#uniqueItems}}
+    if ({{getter}}() != null) {
+      int i = 0;
+      for ({{items.dataType}} _item : {{getter}}()) {
+        if (_item != null) {
+          joiner.add(String.format("%s[{{baseName}}][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(_item), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+        }
+        i++;
+      }
+    }
+    {{/uniqueItems}}
+    {{^uniqueItems}}
+    if ({{getter}}() != null) {
+      for (int i = 0; i < {{getter}}().size(); i++) {
+        if ({{getter}}().get(i) != null) {
+          joiner.add(String.format("%s[{{baseName}}][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf({{getter}}().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+        }
+      }
+    }
+    {{/uniqueItems}}
+    {{/items.isModel}}
+    {{/items.isPrimitiveType}}
+    {{/isArray}}
+    {{^isArray}}
+    {{#isMap}}
+    {{#items.isPrimitiveType}}
+    if ({{getter}}() != null) {
+      for (String _key : {{getter}}().keySet()) {
+        joiner.add(String.format("%s[{{baseName}}][%s]=%s", prefix, {{getter}}().get(_key), URLEncoder.encode(String.valueOf({{getter}}().get(_key)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+    {{/items.isPrimitiveType}}
+    {{^items.isPrimitiveType}}
+    if ({{getter}}() != null) {
+      for (String _key : {{getter}}().keySet()) {
+        if ({{getter}}().get(_key) != null) {
+          joiner.add({{getter}}().get(_key).toUrlQueryString(String.format("%s[{{baseName}}][%s]", prefix, _key)));
+        }
+      }
+    }
+    {{/items.isPrimitiveType}}
+    {{/isMap}}
+    {{^isMap}}
+    {{#isPrimitiveType}}
+    if ({{getter}}() != null) {
+      joiner.add(String.format("%s[{{{baseName}}}]=%s", prefix, URLEncoder.encode(String.valueOf({{{getter}}}()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+    {{/isPrimitiveType}}
+    {{^isPrimitiveType}}
+    {{#isModel}}
+    if ({{getter}}() != null) {
+      joiner.add({{getter}}().toUrlQueryString(prefix + "[{{{baseName}}}]"));
+    }
+    {{/isModel}}
+    {{^isModel}}
+    if ({{getter}}() != null) {
+      joiner.add(String.format("%s[{{{baseName}}}]=%s", prefix, URLEncoder.encode(String.valueOf({{{getter}}}()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+    {{/isModel}}
+    {{/isPrimitiveType}}
+    {{/isMap}}
+    {{/isArray}}
+
+    {{/allVars}}
+    return joiner.toString();
+  }
 {{#parcelableModel}}
 
   public void writeToParcel(Parcel out, int flags) {

modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaClientDeepObjectTest.java

@@ -58,9 +58,7 @@ public class JavaClientDeepObjectTest {
         generator.opts(input).generate();
 
         assertFileContains(Paths.get(outputPath + "/src/main/java/org/openapitools/client/api/DefaultApi.java"),
-                "options[id]", "options[name]", "options[status]",
-                "\"csv\", \"options[tags]\"",
-                "\"csv\", \"options[photoUrls]\"",
-                "inputOptions[a]", "inputOptions[b]", "\"csv\", \"inputOptions[c]\"");
+                "options.toUrlQueryString(\"options\")",
+                "inputOptions.toUrlQueryString(\"inputOptions\"))");
     }
 }

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

@@ -137,6 +137,27 @@ paths:
             text/plain:
               schema:
                 type: string
+  /query/style_deepObject/explode_true/object:
+    get:
+      tags:
+        - query
+      summary: Test query parameter(s)
+      description: Test query parameter(s)
+      operationId: test/query/style_deepObject/explode_true/object
+      parameters:
+      - in: query
+        name: query_object
+        style: deepObject
+        explode: true #default
+        schema:
+          $ref: '#/components/schemas/Pet'
+      responses:
+        '200':
+          description: Successful operation
+          content:
+            text/plain:
+              schema:
+                type: string
   /echo/body/Pet:
     post:
       tags:

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

@@ -109,6 +109,7 @@ Class | Method | HTTP request | Description
 *BodyApi* | [**testEchoBodyPet**](docs/BodyApi.md#testEchoBodyPet) | **POST** /echo/body/Pet | Test body parameter(s)
 *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* | [**testQueryStyleDeepObjectExplodeTrueObject**](docs/QueryApi.md#testQueryStyleDeepObjectExplodeTrueObject) | **GET** /query/style_deepObject/explode_true/object | 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)
 

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

@@ -124,6 +124,29 @@ paths:
       tags:
       - query
       x-accepts: text/plain
+  /query/style_deepObject/explode_true/object:
+    get:
+      description: Test query parameter(s)
+      operationId: test/query/style_deepObject/explode_true/object
+      parameters:
+      - explode: true
+        in: query
+        name: query_object
+        required: false
+        schema:
+          $ref: '#/components/schemas/Pet'
+        style: deepObject
+      responses:
+        "200":
+          content:
+            text/plain:
+              schema:
+                type: string
+          description: Successful operation
+      summary: Test query parameter(s)
+      tags:
+      - query
+      x-accepts: text/plain
   /echo/body/Pet:
     post:
       description: Test body parameter(s)

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

@@ -5,6 +5,7 @@ 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) |
+| [**testQueryStyleDeepObjectExplodeTrueObject**](QueryApi.md#testQueryStyleDeepObjectExplodeTrueObject) | **GET** /query/style_deepObject/explode_true/object | 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) |
 
@@ -80,6 +81,72 @@ No authorization required
 | **200** | Successful operation |  -  |
 
 
+## testQueryStyleDeepObjectExplodeTrueObject
+
+> String testQueryStyleDeepObjectExplodeTrueObject(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.testQueryStyleDeepObjectExplodeTrueObject(queryObject);
+            System.out.println(result);
+        } catch (ApiException e) {
+            System.err.println("Exception when calling QueryApi#testQueryStyleDeepObjectExplodeTrueObject");
+            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 |  -  |
+
+
 ## testQueryStyleFormExplodeTrueArrayString
 
 > String testQueryStyleFormExplodeTrueArrayString(queryObject)

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

@@ -77,6 +77,58 @@ public class QueryApi {
     
     
     
+    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 testQueryStyleDeepObjectExplodeTrueObject(Pet queryObject) throws ApiException {
+    Object localVarPostBody = null;
+    
+    // create path and map variables
+    String localVarPath = "/query/style_deepObject/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("query_object", queryObject));
+    
+    
+    
     final String[] localVarAccepts = {
       "text/plain"
     };

samples/client/echo_api/java/feign-gson/api/openapi.yaml

@@ -124,6 +124,29 @@ paths:
       tags:
       - query
       x-accepts: text/plain
+  /query/style_deepObject/explode_true/object:
+    get:
+      description: Test query parameter(s)
+      operationId: test/query/style_deepObject/explode_true/object
+      parameters:
+      - explode: true
+        in: query
+        name: query_object
+        required: false
+        schema:
+          $ref: '#/components/schemas/Pet'
+        style: deepObject
+      responses:
+        "200":
+          content:
+            text/plain:
+              schema:
+                type: string
+          description: Successful operation
+      summary: Test query parameter(s)
+      tags:
+      - query
+      x-accepts: text/plain
   /echo/body/Pet:
     post:
       description: Test body parameter(s)

samples/client/echo_api/java/feign-gson/src/main/java/org/openapitools/client/api/QueryApi.java

@@ -110,6 +110,83 @@ public interface QueryApi extends ApiClient.Api {
     }
   }
 
+  /**
+   * Test query parameter(s)
+   * Test query parameter(s)
+   * @param queryObject  (optional)
+   * @return String
+   */
+  @RequestLine("GET /query/style_deepObject/explode_true/object?query_object={queryObject}")
+  @Headers({
+    "Accept: text/plain",
+  })
+  String testQueryStyleDeepObjectExplodeTrueObject(@Param("queryObject") Pet queryObject);
+
+  /**
+   * Test query parameter(s)
+   * Similar to <code>testQueryStyleDeepObjectExplodeTrueObject</code> but it also returns the http response headers .
+   * Test query parameter(s)
+   * @param queryObject  (optional)
+   * @return A ApiResponse that wraps the response boyd and the http headers.
+   */
+  @RequestLine("GET /query/style_deepObject/explode_true/object?query_object={queryObject}")
+  @Headers({
+    "Accept: text/plain",
+  })
+  ApiResponse<String> testQueryStyleDeepObjectExplodeTrueObjectWithHttpInfo(@Param("queryObject") Pet queryObject);
+
+
+  /**
+   * Test query parameter(s)
+   * Test query parameter(s)
+   * Note, this is equivalent to the other <code>testQueryStyleDeepObjectExplodeTrueObject</code> method,
+   * but with the query parameters collected into a single Map parameter. This
+   * is convenient for services with optional query parameters, especially when
+   * used with the {@link TestQueryStyleDeepObjectExplodeTrueObjectQueryParams} class that allows for
+   * building up this map in a fluent style.
+   * @param queryParams Map of query parameters as name-value pairs
+   *   <p>The following elements may be specified in the query map:</p>
+   *   <ul>
+   *   <li>queryObject -  (optional)</li>
+   *   </ul>
+   * @return String
+   */
+  @RequestLine("GET /query/style_deepObject/explode_true/object?query_object={queryObject}")
+  @Headers({
+  "Accept: text/plain",
+  })
+  String testQueryStyleDeepObjectExplodeTrueObject(@QueryMap(encoded=true) TestQueryStyleDeepObjectExplodeTrueObjectQueryParams queryParams);
+
+  /**
+  * Test query parameter(s)
+  * Test query parameter(s)
+  * Note, this is equivalent to the other <code>testQueryStyleDeepObjectExplodeTrueObject</code> that receives the query parameters as a map,
+  * but this one also exposes the Http response headers
+      * @param queryParams Map of query parameters as name-value pairs
+      *   <p>The following elements may be specified in the query map:</p>
+      *   <ul>
+          *   <li>queryObject -  (optional)</li>
+      *   </ul>
+          * @return String
+      */
+      @RequestLine("GET /query/style_deepObject/explode_true/object?query_object={queryObject}")
+      @Headers({
+    "Accept: text/plain",
+      })
+   ApiResponse<String> testQueryStyleDeepObjectExplodeTrueObjectWithHttpInfo(@QueryMap(encoded=true) TestQueryStyleDeepObjectExplodeTrueObjectQueryParams queryParams);
+
+
+   /**
+   * A convenience class for generating query parameters for the
+   * <code>testQueryStyleDeepObjectExplodeTrueObject</code> method in a fluent style.
+   */
+  public static class TestQueryStyleDeepObjectExplodeTrueObjectQueryParams extends HashMap<String, Object> {
+    public TestQueryStyleDeepObjectExplodeTrueObjectQueryParams queryObject(final Pet value) {
+      put("query_object", EncodingUtils.encode(value));
+      return this;
+    }
+  }
+
   /**
    * Test query parameter(s)
    * Test query parameter(s)

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

@@ -111,6 +111,8 @@ Class | Method | HTTP request | Description
 *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* | [**testQueryStyleDeepObjectExplodeTrueObject**](docs/QueryApi.md#testQueryStyleDeepObjectExplodeTrueObject) | **GET** /query/style_deepObject/explode_true/object | Test query parameter(s)
+*QueryApi* | [**testQueryStyleDeepObjectExplodeTrueObjectWithHttpInfo**](docs/QueryApi.md#testQueryStyleDeepObjectExplodeTrueObjectWithHttpInfo) | **GET** /query/style_deepObject/explode_true/object | 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

@@ -124,6 +124,29 @@ paths:
       tags:
       - query
       x-accepts: text/plain
+  /query/style_deepObject/explode_true/object:
+    get:
+      description: Test query parameter(s)
+      operationId: test/query/style_deepObject/explode_true/object
+      parameters:
+      - explode: true
+        in: query
+        name: query_object
+        required: false
+        schema:
+          $ref: '#/components/schemas/Pet'
+        style: deepObject
+      responses:
+        "200":
+          content:
+            text/plain:
+              schema:
+                type: string
+          description: Successful operation
+      summary: Test query parameter(s)
+      tags:
+      - query
+      x-accepts: text/plain
   /echo/body/Pet:
     post:
       description: Test body parameter(s)

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

@@ -6,6 +6,8 @@ All URIs are relative to *http://localhost:3000*
 |------------- | ------------- | -------------|
 | [**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) |
+| [**testQueryStyleDeepObjectExplodeTrueObject**](QueryApi.md#testQueryStyleDeepObjectExplodeTrueObject) | **GET** /query/style_deepObject/explode_true/object | Test query parameter(s) |
+| [**testQueryStyleDeepObjectExplodeTrueObjectWithHttpInfo**](QueryApi.md#testQueryStyleDeepObjectExplodeTrueObjectWithHttpInfo) | **GET** /query/style_deepObject/explode_true/object | 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) |
@@ -155,6 +157,140 @@ No authorization required
 | **200** | Successful operation |  -  |
 
 
+## testQueryStyleDeepObjectExplodeTrueObject
+
+> String testQueryStyleDeepObjectExplodeTrueObject(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.testQueryStyleDeepObjectExplodeTrueObject(queryObject);
+            System.out.println(result);
+        } catch (ApiException e) {
+            System.err.println("Exception when calling QueryApi#testQueryStyleDeepObjectExplodeTrueObject");
+            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 |  -  |
+
+## testQueryStyleDeepObjectExplodeTrueObjectWithHttpInfo
+
+> ApiResponse<String> testQueryStyleDeepObjectExplodeTrueObject testQueryStyleDeepObjectExplodeTrueObjectWithHttpInfo(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.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);
+        Pet queryObject = new HashMap(); // Pet | 
+        try {
+            ApiResponse<String> response = apiInstance.testQueryStyleDeepObjectExplodeTrueObjectWithHttpInfo(queryObject);
+            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#testQueryStyleDeepObjectExplodeTrueObject");
+            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 |
+|------------- | ------------- | ------------- | -------------|
+| **queryObject** | [**Pet**](.md)|  | [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/QueryApi.java

@@ -142,13 +142,113 @@ public class QueryApi {
     String localVarPath = "/query/integer/boolean/string";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "integer_query";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("integer_query", integerQuery));
+    localVarQueryParameterBaseName = "boolean_query";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("boolean_query", booleanQuery));
+    localVarQueryParameterBaseName = "string_query";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("string_query", stringQuery));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
+      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)
+   * @param queryObject  (optional)
+   * @return String
+   * @throws ApiException if fails to make API call
+   */
+  public String testQueryStyleDeepObjectExplodeTrueObject(Pet queryObject) throws ApiException {
+    ApiResponse<String> localVarResponse = testQueryStyleDeepObjectExplodeTrueObjectWithHttpInfo(queryObject);
+    return localVarResponse.getData();
+  }
+
+  /**
+   * Test query parameter(s)
+   * Test query parameter(s)
+   * @param queryObject  (optional)
+   * @return ApiResponse&lt;String&gt;
+   * @throws ApiException if fails to make API call
+   */
+  public ApiResponse<String> testQueryStyleDeepObjectExplodeTrueObjectWithHttpInfo(Pet queryObject) throws ApiException {
+    HttpRequest.Builder localVarRequestBuilder = testQueryStyleDeepObjectExplodeTrueObjectRequestBuilder(queryObject);
+    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("testQueryStyleDeepObjectExplodeTrueObject", localVarResponse);
+        }
+        // for plain text response
+        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(localVarResponse.body()).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 testQueryStyleDeepObjectExplodeTrueObjectRequestBuilder(Pet queryObject) throws ApiException {
+
+    HttpRequest.Builder localVarRequestBuilder = HttpRequest.newBuilder();
+
+    String localVarPath = "/query/style_deepObject/explode_true/object";
+
+    List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "query_object";
+    if (queryObject != null) {
+      localVarQueryDeepObjectStringJoiner.add(queryObject.toUrlQueryString("query_object"));
+    }
+
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
+      StringJoiner queryJoiner = new StringJoiner("&");
+      localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));
@@ -228,11 +328,17 @@ public class QueryApi {
     String localVarPath = "/query/style_form/explode_true/array_string";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "query_object";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("multi", "values", queryObject.getValues()));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));
@@ -312,6 +418,9 @@ public class QueryApi {
     String localVarPath = "/query/style_form/explode_true/object";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "query_object";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("id", queryObject.getId()));
     localVarQueryParams.addAll(ApiClient.parameterToPairs("name", queryObject.getName()));
     localVarQueryParams.addAll(ApiClient.parameterToPairs("category", queryObject.getCategory()));
@@ -319,9 +428,12 @@ public class QueryApi {
     localVarQueryParams.addAll(ApiClient.parameterToPairs("multi", "tags", queryObject.getTags()));
     localVarQueryParams.addAll(ApiClient.parameterToPairs("status", queryObject.getStatus()));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));

samples/client/echo_api/java/native/src/main/java/org/openapitools/client/model/Category.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -135,5 +138,31 @@ public class Category {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `id` to the URL query string
+    if (getId() != null) {
+      joiner.add(String.format("%s[id]=%s", prefix, URLEncoder.encode(String.valueOf(getId()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `name` to the URL query string
+    if (getName() != null) {
+      joiner.add(String.format("%s[name]=%s", prefix, URLEncoder.encode(String.valueOf(getName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/echo_api/java/native/src/main/java/org/openapitools/client/model/Pet.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -313,5 +316,57 @@ public class Pet {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `id` to the URL query string
+    if (getId() != null) {
+      joiner.add(String.format("%s[id]=%s", prefix, URLEncoder.encode(String.valueOf(getId()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `name` to the URL query string
+    if (getName() != null) {
+      joiner.add(String.format("%s[name]=%s", prefix, URLEncoder.encode(String.valueOf(getName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `category` to the URL query string
+    if (getCategory() != null) {
+      joiner.add(getCategory().toUrlQueryString(prefix + "[category]"));
+    }
+
+    // add `photoUrls` to the URL query string
+    if (getPhotoUrls() != null) {
+      for (int i = 0; i < getPhotoUrls().size(); i++) {
+        joiner.add(String.format("%s[photoUrls][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getPhotoUrls().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    // add `tags` to the URL query string
+    if (getTags() != null) {
+      for (int i = 0; i < getTags().size(); i++) {
+        if (getTags().get(i) != null) {
+          joiner.add(getTags().get(i).toUrlQueryString(String.format("%s[tags][%d]", prefix, i)));
+        }
+      }
+    }
+
+    // add `status` to the URL query string
+    if (getStatus() != null) {
+      joiner.add(String.format("%s[status]=%s", prefix, URLEncoder.encode(String.valueOf(getStatus()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/echo_api/java/native/src/main/java/org/openapitools/client/model/Tag.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -135,5 +138,31 @@ public class Tag {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `id` to the URL query string
+    if (getId() != null) {
+      joiner.add(String.format("%s[id]=%s", prefix, URLEncoder.encode(String.valueOf(getId()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `name` to the URL query string
+    if (getName() != null) {
+      joiner.add(String.format("%s[name]=%s", prefix, URLEncoder.encode(String.valueOf(getName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/echo_api/java/native/src/main/java/org/openapitools/client/model/TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -114,5 +117,28 @@ public class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `values` to the URL query string
+    if (getValues() != null) {
+      for (int i = 0; i < getValues().size(); i++) {
+        joiner.add(String.format("%s[values][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getValues().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/echo_api/java/native/src/test/java/org/openapitools/client/CustomTest.java

@@ -71,6 +71,25 @@ public class CustomTest {
         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 testQueryStyleDeepObjectExplodeTrueObject() 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"));
+
+        Assert.assertEquals("query_object[id]=12345&query_object[name]=Hello%20World&query_object[category][id]=987&query_object[category][name]=new%20category&query_object[photoUrls][0]=http%3A%2F%2Fa.com&query_object[photoUrls][1]=http%3A%2F%2Fb.com", queryObject.toUrlQueryString("query_object"));
+
+        String response = api.testQueryStyleDeepObjectExplodeTrueObject(queryObject);
+        org.openapitools.client.EchoServerResponseParser p = new org.openapitools.client.EchoServerResponseParser(response);
+        Assert.assertEquals("/query/style_deepObject/explode_true/object?query_object[id]=12345&query_object[name]=Hello%20World&query_object[category][id]=987&query_object[category][name]=new%20category&query_object[photoUrls][0]=http%3A%2F%2Fa.com&query_object[photoUrls][1]=http%3A%2F%2Fb.com", p.path);
+    }
+
     /**
      * Test query parameter(s)
      * <p>
@@ -87,5 +106,4 @@ public class CustomTest {
         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);
     }
-
 }

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/api/FakeApi.java

@@ -241,11 +241,17 @@ public class FakeApi {
     String localVarPath = "/fake/http-signature-test";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "query_1";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("query_1", query1));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));
@@ -977,11 +983,17 @@ public class FakeApi {
     String localVarPath = "/fake/body-with-query-params";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "query";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("query", query));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));
@@ -1294,15 +1306,25 @@ public class FakeApi {
     String localVarPath = "/fake";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "enum_query_string_array";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("multi", "enum_query_string_array", enumQueryStringArray));
+    localVarQueryParameterBaseName = "enum_query_string";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("enum_query_string", enumQueryString));
+    localVarQueryParameterBaseName = "enum_query_integer";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("enum_query_integer", enumQueryInteger));
+    localVarQueryParameterBaseName = "enum_query_double";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("enum_query_double", enumQueryDouble));
+    localVarQueryParameterBaseName = "enum_query_model_array";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("multi", "enum_query_model_array", enumQueryModelArray));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));
@@ -1442,14 +1464,23 @@ public class FakeApi {
     String localVarPath = "/fake";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "required_string_group";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("required_string_group", requiredStringGroup));
+    localVarQueryParameterBaseName = "required_int64_group";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("required_int64_group", requiredInt64Group));
+    localVarQueryParameterBaseName = "string_group";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("string_group", stringGroup));
+    localVarQueryParameterBaseName = "int64_group";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("int64_group", int64Group));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));
@@ -1812,17 +1843,29 @@ public class FakeApi {
     String localVarPath = "/fake/test-query-parameters";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "pipe";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("pipes", "pipe", pipe));
+    localVarQueryParameterBaseName = "ioutil";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("csv", "ioutil", ioutil));
+    localVarQueryParameterBaseName = "http";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("ssv", "http", http));
+    localVarQueryParameterBaseName = "url";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("csv", "url", url));
+    localVarQueryParameterBaseName = "context";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("multi", "context", context));
+    localVarQueryParameterBaseName = "language";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("language", language));
+    localVarQueryParameterBaseName = "allowEmpty";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("allowEmpty", allowEmpty));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/api/PetApi.java

@@ -324,11 +324,17 @@ public class PetApi {
     String localVarPath = "/pet/findByStatus";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "status";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("csv", "status", status));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));
@@ -429,11 +435,17 @@ public class PetApi {
     String localVarPath = "/pet/findByTags";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "tags";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("csv", "tags", tags));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/api/UserApi.java

@@ -582,12 +582,19 @@ public class UserApi {
     String localVarPath = "/user/login";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "username";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("username", username));
+    localVarQueryParameterBaseName = "password";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("password", password));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/AdditionalPropertiesClass.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -153,5 +156,35 @@ public class AdditionalPropertiesClass {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `map_property` to the URL query string
+    if (getMapProperty() != null) {
+      for (String _key : getMapProperty().keySet()) {
+        joiner.add(String.format("%s[map_property][%s]=%s", prefix, getMapProperty().get(_key), URLEncoder.encode(String.valueOf(getMapProperty().get(_key)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    // add `map_of_map_property` to the URL query string
+    if (getMapOfMapProperty() != null) {
+      for (String _key : getMapOfMapProperty().keySet()) {
+        joiner.add(String.format("%s[map_of_map_property][%s]=%s", prefix, getMapOfMapProperty().get(_key), URLEncoder.encode(String.valueOf(getMapOfMapProperty().get(_key)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/AllOfWithSingleRef.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -136,5 +139,31 @@ public class AllOfWithSingleRef {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `username` to the URL query string
+    if (getUsername() != null) {
+      joiner.add(String.format("%s[username]=%s", prefix, URLEncoder.encode(String.valueOf(getUsername()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `SingleRefType` to the URL query string
+    if (getSingleRefType() != null) {
+      joiner.add(getSingleRefType().toUrlQueryString(prefix + "[SingleRefType]"));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/Animal.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
@@ -151,6 +154,32 @@ public class Animal {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `className` to the URL query string
+    if (getClassName() != null) {
+      joiner.add(String.format("%s[className]=%s", prefix, URLEncoder.encode(String.valueOf(getClassName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `color` to the URL query string
+    if (getColor() != null) {
+      joiner.add(String.format("%s[color]=%s", prefix, URLEncoder.encode(String.valueOf(getColor()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 static {
   // Initialize and register the discriminator mappings.
   Map<String, Class<?>> mappings = new HashMap<String, Class<?>>();

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/ArrayOfArrayOfNumberOnly.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -115,5 +118,30 @@ public class ArrayOfArrayOfNumberOnly {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `ArrayArrayNumber` to the URL query string
+    if (getArrayArrayNumber() != null) {
+      for (int i = 0; i < getArrayArrayNumber().size(); i++) {
+        if (getArrayArrayNumber().get(i) != null) {
+          joiner.add(String.format("%s[ArrayArrayNumber][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getArrayArrayNumber().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+        }
+      }
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/ArrayOfNumberOnly.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -115,5 +118,30 @@ public class ArrayOfNumberOnly {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `ArrayNumber` to the URL query string
+    if (getArrayNumber() != null) {
+      for (int i = 0; i < getArrayNumber().size(); i++) {
+        if (getArrayNumber().get(i) != null) {
+          joiner.add(String.format("%s[ArrayNumber][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getArrayNumber().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+        }
+      }
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/ArrayTest.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -193,5 +196,44 @@ public class ArrayTest {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `array_of_string` to the URL query string
+    if (getArrayOfString() != null) {
+      for (int i = 0; i < getArrayOfString().size(); i++) {
+        joiner.add(String.format("%s[array_of_string][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getArrayOfString().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    // add `array_array_of_integer` to the URL query string
+    if (getArrayArrayOfInteger() != null) {
+      for (int i = 0; i < getArrayArrayOfInteger().size(); i++) {
+        joiner.add(String.format("%s[array_array_of_integer][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getArrayArrayOfInteger().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    // add `array_array_of_model` to the URL query string
+    if (getArrayArrayOfModel() != null) {
+      for (int i = 0; i < getArrayArrayOfModel().size(); i++) {
+        if (getArrayArrayOfModel().get(i) != null) {
+          joiner.add(String.format("%s[array_array_of_model][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getArrayArrayOfModel().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+        }
+      }
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/Capitalization.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -259,5 +262,51 @@ public class Capitalization {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `smallCamel` to the URL query string
+    if (getSmallCamel() != null) {
+      joiner.add(String.format("%s[smallCamel]=%s", prefix, URLEncoder.encode(String.valueOf(getSmallCamel()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `CapitalCamel` to the URL query string
+    if (getCapitalCamel() != null) {
+      joiner.add(String.format("%s[CapitalCamel]=%s", prefix, URLEncoder.encode(String.valueOf(getCapitalCamel()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `small_Snake` to the URL query string
+    if (getSmallSnake() != null) {
+      joiner.add(String.format("%s[small_Snake]=%s", prefix, URLEncoder.encode(String.valueOf(getSmallSnake()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `Capital_Snake` to the URL query string
+    if (getCapitalSnake() != null) {
+      joiner.add(String.format("%s[Capital_Snake]=%s", prefix, URLEncoder.encode(String.valueOf(getCapitalSnake()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `SCA_ETH_Flow_Points` to the URL query string
+    if (getScAETHFlowPoints() != null) {
+      joiner.add(String.format("%s[SCA_ETH_Flow_Points]=%s", prefix, URLEncoder.encode(String.valueOf(getScAETHFlowPoints()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `ATT_NAME` to the URL query string
+    if (getATTNAME() != null) {
+      joiner.add(String.format("%s[ATT_NAME]=%s", prefix, URLEncoder.encode(String.valueOf(getATTNAME()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/Cat.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
@@ -117,6 +120,37 @@ public class Cat extends Animal {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `className` to the URL query string
+    if (getClassName() != null) {
+      joiner.add(String.format("%s[className]=%s", prefix, URLEncoder.encode(String.valueOf(getClassName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `color` to the URL query string
+    if (getColor() != null) {
+      joiner.add(String.format("%s[color]=%s", prefix, URLEncoder.encode(String.valueOf(getColor()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `declawed` to the URL query string
+    if (getDeclawed() != null) {
+      joiner.add(String.format("%s[declawed]=%s", prefix, URLEncoder.encode(String.valueOf(getDeclawed()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 static {
   // Initialize and register the discriminator mappings.
   Map<String, Class<?>> mappings = new HashMap<String, Class<?>>();

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/CatAllOf.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -104,5 +107,26 @@ public class CatAllOf {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `declawed` to the URL query string
+    if (getDeclawed() != null) {
+      joiner.add(String.format("%s[declawed]=%s", prefix, URLEncoder.encode(String.valueOf(getDeclawed()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/Category.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -135,5 +138,31 @@ public class Category {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `id` to the URL query string
+    if (getId() != null) {
+      joiner.add(String.format("%s[id]=%s", prefix, URLEncoder.encode(String.valueOf(getId()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `name` to the URL query string
+    if (getName() != null) {
+      joiner.add(String.format("%s[name]=%s", prefix, URLEncoder.encode(String.valueOf(getName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/ClassModel.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -104,5 +107,26 @@ public class ClassModel {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `_class` to the URL query string
+    if (getPropertyClass() != null) {
+      joiner.add(String.format("%s[_class]=%s", prefix, URLEncoder.encode(String.valueOf(getPropertyClass()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/Client.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -104,5 +107,26 @@ public class Client {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `client` to the URL query string
+    if (getClient() != null) {
+      joiner.add(String.format("%s[client]=%s", prefix, URLEncoder.encode(String.valueOf(getClient()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/DeprecatedObject.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -106,5 +109,26 @@ public class DeprecatedObject {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `name` to the URL query string
+    if (getName() != null) {
+      joiner.add(String.format("%s[name]=%s", prefix, URLEncoder.encode(String.valueOf(getName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/Dog.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
@@ -117,6 +120,37 @@ public class Dog extends Animal {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `className` to the URL query string
+    if (getClassName() != null) {
+      joiner.add(String.format("%s[className]=%s", prefix, URLEncoder.encode(String.valueOf(getClassName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `color` to the URL query string
+    if (getColor() != null) {
+      joiner.add(String.format("%s[color]=%s", prefix, URLEncoder.encode(String.valueOf(getColor()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `breed` to the URL query string
+    if (getBreed() != null) {
+      joiner.add(String.format("%s[breed]=%s", prefix, URLEncoder.encode(String.valueOf(getBreed()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 static {
   // Initialize and register the discriminator mappings.
   Map<String, Class<?>> mappings = new HashMap<String, Class<?>>();

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/DogAllOf.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -104,5 +107,26 @@ public class DogAllOf {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `breed` to the URL query string
+    if (getBreed() != null) {
+      joiner.add(String.format("%s[breed]=%s", prefix, URLEncoder.encode(String.valueOf(getBreed()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/EnumArrays.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -215,5 +218,33 @@ public class EnumArrays {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `just_symbol` to the URL query string
+    if (getJustSymbol() != null) {
+      joiner.add(String.format("%s[just_symbol]=%s", prefix, URLEncoder.encode(String.valueOf(getJustSymbol()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `array_enum` to the URL query string
+    if (getArrayEnum() != null) {
+      for (int i = 0; i < getArrayEnum().size(); i++) {
+        joiner.add(String.format("%s[array_enum][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getArrayEnum().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/EnumClass.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 
@@ -59,5 +62,20 @@ public enum EnumClass {
     }
     throw new IllegalArgumentException("Unexpected value '" + value + "'");
   }
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    return String.format("%s=%s", prefix, this.toString());
+  }
+
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/EnumTest.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -492,5 +495,61 @@ public class EnumTest {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `enum_string` to the URL query string
+    if (getEnumString() != null) {
+      joiner.add(String.format("%s[enum_string]=%s", prefix, URLEncoder.encode(String.valueOf(getEnumString()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `enum_string_required` to the URL query string
+    if (getEnumStringRequired() != null) {
+      joiner.add(String.format("%s[enum_string_required]=%s", prefix, URLEncoder.encode(String.valueOf(getEnumStringRequired()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `enum_integer` to the URL query string
+    if (getEnumInteger() != null) {
+      joiner.add(String.format("%s[enum_integer]=%s", prefix, URLEncoder.encode(String.valueOf(getEnumInteger()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `enum_number` to the URL query string
+    if (getEnumNumber() != null) {
+      joiner.add(String.format("%s[enum_number]=%s", prefix, URLEncoder.encode(String.valueOf(getEnumNumber()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `outerEnum` to the URL query string
+    if (getOuterEnum() != null) {
+      joiner.add(String.format("%s[outerEnum]=%s", prefix, URLEncoder.encode(String.valueOf(getOuterEnum()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `outerEnumInteger` to the URL query string
+    if (getOuterEnumInteger() != null) {
+      joiner.add(String.format("%s[outerEnumInteger]=%s", prefix, URLEncoder.encode(String.valueOf(getOuterEnumInteger()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `outerEnumDefaultValue` to the URL query string
+    if (getOuterEnumDefaultValue() != null) {
+      joiner.add(String.format("%s[outerEnumDefaultValue]=%s", prefix, URLEncoder.encode(String.valueOf(getOuterEnumDefaultValue()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `outerEnumIntegerDefaultValue` to the URL query string
+    if (getOuterEnumIntegerDefaultValue() != null) {
+      joiner.add(String.format("%s[outerEnumIntegerDefaultValue]=%s", prefix, URLEncoder.encode(String.valueOf(getOuterEnumIntegerDefaultValue()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/FileSchemaTestClass.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -146,5 +149,35 @@ public class FileSchemaTestClass {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `file` to the URL query string
+    if (getFile() != null) {
+      joiner.add(getFile().toUrlQueryString(prefix + "[file]"));
+    }
+
+    // add `files` to the URL query string
+    if (getFiles() != null) {
+      for (int i = 0; i < getFiles().size(); i++) {
+        if (getFiles().get(i) != null) {
+          joiner.add(getFiles().get(i).toUrlQueryString(String.format("%s[files][%d]", prefix, i)));
+        }
+      }
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/Foo.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -104,5 +107,26 @@ public class Foo {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `bar` to the URL query string
+    if (getBar() != null) {
+      joiner.add(String.format("%s[bar]=%s", prefix, URLEncoder.encode(String.valueOf(getBar()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/FooGetDefaultResponse.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -105,5 +108,26 @@ public class FooGetDefaultResponse {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `string` to the URL query string
+    if (getString() != null) {
+      joiner.add(getString().toUrlQueryString(prefix + "[string]"));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/FormatTest.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -584,5 +587,101 @@ public class FormatTest {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `integer` to the URL query string
+    if (getInteger() != null) {
+      joiner.add(String.format("%s[integer]=%s", prefix, URLEncoder.encode(String.valueOf(getInteger()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `int32` to the URL query string
+    if (getInt32() != null) {
+      joiner.add(String.format("%s[int32]=%s", prefix, URLEncoder.encode(String.valueOf(getInt32()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `int64` to the URL query string
+    if (getInt64() != null) {
+      joiner.add(String.format("%s[int64]=%s", prefix, URLEncoder.encode(String.valueOf(getInt64()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `number` to the URL query string
+    if (getNumber() != null) {
+      joiner.add(String.format("%s[number]=%s", prefix, URLEncoder.encode(String.valueOf(getNumber()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `float` to the URL query string
+    if (getFloat() != null) {
+      joiner.add(String.format("%s[float]=%s", prefix, URLEncoder.encode(String.valueOf(getFloat()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `double` to the URL query string
+    if (getDouble() != null) {
+      joiner.add(String.format("%s[double]=%s", prefix, URLEncoder.encode(String.valueOf(getDouble()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `decimal` to the URL query string
+    if (getDecimal() != null) {
+      joiner.add(String.format("%s[decimal]=%s", prefix, URLEncoder.encode(String.valueOf(getDecimal()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `string` to the URL query string
+    if (getString() != null) {
+      joiner.add(String.format("%s[string]=%s", prefix, URLEncoder.encode(String.valueOf(getString()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `byte` to the URL query string
+    if (getByte() != null) {
+      joiner.add(String.format("%s[byte]=%s", prefix, URLEncoder.encode(String.valueOf(getByte()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `binary` to the URL query string
+    if (getBinary() != null) {
+      joiner.add(String.format("%s[binary]=%s", prefix, URLEncoder.encode(String.valueOf(getBinary()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `date` to the URL query string
+    if (getDate() != null) {
+      joiner.add(String.format("%s[date]=%s", prefix, URLEncoder.encode(String.valueOf(getDate()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `dateTime` to the URL query string
+    if (getDateTime() != null) {
+      joiner.add(String.format("%s[dateTime]=%s", prefix, URLEncoder.encode(String.valueOf(getDateTime()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `uuid` to the URL query string
+    if (getUuid() != null) {
+      joiner.add(String.format("%s[uuid]=%s", prefix, URLEncoder.encode(String.valueOf(getUuid()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `password` to the URL query string
+    if (getPassword() != null) {
+      joiner.add(String.format("%s[password]=%s", prefix, URLEncoder.encode(String.valueOf(getPassword()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `pattern_with_digits` to the URL query string
+    if (getPatternWithDigits() != null) {
+      joiner.add(String.format("%s[pattern_with_digits]=%s", prefix, URLEncoder.encode(String.valueOf(getPatternWithDigits()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `pattern_with_digits_and_delimiter` to the URL query string
+    if (getPatternWithDigitsAndDelimiter() != null) {
+      joiner.add(String.format("%s[pattern_with_digits_and_delimiter]=%s", prefix, URLEncoder.encode(String.valueOf(getPatternWithDigitsAndDelimiter()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/HasOnlyReadOnly.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -125,5 +128,31 @@ public class HasOnlyReadOnly {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `bar` to the URL query string
+    if (getBar() != null) {
+      joiner.add(String.format("%s[bar]=%s", prefix, URLEncoder.encode(String.valueOf(getBar()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `foo` to the URL query string
+    if (getFoo() != null) {
+      joiner.add(String.format("%s[foo]=%s", prefix, URLEncoder.encode(String.valueOf(getFoo()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/HealthCheckResult.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -127,5 +130,26 @@ public class HealthCheckResult {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `NullableMessage` to the URL query string
+    if (getNullableMessage() != null) {
+      joiner.add(String.format("%s[NullableMessage]=%s", prefix, URLEncoder.encode(String.valueOf(getNullableMessage()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/MapTest.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -266,5 +269,49 @@ public class MapTest {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `map_map_of_string` to the URL query string
+    if (getMapMapOfString() != null) {
+      for (String _key : getMapMapOfString().keySet()) {
+        joiner.add(String.format("%s[map_map_of_string][%s]=%s", prefix, getMapMapOfString().get(_key), URLEncoder.encode(String.valueOf(getMapMapOfString().get(_key)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    // add `map_of_enum_string` to the URL query string
+    if (getMapOfEnumString() != null) {
+      for (String _key : getMapOfEnumString().keySet()) {
+        joiner.add(String.format("%s[map_of_enum_string][%s]=%s", prefix, getMapOfEnumString().get(_key), URLEncoder.encode(String.valueOf(getMapOfEnumString().get(_key)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    // add `direct_map` to the URL query string
+    if (getDirectMap() != null) {
+      for (String _key : getDirectMap().keySet()) {
+        joiner.add(String.format("%s[direct_map][%s]=%s", prefix, getDirectMap().get(_key), URLEncoder.encode(String.valueOf(getDirectMap().get(_key)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    // add `indirect_map` to the URL query string
+    if (getIndirectMap() != null) {
+      for (String _key : getIndirectMap().keySet()) {
+        joiner.add(String.format("%s[indirect_map][%s]=%s", prefix, getIndirectMap().get(_key), URLEncoder.encode(String.valueOf(getIndirectMap().get(_key)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/MixedPropertiesAndAdditionalPropertiesClass.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -179,5 +182,40 @@ public class MixedPropertiesAndAdditionalPropertiesClass {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `uuid` to the URL query string
+    if (getUuid() != null) {
+      joiner.add(String.format("%s[uuid]=%s", prefix, URLEncoder.encode(String.valueOf(getUuid()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `dateTime` to the URL query string
+    if (getDateTime() != null) {
+      joiner.add(String.format("%s[dateTime]=%s", prefix, URLEncoder.encode(String.valueOf(getDateTime()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `map` to the URL query string
+    if (getMap() != null) {
+      for (String _key : getMap().keySet()) {
+        if (getMap().get(_key) != null) {
+          joiner.add(getMap().get(_key).toUrlQueryString(String.format("%s[map][%s]", prefix, _key)));
+        }
+      }
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/Model200Response.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -135,5 +138,31 @@ public class Model200Response {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `name` to the URL query string
+    if (getName() != null) {
+      joiner.add(String.format("%s[name]=%s", prefix, URLEncoder.encode(String.valueOf(getName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `class` to the URL query string
+    if (getPropertyClass() != null) {
+      joiner.add(String.format("%s[class]=%s", prefix, URLEncoder.encode(String.valueOf(getPropertyClass()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/ModelApiResponse.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -166,5 +169,36 @@ public class ModelApiResponse {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `code` to the URL query string
+    if (getCode() != null) {
+      joiner.add(String.format("%s[code]=%s", prefix, URLEncoder.encode(String.valueOf(getCode()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `type` to the URL query string
+    if (getType() != null) {
+      joiner.add(String.format("%s[type]=%s", prefix, URLEncoder.encode(String.valueOf(getType()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `message` to the URL query string
+    if (getMessage() != null) {
+      joiner.add(String.format("%s[message]=%s", prefix, URLEncoder.encode(String.valueOf(getMessage()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/ModelFile.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -104,5 +107,26 @@ public class ModelFile {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `sourceURI` to the URL query string
+    if (getSourceURI() != null) {
+      joiner.add(String.format("%s[sourceURI]=%s", prefix, URLEncoder.encode(String.valueOf(getSourceURI()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/ModelList.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -104,5 +107,26 @@ public class ModelList {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `123-list` to the URL query string
+    if (get123list() != null) {
+      joiner.add(String.format("%s[123-list]=%s", prefix, URLEncoder.encode(String.valueOf(get123list()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/ModelReturn.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -104,5 +107,26 @@ public class ModelReturn {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `return` to the URL query string
+    if (getReturn() != null) {
+      joiner.add(String.format("%s[return]=%s", prefix, URLEncoder.encode(String.valueOf(getReturn()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/Name.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -187,5 +190,41 @@ public class Name {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `name` to the URL query string
+    if (getName() != null) {
+      joiner.add(String.format("%s[name]=%s", prefix, URLEncoder.encode(String.valueOf(getName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `snake_case` to the URL query string
+    if (getSnakeCase() != null) {
+      joiner.add(String.format("%s[snake_case]=%s", prefix, URLEncoder.encode(String.valueOf(getSnakeCase()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `property` to the URL query string
+    if (getProperty() != null) {
+      joiner.add(String.format("%s[property]=%s", prefix, URLEncoder.encode(String.valueOf(getProperty()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `123Number` to the URL query string
+    if (get123number() != null) {
+      joiner.add(String.format("%s[123Number]=%s", prefix, URLEncoder.encode(String.valueOf(get123number()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/NullableClass.java

@@ -17,10 +17,13 @@ import java.util.Map;
 import java.util.HashMap;
 import com.fasterxml.jackson.annotation.JsonAnyGetter;
 import com.fasterxml.jackson.annotation.JsonAnySetter;
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -662,5 +665,93 @@ public class NullableClass extends HashMap<String, Object> {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `integer_prop` to the URL query string
+    if (getIntegerProp() != null) {
+      joiner.add(String.format("%s[integer_prop]=%s", prefix, URLEncoder.encode(String.valueOf(getIntegerProp()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `number_prop` to the URL query string
+    if (getNumberProp() != null) {
+      joiner.add(String.format("%s[number_prop]=%s", prefix, URLEncoder.encode(String.valueOf(getNumberProp()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `boolean_prop` to the URL query string
+    if (getBooleanProp() != null) {
+      joiner.add(String.format("%s[boolean_prop]=%s", prefix, URLEncoder.encode(String.valueOf(getBooleanProp()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `string_prop` to the URL query string
+    if (getStringProp() != null) {
+      joiner.add(String.format("%s[string_prop]=%s", prefix, URLEncoder.encode(String.valueOf(getStringProp()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `date_prop` to the URL query string
+    if (getDateProp() != null) {
+      joiner.add(String.format("%s[date_prop]=%s", prefix, URLEncoder.encode(String.valueOf(getDateProp()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `datetime_prop` to the URL query string
+    if (getDatetimeProp() != null) {
+      joiner.add(String.format("%s[datetime_prop]=%s", prefix, URLEncoder.encode(String.valueOf(getDatetimeProp()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `array_nullable_prop` to the URL query string
+    if (getArrayNullableProp() != null) {
+      for (int i = 0; i < getArrayNullableProp().size(); i++) {
+        joiner.add(String.format("%s[array_nullable_prop][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getArrayNullableProp().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    // add `array_and_items_nullable_prop` to the URL query string
+    if (getArrayAndItemsNullableProp() != null) {
+      for (int i = 0; i < getArrayAndItemsNullableProp().size(); i++) {
+        joiner.add(String.format("%s[array_and_items_nullable_prop][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getArrayAndItemsNullableProp().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    // add `array_items_nullable` to the URL query string
+    if (getArrayItemsNullable() != null) {
+      for (int i = 0; i < getArrayItemsNullable().size(); i++) {
+        joiner.add(String.format("%s[array_items_nullable][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getArrayItemsNullable().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    // add `object_nullable_prop` to the URL query string
+    if (getObjectNullableProp() != null) {
+      for (String _key : getObjectNullableProp().keySet()) {
+        joiner.add(String.format("%s[object_nullable_prop][%s]=%s", prefix, getObjectNullableProp().get(_key), URLEncoder.encode(String.valueOf(getObjectNullableProp().get(_key)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    // add `object_and_items_nullable_prop` to the URL query string
+    if (getObjectAndItemsNullableProp() != null) {
+      for (String _key : getObjectAndItemsNullableProp().keySet()) {
+        joiner.add(String.format("%s[object_and_items_nullable_prop][%s]=%s", prefix, getObjectAndItemsNullableProp().get(_key), URLEncoder.encode(String.valueOf(getObjectAndItemsNullableProp().get(_key)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    // add `object_items_nullable` to the URL query string
+    if (getObjectItemsNullable() != null) {
+      for (String _key : getObjectItemsNullable().keySet()) {
+        joiner.add(String.format("%s[object_items_nullable][%s]=%s", prefix, getObjectItemsNullable().get(_key), URLEncoder.encode(String.valueOf(getObjectItemsNullable().get(_key)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/NumberOnly.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -105,5 +108,26 @@ public class NumberOnly {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `JustNumber` to the URL query string
+    if (getJustNumber() != null) {
+      joiner.add(String.format("%s[JustNumber]=%s", prefix, URLEncoder.encode(String.valueOf(getJustNumber()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/ObjectWithDeprecatedFields.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -215,5 +218,43 @@ public class ObjectWithDeprecatedFields {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `uuid` to the URL query string
+    if (getUuid() != null) {
+      joiner.add(String.format("%s[uuid]=%s", prefix, URLEncoder.encode(String.valueOf(getUuid()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `id` to the URL query string
+    if (getId() != null) {
+      joiner.add(String.format("%s[id]=%s", prefix, URLEncoder.encode(String.valueOf(getId()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `deprecatedRef` to the URL query string
+    if (getDeprecatedRef() != null) {
+      joiner.add(getDeprecatedRef().toUrlQueryString(prefix + "[deprecatedRef]"));
+    }
+
+    // add `bars` to the URL query string
+    if (getBars() != null) {
+      for (int i = 0; i < getBars().size(); i++) {
+        joiner.add(String.format("%s[bars][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getBars().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/Order.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -297,5 +300,51 @@ public class Order {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `id` to the URL query string
+    if (getId() != null) {
+      joiner.add(String.format("%s[id]=%s", prefix, URLEncoder.encode(String.valueOf(getId()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `petId` to the URL query string
+    if (getPetId() != null) {
+      joiner.add(String.format("%s[petId]=%s", prefix, URLEncoder.encode(String.valueOf(getPetId()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `quantity` to the URL query string
+    if (getQuantity() != null) {
+      joiner.add(String.format("%s[quantity]=%s", prefix, URLEncoder.encode(String.valueOf(getQuantity()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `shipDate` to the URL query string
+    if (getShipDate() != null) {
+      joiner.add(String.format("%s[shipDate]=%s", prefix, URLEncoder.encode(String.valueOf(getShipDate()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `status` to the URL query string
+    if (getStatus() != null) {
+      joiner.add(String.format("%s[status]=%s", prefix, URLEncoder.encode(String.valueOf(getStatus()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `complete` to the URL query string
+    if (getComplete() != null) {
+      joiner.add(String.format("%s[complete]=%s", prefix, URLEncoder.encode(String.valueOf(getComplete()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/OuterComposite.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -167,5 +170,36 @@ public class OuterComposite {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `my_number` to the URL query string
+    if (getMyNumber() != null) {
+      joiner.add(String.format("%s[my_number]=%s", prefix, URLEncoder.encode(String.valueOf(getMyNumber()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `my_string` to the URL query string
+    if (getMyString() != null) {
+      joiner.add(String.format("%s[my_string]=%s", prefix, URLEncoder.encode(String.valueOf(getMyString()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `my_boolean` to the URL query string
+    if (getMyBoolean() != null) {
+      joiner.add(String.format("%s[my_boolean]=%s", prefix, URLEncoder.encode(String.valueOf(getMyBoolean()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/OuterEnum.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 
@@ -59,5 +62,20 @@ public enum OuterEnum {
     }
     return null;
   }
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    return String.format("%s=%s", prefix, this.toString());
+  }
+
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/OuterEnumDefaultValue.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 
@@ -59,5 +62,20 @@ public enum OuterEnumDefaultValue {
     }
     throw new IllegalArgumentException("Unexpected value '" + value + "'");
   }
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    return String.format("%s=%s", prefix, this.toString());
+  }
+
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/OuterEnumInteger.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 
@@ -59,5 +62,20 @@ public enum OuterEnumInteger {
     }
     throw new IllegalArgumentException("Unexpected value '" + value + "'");
   }
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    return String.format("%s=%s", prefix, this.toString());
+  }
+
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/OuterEnumIntegerDefaultValue.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 
@@ -59,5 +62,20 @@ public enum OuterEnumIntegerDefaultValue {
     }
     throw new IllegalArgumentException("Unexpected value '" + value + "'");
   }
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    return String.format("%s=%s", prefix, this.toString());
+  }
+
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/OuterObjectWithEnumProperty.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -105,5 +108,26 @@ public class OuterObjectWithEnumProperty {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `value` to the URL query string
+    if (getValue() != null) {
+      joiner.add(String.format("%s[value]=%s", prefix, URLEncoder.encode(String.valueOf(getValue()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/Pet.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -317,5 +320,59 @@ public class Pet {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `id` to the URL query string
+    if (getId() != null) {
+      joiner.add(String.format("%s[id]=%s", prefix, URLEncoder.encode(String.valueOf(getId()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `category` to the URL query string
+    if (getCategory() != null) {
+      joiner.add(getCategory().toUrlQueryString(prefix + "[category]"));
+    }
+
+    // add `name` to the URL query string
+    if (getName() != null) {
+      joiner.add(String.format("%s[name]=%s", prefix, URLEncoder.encode(String.valueOf(getName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `photoUrls` to the URL query string
+    if (getPhotoUrls() != null) {
+      int i = 0;
+      for (String _item : getPhotoUrls()) {
+        joiner.add(String.format("%s[photoUrls][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(_item), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+      i++;
+    }
+
+    // add `tags` to the URL query string
+    if (getTags() != null) {
+      for (int i = 0; i < getTags().size(); i++) {
+        if (getTags().get(i) != null) {
+          joiner.add(getTags().get(i).toUrlQueryString(String.format("%s[tags][%d]", prefix, i)));
+        }
+      }
+    }
+
+    // add `status` to the URL query string
+    if (getStatus() != null) {
+      joiner.add(String.format("%s[status]=%s", prefix, URLEncoder.encode(String.valueOf(getStatus()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/ReadOnlyFirst.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -133,5 +136,31 @@ public class ReadOnlyFirst {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `bar` to the URL query string
+    if (getBar() != null) {
+      joiner.add(String.format("%s[bar]=%s", prefix, URLEncoder.encode(String.valueOf(getBar()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `baz` to the URL query string
+    if (getBaz() != null) {
+      joiner.add(String.format("%s[baz]=%s", prefix, URLEncoder.encode(String.valueOf(getBaz()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/SingleRefType.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 
@@ -57,5 +60,20 @@ public enum SingleRefType {
     }
     throw new IllegalArgumentException("Unexpected value '" + value + "'");
   }
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    return String.format("%s=%s", prefix, this.toString());
+  }
+
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/SpecialModelName.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -104,5 +107,26 @@ public class SpecialModelName {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `$special[property.name]` to the URL query string
+    if (get$SpecialPropertyName() != null) {
+      joiner.add(String.format("%s[$special[property.name]]=%s", prefix, URLEncoder.encode(String.valueOf(get$SpecialPropertyName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/Tag.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -135,5 +138,31 @@ public class Tag {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `id` to the URL query string
+    if (getId() != null) {
+      joiner.add(String.format("%s[id]=%s", prefix, URLEncoder.encode(String.valueOf(getId()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `name` to the URL query string
+    if (getName() != null) {
+      joiner.add(String.format("%s[name]=%s", prefix, URLEncoder.encode(String.valueOf(getName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/model/User.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -321,5 +324,61 @@ public class User {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `id` to the URL query string
+    if (getId() != null) {
+      joiner.add(String.format("%s[id]=%s", prefix, URLEncoder.encode(String.valueOf(getId()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `username` to the URL query string
+    if (getUsername() != null) {
+      joiner.add(String.format("%s[username]=%s", prefix, URLEncoder.encode(String.valueOf(getUsername()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `firstName` to the URL query string
+    if (getFirstName() != null) {
+      joiner.add(String.format("%s[firstName]=%s", prefix, URLEncoder.encode(String.valueOf(getFirstName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `lastName` to the URL query string
+    if (getLastName() != null) {
+      joiner.add(String.format("%s[lastName]=%s", prefix, URLEncoder.encode(String.valueOf(getLastName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `email` to the URL query string
+    if (getEmail() != null) {
+      joiner.add(String.format("%s[email]=%s", prefix, URLEncoder.encode(String.valueOf(getEmail()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `password` to the URL query string
+    if (getPassword() != null) {
+      joiner.add(String.format("%s[password]=%s", prefix, URLEncoder.encode(String.valueOf(getPassword()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `phone` to the URL query string
+    if (getPhone() != null) {
+      joiner.add(String.format("%s[phone]=%s", prefix, URLEncoder.encode(String.valueOf(getPhone()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `userStatus` to the URL query string
+    if (getUserStatus() != null) {
+      joiner.add(String.format("%s[userStatus]=%s", prefix, URLEncoder.encode(String.valueOf(getUserStatus()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-jakarta/src/main/java/org/openapitools/client/api/PetApi.java

@@ -292,11 +292,17 @@ public class PetApi {
     String localVarPath = "/pet/findByStatus";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "status";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("csv", "status", status));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));
@@ -376,11 +382,17 @@ public class PetApi {
     String localVarPath = "/pet/findByTags";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "tags";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("csv", "tags", tags));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));

samples/client/petstore/java/native-jakarta/src/main/java/org/openapitools/client/api/UserApi.java

@@ -527,12 +527,19 @@ public class UserApi {
     String localVarPath = "/user/login";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "username";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("username", username));
+    localVarQueryParameterBaseName = "password";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("password", password));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));

samples/client/petstore/java/native-jakarta/src/main/java/org/openapitools/client/model/Category.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -135,5 +138,31 @@ public class Category {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `id` to the URL query string
+    if (getId() != null) {
+      joiner.add(String.format("%s[id]=%s", prefix, URLEncoder.encode(String.valueOf(getId()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `name` to the URL query string
+    if (getName() != null) {
+      joiner.add(String.format("%s[name]=%s", prefix, URLEncoder.encode(String.valueOf(getName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-jakarta/src/main/java/org/openapitools/client/model/ModelApiResponse.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -166,5 +169,36 @@ public class ModelApiResponse {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `code` to the URL query string
+    if (getCode() != null) {
+      joiner.add(String.format("%s[code]=%s", prefix, URLEncoder.encode(String.valueOf(getCode()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `type` to the URL query string
+    if (getType() != null) {
+      joiner.add(String.format("%s[type]=%s", prefix, URLEncoder.encode(String.valueOf(getType()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `message` to the URL query string
+    if (getMessage() != null) {
+      joiner.add(String.format("%s[message]=%s", prefix, URLEncoder.encode(String.valueOf(getMessage()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-jakarta/src/main/java/org/openapitools/client/model/Order.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -297,5 +300,51 @@ public class Order {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `id` to the URL query string
+    if (getId() != null) {
+      joiner.add(String.format("%s[id]=%s", prefix, URLEncoder.encode(String.valueOf(getId()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `petId` to the URL query string
+    if (getPetId() != null) {
+      joiner.add(String.format("%s[petId]=%s", prefix, URLEncoder.encode(String.valueOf(getPetId()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `quantity` to the URL query string
+    if (getQuantity() != null) {
+      joiner.add(String.format("%s[quantity]=%s", prefix, URLEncoder.encode(String.valueOf(getQuantity()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `shipDate` to the URL query string
+    if (getShipDate() != null) {
+      joiner.add(String.format("%s[shipDate]=%s", prefix, URLEncoder.encode(String.valueOf(getShipDate()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `status` to the URL query string
+    if (getStatus() != null) {
+      joiner.add(String.format("%s[status]=%s", prefix, URLEncoder.encode(String.valueOf(getStatus()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `complete` to the URL query string
+    if (getComplete() != null) {
+      joiner.add(String.format("%s[complete]=%s", prefix, URLEncoder.encode(String.valueOf(getComplete()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-jakarta/src/main/java/org/openapitools/client/model/Pet.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -315,5 +318,57 @@ public class Pet {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `id` to the URL query string
+    if (getId() != null) {
+      joiner.add(String.format("%s[id]=%s", prefix, URLEncoder.encode(String.valueOf(getId()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `category` to the URL query string
+    if (getCategory() != null) {
+      joiner.add(getCategory().toUrlQueryString(prefix + "[category]"));
+    }
+
+    // add `name` to the URL query string
+    if (getName() != null) {
+      joiner.add(String.format("%s[name]=%s", prefix, URLEncoder.encode(String.valueOf(getName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `photoUrls` to the URL query string
+    if (getPhotoUrls() != null) {
+      for (int i = 0; i < getPhotoUrls().size(); i++) {
+        joiner.add(String.format("%s[photoUrls][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getPhotoUrls().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    // add `tags` to the URL query string
+    if (getTags() != null) {
+      for (int i = 0; i < getTags().size(); i++) {
+        if (getTags().get(i) != null) {
+          joiner.add(getTags().get(i).toUrlQueryString(String.format("%s[tags][%d]", prefix, i)));
+        }
+      }
+    }
+
+    // add `status` to the URL query string
+    if (getStatus() != null) {
+      joiner.add(String.format("%s[status]=%s", prefix, URLEncoder.encode(String.valueOf(getStatus()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-jakarta/src/main/java/org/openapitools/client/model/Tag.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -135,5 +138,31 @@ public class Tag {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `id` to the URL query string
+    if (getId() != null) {
+      joiner.add(String.format("%s[id]=%s", prefix, URLEncoder.encode(String.valueOf(getId()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `name` to the URL query string
+    if (getName() != null) {
+      joiner.add(String.format("%s[name]=%s", prefix, URLEncoder.encode(String.valueOf(getName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native-jakarta/src/main/java/org/openapitools/client/model/User.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -321,5 +324,61 @@ public class User {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `id` to the URL query string
+    if (getId() != null) {
+      joiner.add(String.format("%s[id]=%s", prefix, URLEncoder.encode(String.valueOf(getId()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `username` to the URL query string
+    if (getUsername() != null) {
+      joiner.add(String.format("%s[username]=%s", prefix, URLEncoder.encode(String.valueOf(getUsername()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `firstName` to the URL query string
+    if (getFirstName() != null) {
+      joiner.add(String.format("%s[firstName]=%s", prefix, URLEncoder.encode(String.valueOf(getFirstName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `lastName` to the URL query string
+    if (getLastName() != null) {
+      joiner.add(String.format("%s[lastName]=%s", prefix, URLEncoder.encode(String.valueOf(getLastName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `email` to the URL query string
+    if (getEmail() != null) {
+      joiner.add(String.format("%s[email]=%s", prefix, URLEncoder.encode(String.valueOf(getEmail()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `password` to the URL query string
+    if (getPassword() != null) {
+      joiner.add(String.format("%s[password]=%s", prefix, URLEncoder.encode(String.valueOf(getPassword()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `phone` to the URL query string
+    if (getPhone() != null) {
+      joiner.add(String.format("%s[phone]=%s", prefix, URLEncoder.encode(String.valueOf(getPhone()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `userStatus` to the URL query string
+    if (getUserStatus() != null) {
+      joiner.add(String.format("%s[userStatus]=%s", prefix, URLEncoder.encode(String.valueOf(getUserStatus()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native/src/main/java/org/openapitools/client/api/FakeApi.java

@@ -216,11 +216,17 @@ public class FakeApi {
     String localVarPath = "/fake/http-signature-test";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "query_1";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("query_1", query1));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));
@@ -838,11 +844,17 @@ public class FakeApi {
     String localVarPath = "/fake/body-with-query-params";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "query";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("query", query));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));
@@ -1128,15 +1140,25 @@ public class FakeApi {
     String localVarPath = "/fake";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "enum_query_string_array";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("multi", "enum_query_string_array", enumQueryStringArray));
+    localVarQueryParameterBaseName = "enum_query_string";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("enum_query_string", enumQueryString));
+    localVarQueryParameterBaseName = "enum_query_integer";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("enum_query_integer", enumQueryInteger));
+    localVarQueryParameterBaseName = "enum_query_double";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("enum_query_double", enumQueryDouble));
+    localVarQueryParameterBaseName = "enum_query_model_array";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("multi", "enum_query_model_array", enumQueryModelArray));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));
@@ -1272,14 +1294,23 @@ public class FakeApi {
     String localVarPath = "/fake";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "required_string_group";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("required_string_group", requiredStringGroup));
+    localVarQueryParameterBaseName = "required_int64_group";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("required_int64_group", requiredInt64Group));
+    localVarQueryParameterBaseName = "string_group";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("string_group", stringGroup));
+    localVarQueryParameterBaseName = "int64_group";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("int64_group", int64Group));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));
@@ -1633,17 +1664,29 @@ public class FakeApi {
     String localVarPath = "/fake/test-query-parameters";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "pipe";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("pipes", "pipe", pipe));
+    localVarQueryParameterBaseName = "ioutil";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("csv", "ioutil", ioutil));
+    localVarQueryParameterBaseName = "http";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("ssv", "http", http));
+    localVarQueryParameterBaseName = "url";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("csv", "url", url));
+    localVarQueryParameterBaseName = "context";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("multi", "context", context));
+    localVarQueryParameterBaseName = "language";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("language", language));
+    localVarQueryParameterBaseName = "allowEmpty";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("allowEmpty", allowEmpty));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));

samples/client/petstore/java/native/src/main/java/org/openapitools/client/api/PetApi.java

@@ -296,11 +296,17 @@ public class PetApi {
     String localVarPath = "/pet/findByStatus";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "status";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("csv", "status", status));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));
@@ -380,11 +386,17 @@ public class PetApi {
     String localVarPath = "/pet/findByTags";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "tags";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("csv", "tags", tags));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));

samples/client/petstore/java/native/src/main/java/org/openapitools/client/api/UserApi.java

@@ -527,12 +527,19 @@ public class UserApi {
     String localVarPath = "/user/login";
 
     List<Pair> localVarQueryParams = new ArrayList<>();
+    StringJoiner localVarQueryDeepObjectStringJoiner = new StringJoiner("&");
+    String localVarQueryParameterBaseName;
+    localVarQueryParameterBaseName = "username";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("username", username));
+    localVarQueryParameterBaseName = "password";
     localVarQueryParams.addAll(ApiClient.parameterToPairs("password", password));
 
-    if (!localVarQueryParams.isEmpty()) {
+    if (!localVarQueryParams.isEmpty() || localVarQueryDeepObjectStringJoiner.length() != 0) {
       StringJoiner queryJoiner = new StringJoiner("&");
       localVarQueryParams.forEach(p -> queryJoiner.add(p.getName() + '=' + p.getValue()));
+      if (localVarQueryDeepObjectStringJoiner.length() != 0) {
+        queryJoiner.add(localVarQueryDeepObjectStringJoiner.toString());
+      }
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath + '?' + queryJoiner.toString()));
     } else {
       localVarRequestBuilder.uri(URI.create(memberVarBaseUri + localVarPath));

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/AdditionalPropertiesClass.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -153,5 +156,35 @@ public class AdditionalPropertiesClass {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `map_property` to the URL query string
+    if (getMapProperty() != null) {
+      for (String _key : getMapProperty().keySet()) {
+        joiner.add(String.format("%s[map_property][%s]=%s", prefix, getMapProperty().get(_key), URLEncoder.encode(String.valueOf(getMapProperty().get(_key)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    // add `map_of_map_property` to the URL query string
+    if (getMapOfMapProperty() != null) {
+      for (String _key : getMapOfMapProperty().keySet()) {
+        joiner.add(String.format("%s[map_of_map_property][%s]=%s", prefix, getMapOfMapProperty().get(_key), URLEncoder.encode(String.valueOf(getMapOfMapProperty().get(_key)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/AllOfWithSingleRef.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -136,5 +139,31 @@ public class AllOfWithSingleRef {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `username` to the URL query string
+    if (getUsername() != null) {
+      joiner.add(String.format("%s[username]=%s", prefix, URLEncoder.encode(String.valueOf(getUsername()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `SingleRefType` to the URL query string
+    if (getSingleRefType() != null) {
+      joiner.add(getSingleRefType().toUrlQueryString(prefix + "[SingleRefType]"));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/Animal.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
@@ -151,6 +154,32 @@ public class Animal {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `className` to the URL query string
+    if (getClassName() != null) {
+      joiner.add(String.format("%s[className]=%s", prefix, URLEncoder.encode(String.valueOf(getClassName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `color` to the URL query string
+    if (getColor() != null) {
+      joiner.add(String.format("%s[color]=%s", prefix, URLEncoder.encode(String.valueOf(getColor()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 static {
   // Initialize and register the discriminator mappings.
   Map<String, Class<?>> mappings = new HashMap<String, Class<?>>();

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/ArrayOfArrayOfNumberOnly.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -115,5 +118,30 @@ public class ArrayOfArrayOfNumberOnly {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `ArrayArrayNumber` to the URL query string
+    if (getArrayArrayNumber() != null) {
+      for (int i = 0; i < getArrayArrayNumber().size(); i++) {
+        if (getArrayArrayNumber().get(i) != null) {
+          joiner.add(String.format("%s[ArrayArrayNumber][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getArrayArrayNumber().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+        }
+      }
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/ArrayOfNumberOnly.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -115,5 +118,30 @@ public class ArrayOfNumberOnly {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `ArrayNumber` to the URL query string
+    if (getArrayNumber() != null) {
+      for (int i = 0; i < getArrayNumber().size(); i++) {
+        if (getArrayNumber().get(i) != null) {
+          joiner.add(String.format("%s[ArrayNumber][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getArrayNumber().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+        }
+      }
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/ArrayTest.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -193,5 +196,44 @@ public class ArrayTest {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `array_of_string` to the URL query string
+    if (getArrayOfString() != null) {
+      for (int i = 0; i < getArrayOfString().size(); i++) {
+        joiner.add(String.format("%s[array_of_string][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getArrayOfString().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    // add `array_array_of_integer` to the URL query string
+    if (getArrayArrayOfInteger() != null) {
+      for (int i = 0; i < getArrayArrayOfInteger().size(); i++) {
+        joiner.add(String.format("%s[array_array_of_integer][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getArrayArrayOfInteger().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    // add `array_array_of_model` to the URL query string
+    if (getArrayArrayOfModel() != null) {
+      for (int i = 0; i < getArrayArrayOfModel().size(); i++) {
+        if (getArrayArrayOfModel().get(i) != null) {
+          joiner.add(String.format("%s[array_array_of_model][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getArrayArrayOfModel().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+        }
+      }
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/Capitalization.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -259,5 +262,51 @@ public class Capitalization {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `smallCamel` to the URL query string
+    if (getSmallCamel() != null) {
+      joiner.add(String.format("%s[smallCamel]=%s", prefix, URLEncoder.encode(String.valueOf(getSmallCamel()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `CapitalCamel` to the URL query string
+    if (getCapitalCamel() != null) {
+      joiner.add(String.format("%s[CapitalCamel]=%s", prefix, URLEncoder.encode(String.valueOf(getCapitalCamel()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `small_Snake` to the URL query string
+    if (getSmallSnake() != null) {
+      joiner.add(String.format("%s[small_Snake]=%s", prefix, URLEncoder.encode(String.valueOf(getSmallSnake()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `Capital_Snake` to the URL query string
+    if (getCapitalSnake() != null) {
+      joiner.add(String.format("%s[Capital_Snake]=%s", prefix, URLEncoder.encode(String.valueOf(getCapitalSnake()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `SCA_ETH_Flow_Points` to the URL query string
+    if (getScAETHFlowPoints() != null) {
+      joiner.add(String.format("%s[SCA_ETH_Flow_Points]=%s", prefix, URLEncoder.encode(String.valueOf(getScAETHFlowPoints()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `ATT_NAME` to the URL query string
+    if (getATTNAME() != null) {
+      joiner.add(String.format("%s[ATT_NAME]=%s", prefix, URLEncoder.encode(String.valueOf(getATTNAME()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/Cat.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
@@ -117,6 +120,37 @@ public class Cat extends Animal {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `className` to the URL query string
+    if (getClassName() != null) {
+      joiner.add(String.format("%s[className]=%s", prefix, URLEncoder.encode(String.valueOf(getClassName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `color` to the URL query string
+    if (getColor() != null) {
+      joiner.add(String.format("%s[color]=%s", prefix, URLEncoder.encode(String.valueOf(getColor()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `declawed` to the URL query string
+    if (getDeclawed() != null) {
+      joiner.add(String.format("%s[declawed]=%s", prefix, URLEncoder.encode(String.valueOf(getDeclawed()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 static {
   // Initialize and register the discriminator mappings.
   Map<String, Class<?>> mappings = new HashMap<String, Class<?>>();

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/CatAllOf.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -104,5 +107,26 @@ public class CatAllOf {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `declawed` to the URL query string
+    if (getDeclawed() != null) {
+      joiner.add(String.format("%s[declawed]=%s", prefix, URLEncoder.encode(String.valueOf(getDeclawed()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/Category.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -135,5 +138,31 @@ public class Category {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `id` to the URL query string
+    if (getId() != null) {
+      joiner.add(String.format("%s[id]=%s", prefix, URLEncoder.encode(String.valueOf(getId()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `name` to the URL query string
+    if (getName() != null) {
+      joiner.add(String.format("%s[name]=%s", prefix, URLEncoder.encode(String.valueOf(getName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/ClassModel.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -104,5 +107,26 @@ public class ClassModel {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `_class` to the URL query string
+    if (getPropertyClass() != null) {
+      joiner.add(String.format("%s[_class]=%s", prefix, URLEncoder.encode(String.valueOf(getPropertyClass()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/Client.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -104,5 +107,26 @@ public class Client {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `client` to the URL query string
+    if (getClient() != null) {
+      joiner.add(String.format("%s[client]=%s", prefix, URLEncoder.encode(String.valueOf(getClient()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/DeprecatedObject.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -106,5 +109,26 @@ public class DeprecatedObject {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `name` to the URL query string
+    if (getName() != null) {
+      joiner.add(String.format("%s[name]=%s", prefix, URLEncoder.encode(String.valueOf(getName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/Dog.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
@@ -117,6 +120,37 @@ public class Dog extends Animal {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `className` to the URL query string
+    if (getClassName() != null) {
+      joiner.add(String.format("%s[className]=%s", prefix, URLEncoder.encode(String.valueOf(getClassName()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `color` to the URL query string
+    if (getColor() != null) {
+      joiner.add(String.format("%s[color]=%s", prefix, URLEncoder.encode(String.valueOf(getColor()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `breed` to the URL query string
+    if (getBreed() != null) {
+      joiner.add(String.format("%s[breed]=%s", prefix, URLEncoder.encode(String.valueOf(getBreed()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 static {
   // Initialize and register the discriminator mappings.
   Map<String, Class<?>> mappings = new HashMap<String, Class<?>>();

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/DogAllOf.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -104,5 +107,26 @@ public class DogAllOf {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `breed` to the URL query string
+    if (getBreed() != null) {
+      joiner.add(String.format("%s[breed]=%s", prefix, URLEncoder.encode(String.valueOf(getBreed()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/EnumArrays.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
@@ -215,5 +218,33 @@ public class EnumArrays {
     return o.toString().replace("\n", "\n    ");
   }
 
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    StringJoiner joiner = new StringJoiner("&");
+
+    // add `just_symbol` to the URL query string
+    if (getJustSymbol() != null) {
+      joiner.add(String.format("%s[just_symbol]=%s", prefix, URLEncoder.encode(String.valueOf(getJustSymbol()), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+    }
+
+    // add `array_enum` to the URL query string
+    if (getArrayEnum() != null) {
+      for (int i = 0; i < getArrayEnum().size(); i++) {
+        joiner.add(String.format("%s[array_enum][%d]=%s", prefix, i, URLEncoder.encode(String.valueOf(getArrayEnum().get(i)), StandardCharsets.UTF_8).replaceAll("\\+", "%20")));
+      }
+    }
+
+    return joiner.toString();
+  }
 }
 

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/EnumClass.java

@@ -13,10 +13,13 @@
 
 package org.openapitools.client.model;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.HashMap;
+import java.util.StringJoiner;
 import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 
@@ -59,5 +62,20 @@ public enum EnumClass {
     }
     throw new IllegalArgumentException("Unexpected value '" + value + "'");
   }
+
+  /**
+   * Convert the instance into URL query string.
+   *
+   * @param prefix prefix of the query string
+   * @return URL query string
+   */
+  public String toUrlQueryString(String prefix) {
+    if (prefix == null) {
+      prefix = "";
+    }
+
+    return String.format("%s=%s", prefix, this.toString());
+  }
+
 }