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

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());
+  }
+
 }
 

samples/client/petstore/java/native/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/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/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/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/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/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/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/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/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/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/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/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/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/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/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/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/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/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/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/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/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/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/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/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/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/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/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/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/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/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/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();
+  }
 }