Support Json-serialized query parameters in Spring client RestClient and WebClient (#21725)

* Add so that a query parameter can be serialized as Json in the Spring clients RestClient and WebClient

* Update samples

* Add clientCodeGen test

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

@@ -6,6 +6,7 @@ package {{invokerPackage}};
 import com.fasterxml.jackson.dataformat.xml.XmlMapper;
 import com.fasterxml.jackson.dataformat.xml.ser.ToXmlGenerator;
 {{/withXml}}
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
@@ -503,6 +504,36 @@ public class ApiClient{{#jsr310}} extends JavaTimeFormatter{{/jsr310}} {
         }
     }
 
+    /**
+    * Converts a parameter to a {@link MultiValueMap} containing Json-serialized values for use in REST requests
+    * @param collectionFormat The format to convert to
+    * @param name The name of the parameter
+    * @param value The parameter's value
+    * @return a Map containing the Json-serialized String value(s) of the input parameter
+    */
+    public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionFormat collectionFormat, String name, Object value) {
+        Collection<?> valueCollection;
+        if (value instanceof Collection) {
+            valueCollection = (Collection<?>) value;
+        } else {
+            try {
+                return parameterToMultiValueMap(collectionFormat, name, objectMapper.writeValueAsString(value));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        List<String> values = new ArrayList<>();
+        for(Object o : valueCollection) {
+            try {
+                values.add(objectMapper.writeValueAsString(o));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+    }
+
     /**
      * Converts a parameter to a {@link MultiValueMap} for use in REST requests
      * @param collectionFormat The format to convert to

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

@@ -108,10 +108,28 @@ public class {{classname}} {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
         {{#hasQueryParams}}
 
-        {{#queryParams}}{{#isExplode}}{{#hasVars}}{{#vars}}queryParams.putAll(apiClient.parameterToMultiValueMap({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}.{{getter}}()));
-        {{/vars}}{{/hasVars}}{{^hasVars}}queryParams.putAll(apiClient.parameterToMultiValueMap({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}));
-        {{/hasVars}}{{/isExplode}}{{^isExplode}}queryParams.putAll(apiClient.parameterToMultiValueMap({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}));
-        {{/isExplode}}{{/queryParams}}{{/hasQueryParams}}{{#hasHeaderParams}}
+            {{#queryParams}}
+            {{#queryIsJsonMimeType}}
+        queryParams.putAll(apiClient.parameterToMultiValueMapJson({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}));
+            {{/queryIsJsonMimeType}}
+            {{^queryIsJsonMimeType}}
+            {{#isExplode}}
+                {{#hasVars}}
+                    {{#vars}}
+        queryParams.putAll(apiClient.parameterToMultiValueMap({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}.{{getter}}()));
+                    {{/vars}}
+                {{/hasVars}}
+                {{^hasVars}}
+        queryParams.putAll(apiClient.parameterToMultiValueMap({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}));
+                {{/hasVars}}
+            {{/isExplode}}
+            {{^isExplode}}
+        queryParams.putAll(apiClient.parameterToMultiValueMap({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}));
+            {{/isExplode}}
+            {{/queryIsJsonMimeType}}
+            {{/queryParams}}
+        {{/hasQueryParams}}
+        {{#hasHeaderParams}}
 
         {{#headerParams}}
         if ({{paramName}} != null)

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

@@ -2,6 +2,7 @@
 
 package {{invokerPackage}};
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
@@ -446,6 +447,36 @@ public class ApiClient{{#jsr310}} extends JavaTimeFormatter{{/jsr310}} {
         }
     }
 
+    /**
+    * Converts a parameter to a {@link MultiValueMap} containing Json-serialized values for use in REST requests
+    * @param collectionFormat The format to convert to
+    * @param name The name of the parameter
+    * @param value The parameter's value
+    * @return a Map containing the Json-serialized String value(s) of the input parameter
+    */
+    public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionFormat collectionFormat, String name, Object value) {
+        Collection<?> valueCollection;
+        if (value instanceof Collection) {
+            valueCollection = (Collection<?>) value;
+        } else {
+            try {
+                return parameterToMultiValueMap(collectionFormat, name, objectMapper.writeValueAsString(value));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        List<String> values = new ArrayList<>();
+        for(Object o : valueCollection) {
+            try {
+                values.add(objectMapper.writeValueAsString(o));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+    }
+
     /**
      * Converts a parameter to a {@link MultiValueMap} for use in REST requests
      * @param collectionFormat The format to convert to

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

@@ -110,10 +110,28 @@ public class {{classname}} {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
         {{#hasQueryParams}}
 
-        {{#queryParams}}{{#isExplode}}{{#hasVars}}{{#vars}}queryParams.putAll(apiClient.parameterToMultiValueMap({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}.{{getter}}()));
-        {{/vars}}{{/hasVars}}{{^hasVars}}queryParams.putAll(apiClient.parameterToMultiValueMap({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}));
-        {{/hasVars}}{{/isExplode}}{{^isExplode}}queryParams.putAll(apiClient.parameterToMultiValueMap({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}));
-        {{/isExplode}}{{/queryParams}}{{/hasQueryParams}}{{#hasHeaderParams}}
+            {{#queryParams}}
+            {{#queryIsJsonMimeType}}
+        queryParams.putAll(apiClient.parameterToMultiValueMapJson({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}));
+            {{/queryIsJsonMimeType}}
+            {{^queryIsJsonMimeType}}
+            {{#isExplode}}
+                {{#hasVars}}
+                    {{#vars}}
+        queryParams.putAll(apiClient.parameterToMultiValueMap({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}.{{getter}}()));
+                    {{/vars}}
+                {{/hasVars}}
+                {{^hasVars}}
+        queryParams.putAll(apiClient.parameterToMultiValueMap({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}));
+                {{/hasVars}}
+            {{/isExplode}}
+            {{^isExplode}}
+        queryParams.putAll(apiClient.parameterToMultiValueMap({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}));
+            {{/isExplode}}
+            {{/queryIsJsonMimeType}}
+            {{/queryParams}}
+        {{/hasQueryParams}}
+        {{#hasHeaderParams}}
 
         {{#headerParams}}
         if ({{paramName}} != null)

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

@@ -47,6 +47,7 @@ import org.openapitools.codegen.model.OperationMap;
 import org.openapitools.codegen.model.OperationsMap;
 import org.openapitools.codegen.testutils.ConfigAssert;
 import org.testng.annotations.DataProvider;
+import org.testng.annotations.Parameters;
 import org.testng.annotations.Test;
 
 import java.io.File;
@@ -73,6 +74,8 @@ import static org.testng.Assert.*;
 
 public class JavaClientCodegenTest {
 
+    private static final String JAVA_GENERATOR = "java";
+
     // This is the kind of information that ideally would be defined and available system-wide
     @Getter
     enum Library {
@@ -299,7 +302,7 @@ public class JavaClientCodegenTest {
     public void testGeneratedAuthClassesJersey() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.JERSEY3)
                 .setAdditionalProperties(Map.of(CodegenConstants.API_PACKAGE, "xyz.abcdef.api"))
                 .setInputSpec("src/test/resources/3_0/petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml")
@@ -322,7 +325,7 @@ public class JavaClientCodegenTest {
         final CodegenConfigurator configurator = new CodegenConfigurator()
                 .addTypeMapping("OffsetDateTime", "Instant")
                 .addImportMapping("OffsetDateTime", "java.time.Instant")
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setInputSpec("src/test/resources/3_0/echo_api.yaml")
                 .setOutputDir(output.toString().replace("\\", "/"));
 
@@ -414,7 +417,7 @@ public class JavaClientCodegenTest {
     public void testGeneratePing() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.OKHTTP_GSON)
                 .setAdditionalProperties(Map.of(CodegenConstants.API_PACKAGE, "xyz.abcdef.api"))
                 .setInputSpec("src/test/resources/3_0/ping.yaml")
@@ -471,7 +474,7 @@ public class JavaClientCodegenTest {
     public void testGeneratePingSomeObj() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .addAdditionalProperty(CodegenConstants.MODEL_PACKAGE, "zz.yyyy.model.xxxx")
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "zz.yyyy.api.xxxx")
                 .addAdditionalProperty(CodegenConstants.INVOKER_PACKAGE, "zz.yyyy.invoker.xxxx")
@@ -534,7 +537,7 @@ public class JavaClientCodegenTest {
     public void testJdkHttpClient() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.NATIVE)
                 .setAdditionalProperties(Map.of(CodegenConstants.API_PACKAGE, "xyz.abcdef.api"))
                 .setInputSpec("src/test/resources/3_0/ping.yaml")
@@ -561,7 +564,7 @@ public class JavaClientCodegenTest {
     public void testJdkHttpClientWithUseBeanValidationEnabled() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.NATIVE)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.USE_BEANVALIDATION, true)
@@ -580,7 +583,7 @@ public class JavaClientCodegenTest {
     public void testJdkHttpClientWithAndWithoutDiscriminator() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.NATIVE)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(CodegenConstants.MODEL_PACKAGE, "xyz.abcdef.model")
@@ -603,7 +606,7 @@ public class JavaClientCodegenTest {
     public void testJdkHttpAsyncClient() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.ASYNC_NATIVE, true)
                 .setLibrary(JavaClientCodegen.NATIVE)
@@ -685,7 +688,7 @@ public class JavaClientCodegenTest {
     public void testAuthorizationScopeValues_Issue6733() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTEASY)
                 .setValidateSpec(false)
                 .setInputSpec("src/test/resources/3_0/regression-6734.yaml")
@@ -709,7 +712,7 @@ public class JavaClientCodegenTest {
     public void testTypedAndNonTypedComposedSchemaGeneration_3_1() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTEASY)
                 .setValidateSpec(false)
                 .setInputSpec("src/test/resources/3_1/composed-schemas-with-and-without-type.yaml")
@@ -732,7 +735,7 @@ public class JavaClientCodegenTest {
     public void testMultiPartSpecifiesFileName_Issue17367() throws IOException {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTEASY)
                 .setValidateSpec(false)
                 .setInputSpec("src/test/resources/3_0/issue-17367.yaml")
@@ -818,7 +821,7 @@ public class JavaClientCodegenTest {
     public void testSchemaMapping() throws IOException {
         final Path output = newTempFolder();
         final ClientOptInput clientOptInput = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTEASY)
                 .setAdditionalProperties(Map.of(CodegenConstants.API_PACKAGE, "xyz.abcdef.api"))
                 .setSchemaMappings(Map.of("TypeAlias", "foo.bar.TypeAlias"))
@@ -868,7 +871,7 @@ public class JavaClientCodegenTest {
     public void testVertXAuthInfoWithHyphenSeparatedSecurityScheme() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.VERTX)
                 .setAdditionalProperties(Map.of(CodegenConstants.API_PACKAGE, "xyz.abcdef.api"))
                 .setInputSpec("src/test/resources/3_0/ping-with-hyphen-separated-security-scheme.yaml")
@@ -1080,7 +1083,7 @@ public class JavaClientCodegenTest {
     public void testRestTemplateFormMultipart() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTTEMPLATE)
                 .setAdditionalProperties(Map.of(CodegenConstants.API_PACKAGE, "xyz.abcdef.api"))
                 .setInputSpec("src/test/resources/3_0/form-multipart-binary-array.yaml")
@@ -1116,7 +1119,7 @@ public class JavaClientCodegenTest {
     public void testWebClientFormMultipart() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.WEBCLIENT)
                 .setAdditionalProperties(Map.of(CodegenConstants.API_PACKAGE, "xyz.abcdef.api"))
                 .setInputSpec("src/test/resources/3_0/form-multipart-binary-array.yaml")
@@ -1146,7 +1149,7 @@ public class JavaClientCodegenTest {
     public void shouldGenerateBlockingAndNoBlockingOperationsForWebClient() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.WEBCLIENT_BLOCKING_OPERATIONS, true)
                 .setLibrary(JavaClientCodegen.WEBCLIENT)
@@ -1176,7 +1179,7 @@ public class JavaClientCodegenTest {
     public void testAllowModelWithNoProperties() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.OKHTTP_GSON)
                 .setInputSpec("src/test/resources/2_0/emptyBaseModel.yaml")
                 .setOutputDir(output.toString().replace("\\", "/"));
@@ -1205,7 +1208,7 @@ public class JavaClientCodegenTest {
     public void testRestTemplateWithUseAbstractionForFiles() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.USE_ABSTRACTION_FOR_FILES, true)
                 .setLibrary(JavaClientCodegen.RESTTEMPLATE)
@@ -1292,7 +1295,7 @@ public class JavaClientCodegenTest {
     public void testCustomMethodParamsAreCamelizedWhenUsingFeign() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(FEIGN)
                 .setInputSpec("src/test/resources/3_0/issue_7791.yaml")
                 .setOutputDir(output.toString().replace("\\", "/"));
@@ -1320,7 +1323,7 @@ public class JavaClientCodegenTest {
     public void testCharsetInContentTypeCorrectlyEncodedForFeignApi_issue19895() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(FEIGN)
                 .setInputSpec("src/test/resources/3_0/issue_19895.yaml")
                 .setOutputDir(output.toString().replace("\\", "/"));
@@ -1353,7 +1356,7 @@ public class JavaClientCodegenTest {
     public void testWebClientWithUseAbstractionForFiles() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.USE_ABSTRACTION_FOR_FILES, true)
                 .setLibrary(JavaClientCodegen.WEBCLIENT)
@@ -1386,7 +1389,8 @@ public class JavaClientCodegenTest {
     @Test
     public void testRestTemplateWithFreeFormInQueryParameters() {
         final Path output = newTempFolder();
-        final CodegenConfigurator configurator = new CodegenConfigurator().setGeneratorName("java")
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTTEMPLATE)
                 .setAdditionalProperties(Map.of(CodegenConstants.API_PACKAGE, "xyz.abcdef.api"))
                 .setInputSpec("src/test/resources/3_0/issue8352.yaml")
@@ -1404,7 +1408,8 @@ public class JavaClientCodegenTest {
     @Test
     public void testWebClientWithFreeFormInQueryParameters() {
         final Path output = newTempFolder();
-        final CodegenConfigurator configurator = new CodegenConfigurator().setGeneratorName("java")
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.WEBCLIENT)
                 .setAdditionalProperties(Map.of(CodegenConstants.API_PACKAGE, "xyz.abcdef.api"))
                 .setInputSpec("src/test/resources/3_0/issue8352.yaml")
@@ -1424,7 +1429,7 @@ public class JavaClientCodegenTest {
     public void testNativeClientWhiteSpacePathParamEncoding() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.NATIVE)
                 .setAdditionalProperties(Map.of(CodegenConstants.API_PACKAGE, "xyz.abcdef.api"))
                 .setInputSpec("src/test/resources/3_0/issue11242.yaml")
@@ -1447,7 +1452,7 @@ public class JavaClientCodegenTest {
     public void testNativeClientExplodedQueryParamObject() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.NATIVE)
                 .setAdditionalProperties(Map.of(CodegenConstants.API_PACKAGE, "xyz.abcdef.api"))
                 .setInputSpec("src/test/resources/3_0/issue4808.yaml")
@@ -1470,7 +1475,7 @@ public class JavaClientCodegenTest {
     public void testDefaultMicroprofileRestClientVersion() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.MICROPROFILE)
                 .setInputSpec("src/test/resources/3_0/petstore.yaml")
                 .setOutputDir(output.toString().replace("\\", "/"));
@@ -1494,7 +1499,7 @@ public class JavaClientCodegenTest {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
                 .setAdditionalProperties(Map.of(JavaClientCodegen.MICROPROFILE_REST_CLIENT_VERSION, "1.4.1"))
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.MICROPROFILE)
                 .setInputSpec("src/test/resources/3_0/petstore.yaml")
                 .setOutputDir(output.toString().replace("\\", "/"));
@@ -1523,7 +1528,7 @@ public class JavaClientCodegenTest {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
                 .setAdditionalProperties(Map.of(JavaClientCodegen.MICROPROFILE_REST_CLIENT_VERSION, "incorrectVersion"))
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.MICROPROFILE)
                 .setInputSpec("src/test/resources/3_0/petstore.yaml")
                 .setOutputDir(output.toString().replace("\\", "/"));
@@ -1538,7 +1543,7 @@ public class JavaClientCodegenTest {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
                 .setAdditionalProperties(Map.of(JavaClientCodegen.MICROPROFILE_REST_CLIENT_VERSION, "3.0"))
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.MICROPROFILE)
                 .setInputSpec("src/test/resources/3_0/petstore.yaml")
                 .setOutputDir(output.toString().replace("\\", "/"));
@@ -1562,7 +1567,7 @@ public class JavaClientCodegenTest {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
                 .setAdditionalProperties(Map.of(JavaClientCodegen.MICROPROFILE_REST_CLIENT_VERSION, "3.0"))
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.MICROPROFILE)
                 .setInputSpec("src/test/resources/bugs/issue_12622.json")
                 .setOutputDir(output.toString().replace("\\", "/"));
@@ -1593,9 +1598,8 @@ public class JavaClientCodegenTest {
         output.deleteOnExit();
 
         final CodegenConfigurator configurator = new CodegenConfigurator()
-
                 .setAdditionalProperties(properties)
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.MICROPROFILE)
                 .setInputSpec("src/test/resources/bugs/issue_18336.yaml")
                 .setOutputDir(output.getAbsolutePath().replace("\\", "/"));
@@ -1620,7 +1624,7 @@ public class JavaClientCodegenTest {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
                 .setAdditionalProperties(Map.of(JavaClientCodegen.MICROPROFILE_REST_CLIENT_VERSION, "3.0"))
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.WEBCLIENT)
                 .setOutputDir(output.toString().replace("\\", "/"))
                 .setInputSpec("src/test/resources/bugs/java-codegen-empty-array-as-default-value/issue_wrong-default.yaml");
@@ -1644,7 +1648,7 @@ public class JavaClientCodegenTest {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
                 .setAdditionalProperties(Map.of(AbstractJavaCodegen.OPENAPI_NULLABLE, "true"))
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.WEBCLIENT)
                 .setInputSpec("src/test/resources/bugs/issue_12790.yaml")
                 .setOutputDir(output.toString().replace("\\", "/"));
@@ -1665,7 +1669,7 @@ public class JavaClientCodegenTest {
     public void testRestTemplateResponseTypeWithUseAbstractionForFiles() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTTEMPLATE)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.USE_ABSTRACTION_FOR_FILES, true)
@@ -1689,7 +1693,7 @@ public class JavaClientCodegenTest {
         final Path output = newTempFolder();
         final String outputPath = output.toString().replace('\\', '/');
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(library.value)
                 .setAdditionalProperties(Map.of(CXFServerFeatures.LOAD_TEST_DATA_FROM_FILE, "true"))
                 .setInputSpec("src/test/resources/3_0/issue_11772.yml")
@@ -1710,7 +1714,8 @@ public class JavaClientCodegenTest {
     @Test
     public void testReferencedHeader2() {
         final Path output = newTempFolder();
-        final CodegenConfigurator configurator = new CodegenConfigurator().setGeneratorName("java")
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName(JAVA_GENERATOR)
                 .setAdditionalProperties(Map.of(BeanValidationFeatures.USE_BEANVALIDATION, "true"))
                 .setInputSpec("src/test/resources/3_0/issue-11340.yaml")
                 .setOutputDir(output.toString().replace("\\", "/"));
@@ -1733,7 +1738,7 @@ public class JavaClientCodegenTest {
     public void testReturnTypeMapping() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setInputSpec("src/test/resources/3_0/issue14525.yaml")
                 .addTypeMapping("array", "Stack")
                 .addImportMapping("Stack", "java.util.Stack")
@@ -1749,7 +1754,7 @@ public class JavaClientCodegenTest {
     public void testNativeClientExplodedQueryParamWithArrayProperty() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.NATIVE)
                 .setAdditionalProperties(Map.of(CodegenConstants.API_PACKAGE, "xyz.abcdef.api"))
                 .setInputSpec("src/test/resources/3_0/exploded-query-param-array.yaml")
@@ -1767,7 +1772,7 @@ public class JavaClientCodegenTest {
     public void testJdkHttpClientWithAndWithoutParentExtension() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 // use default `okhttp-gson`
                 //.setLibrary(JavaClientCodegen.NATIVE)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
@@ -1966,7 +1971,7 @@ public class JavaClientCodegenTest {
         final Path output = newTempFolder();
 
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(library)
                 .setAdditionalProperties(properties)
                 .setInputSpec(pathToSpecification)
@@ -2073,7 +2078,7 @@ public class JavaClientCodegenTest {
     public void testDeprecatedProperty() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.OKHTTP_GSON)
                 .setInputSpec("src/test/resources/3_0/deprecated-properties.yaml")
                 .setOutputDir(output.toString().replace("\\", "/"));
@@ -2093,7 +2098,7 @@ public class JavaClientCodegenTest {
     public void testDeprecatedPropertyJersey3() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.JERSEY3)
                 .setInputSpec("src/test/resources/3_0/deprecated-properties.yaml")
                 .setOutputDir(output.toString().replace("\\", "/"));
@@ -2122,7 +2127,7 @@ public class JavaClientCodegenTest {
     public void shouldNotAddAdditionalModelAnnotationsToAbstractOpenApiSchema_issue15684(String library) {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(library)
                 .addAdditionalProperty(AbstractJavaCodegen.ADDITIONAL_MODEL_TYPE_ANNOTATIONS, "@annotation1;@annotation2")
                 .setInputSpec("src/test/resources/3_0/deprecated-properties.yaml")
@@ -2145,7 +2150,7 @@ public class JavaClientCodegenTest {
     public void testRestTemplateWithGeneratedClientAsBeanDisabled() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.GENERATE_CLIENT_AS_BEAN, false)
                 .setLibrary(JavaClientCodegen.RESTTEMPLATE)
@@ -2163,7 +2168,7 @@ public class JavaClientCodegenTest {
     public void testRestTemplateWithGeneratedClientAsBeanEnabled() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.GENERATE_CLIENT_AS_BEAN, true)
                 .setLibrary(JavaClientCodegen.RESTTEMPLATE)
@@ -2181,7 +2186,7 @@ public class JavaClientCodegenTest {
     public void testRestTemplateWithUseBeanValidationEnabled() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTTEMPLATE)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.USE_BEANVALIDATION, true)
@@ -2199,7 +2204,7 @@ public class JavaClientCodegenTest {
     public void testRestTemplateWithUseBeanValidationDisabled() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTTEMPLATE)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.USE_BEANVALIDATION, false)
@@ -2217,7 +2222,7 @@ public class JavaClientCodegenTest {
     public void testRestTemplateWithPerformBeanValidationEnabled() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTTEMPLATE)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.PERFORM_BEANVALIDATION, true)
@@ -2235,7 +2240,7 @@ public class JavaClientCodegenTest {
     public void testRestTemplateWithPerformBeanValidationDisabled() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.PERFORM_BEANVALIDATION, false)
                 .setLibrary(JavaClientCodegen.RESTTEMPLATE)
@@ -2252,7 +2257,7 @@ public class JavaClientCodegenTest {
     @Test
     public void testLogicToAvoidStackOverflow() {
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.GENERATE_CLIENT_AS_BEAN, true)
                 .setLibrary(JavaClientCodegen.RESTTEMPLATE)
@@ -2268,7 +2273,7 @@ public class JavaClientCodegenTest {
     public void testWebClientSupportListOfStringReturnType_issue7118() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.USE_ABSTRACTION_FOR_FILES, true)
                 .setLibrary(JavaClientCodegen.WEBCLIENT)
@@ -2346,7 +2351,7 @@ public class JavaClientCodegenTest {
     public void testWebClientResponseTypeWithUseAbstractionForFiles_issue16589() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.USE_ABSTRACTION_FOR_FILES, true)
                 .setLibrary(JavaClientCodegen.WEBCLIENT)
@@ -2502,7 +2507,7 @@ public class JavaClientCodegenTest {
     private void testHandleURIEnum(String library, String[] expectedInnerEnumLines, String[] expectedEnumLines) {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(library)
                 .setInputSpec("src/test/resources/3_0/enum-and-inner-enum-uri.yaml")
                 .setOutputDir(output.toString().replace("\\", "/"));
@@ -2525,7 +2530,7 @@ public class JavaClientCodegenTest {
     public void testQueryParamsExploded_whenQueryParamIsNull() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTTEMPLATE)
                 .setAdditionalProperties(Map.of(CodegenConstants.API_PACKAGE, "xyz.abcdef.api"))
                 .setInputSpec("src/test/resources/3_0/issue_17555.yaml")
@@ -2602,7 +2607,7 @@ public class JavaClientCodegenTest {
     public void testRestClientFormMultipart() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTCLIENT)
                 .setAdditionalProperties(Map.of(CodegenConstants.API_PACKAGE, "xyz.abcdef.api"))
                 .setInputSpec("src/test/resources/3_0/form-multipart-binary-array.yaml")
@@ -2632,7 +2637,7 @@ public class JavaClientCodegenTest {
     public void testRestClientWithUseAbstractionForFiles() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.USE_ABSTRACTION_FOR_FILES, true)
                 .setLibrary(JavaClientCodegen.RESTCLIENT)
@@ -2661,7 +2666,8 @@ public class JavaClientCodegenTest {
     @Test
     public void testRestClientWithFreeFormInQueryParameters() {
         final Path output = newTempFolder();
-        final CodegenConfigurator configurator = new CodegenConfigurator().setGeneratorName("java")
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTCLIENT)
                 .setAdditionalProperties(Map.of(CodegenConstants.API_PACKAGE, "xyz.abcdef.api"))
                 .setInputSpec("src/test/resources/3_0/issue8352.yaml")
@@ -2678,7 +2684,7 @@ public class JavaClientCodegenTest {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
                 .addAdditionalProperty(AbstractJavaCodegen.OPENAPI_NULLABLE, "true")
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTCLIENT)
                 .setInputSpec("src/test/resources/bugs/issue_12790.yaml")
                 .setOutputDir(output.toString().replace("\\", "/"));
@@ -2700,7 +2706,7 @@ public class JavaClientCodegenTest {
     public void testRestClientSupportListOfStringReturnType_issue7118() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.USE_ABSTRACTION_FOR_FILES, true)
                 .setLibrary(JavaClientCodegen.RESTCLIENT)
@@ -2727,7 +2733,7 @@ public class JavaClientCodegenTest {
     public void testRestClientResponseTypeWithUseAbstractionForFiles_issue16589() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .addAdditionalProperty(CodegenConstants.API_PACKAGE, "xyz.abcdef.api")
                 .addAdditionalProperty(JavaClientCodegen.USE_ABSTRACTION_FOR_FILES, true)
                 .setLibrary(JavaClientCodegen.RESTCLIENT)
@@ -2797,7 +2803,7 @@ public class JavaClientCodegenTest {
         final CodegenConfigurator configurator = new CodegenConfigurator()
                 .addAdditionalProperty(SERIALIZATION_LIBRARY, Serializer.GSON)
                 .addAdditionalProperty(OPENAPI_NULLABLE, "false")
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(library.getValue())
                 .setInputSpec("src/test/resources/3_0/java/autoset_constant.yaml")
                 .setOutputDir(newTempFolder().toString());
@@ -2817,7 +2823,7 @@ public class JavaClientCodegenTest {
     @Test
     void doesNotGenerateJacksonJsonFormatAnnotation_whenLibraryIsGson_andSerializeBigDecimalAsStringIsTrue() {
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.OKHTTP_GSON)
                 .addAdditionalProperty(CodegenConstants.SERIALIZATION_LIBRARY, SERIALIZATION_LIBRARY_GSON)
                 .addAdditionalProperty(CodegenConstants.SERIALIZE_BIG_DECIMAL_AS_STRING, true)
@@ -2844,7 +2850,7 @@ public class JavaClientCodegenTest {
     @Test
     void generatesJacksonJsonFormatAnnotation_whenLibraryIsJackson_andSerializeBigDecimalAsStringIsTrue() {
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.NATIVE)
                 .addAdditionalProperty(CodegenConstants.SERIALIZATION_LIBRARY, SERIALIZATION_LIBRARY_JACKSON)
                 .addAdditionalProperty(CodegenConstants.SERIALIZE_BIG_DECIMAL_AS_STRING, true)
@@ -2881,7 +2887,7 @@ public class JavaClientCodegenTest {
                 .addGlobalProperty(CodegenConstants.MODELS, "Pet")
                 .addGlobalProperty(CodegenConstants.MODEL_DOCS, null)
                 .addGlobalProperty(CodegenConstants.MODEL_TESTS, null)
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setInputSpec("src/test/resources/3_0/java/xml-annotations-test.yaml")
                 .setLibrary(library.value)
                 .setOutputDir(newTempFolder().toString());
@@ -3021,7 +3027,7 @@ public class JavaClientCodegenTest {
                 .addGlobalProperty(CodegenConstants.MODELS, "Pet")
                 .addGlobalProperty(CodegenConstants.MODEL_DOCS, null)
                 .addGlobalProperty(CodegenConstants.MODEL_TESTS, null)
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(library.value)
                 .setInputSpec("src/test/resources/3_0/java/xml-annotations-test.yaml")
                 .setOutputDir(newTempFolder().toString());
@@ -3166,7 +3172,7 @@ public class JavaClientCodegenTest {
     public void testRestClientWithXML_issue_19137() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTCLIENT)
                 .setAdditionalProperties(Map.of(
                         CodegenConstants.API_PACKAGE, "xyz.abcdef.api",
@@ -3189,7 +3195,7 @@ public class JavaClientCodegenTest {
     public void testRestClientWithUseSingleRequestParameter_issue_19406() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTCLIENT)
                 .setAdditionalProperties(Map.of(
                         CodegenConstants.API_PACKAGE, "xyz.abcdef.api",
@@ -3216,7 +3222,7 @@ public class JavaClientCodegenTest {
     public void testRestClientWithUseSingleRequestParameter_static_issue_20668() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTCLIENT)
                 .setAdditionalProperties(Map.of(
                         CodegenConstants.API_PACKAGE, "xyz.abcdef.api",
@@ -3252,7 +3258,7 @@ public class JavaClientCodegenTest {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
                 .setValidateSpec(false)
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.RESTCLIENT)
                 .setAdditionalProperties(Map.of(
                         CodegenConstants.API_PACKAGE, "xyz.abcdef.api",
@@ -3288,7 +3294,7 @@ public class JavaClientCodegenTest {
     public void testWebClientWithUseSingleRequestParameter_issue_19407() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.WEBCLIENT)
                 .setAdditionalProperties(Map.of(
                         CodegenConstants.API_PACKAGE, "xyz.abcdef.api",
@@ -3318,7 +3324,7 @@ public class JavaClientCodegenTest {
     public void testWebClientWithUseSingleRequestParameter_static() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.WEBCLIENT)
                 .setAdditionalProperties(Map.of(
                         CodegenConstants.API_PACKAGE, "xyz.abcdef.api",
@@ -3348,7 +3354,7 @@ public class JavaClientCodegenTest {
     public void testWebClientWithUseSingleRequestParameter_static_issue_20668() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.WEBCLIENT)
                 .setAdditionalProperties(Map.of(
                         CodegenConstants.API_PACKAGE, "xyz.abcdef.api",
@@ -3381,7 +3387,7 @@ public class JavaClientCodegenTest {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
                 .setValidateSpec(false)
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setAdditionalProperties(Map.of(
                         CodegenConstants.API_PACKAGE, "xyz.abcdef.api"
                 ))
@@ -3411,7 +3417,7 @@ public class JavaClientCodegenTest {
         output.deleteOnExit();
 
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.NATIVE)
                 .setAdditionalProperties(properties)
                 .setInputSpec("src/test/resources/3_0/java/native/issue13968.yaml")
@@ -3448,7 +3454,7 @@ public class JavaClientCodegenTest {
         output.deleteOnExit();
 
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JavaClientCodegen.NATIVE)
                 .setAdditionalProperties(properties)
                 .setInputSpec("src/test/resources/3_0/java/native/issue13968.yaml")
@@ -3493,7 +3499,7 @@ public class JavaClientCodegenTest {
     public void testClassesAreValidJavaJersey2() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JERSEY2)
                 .setSchemaMappings(Map.of(
                         "A", "some.pkg.A",
@@ -3530,7 +3536,7 @@ public class JavaClientCodegenTest {
     public void testClassesAreValidJavaJersey3() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(JERSEY3)
                 .setSchemaMappings(Map.of(
                         "A", "some.pkg.A",
@@ -3567,7 +3573,7 @@ public class JavaClientCodegenTest {
     public void testClassesAreValidJavaOkHttpGson() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(OKHTTP_GSON)
                 .setSchemaMappings(Map.of(
                         "A", "some.pkg.A",
@@ -3614,7 +3620,7 @@ public class JavaClientCodegenTest {
         Generator generator = new DefaultGenerator();
         CodegenConfigurator configurator = new CodegenConfigurator()
                 .setInputSpec("src/test/resources/3_1/issue_21051.yaml")
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setAdditionalProperties(properties)
                 .setOutputDir(output.getAbsolutePath());
         ClientOptInput clientOptInput = configurator.toClientOptInput();
@@ -3670,7 +3676,7 @@ public class JavaClientCodegenTest {
     public void testNativeClientWithUseSingleRequestParameter() {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(NATIVE)
                 .setAdditionalProperties(Map.of(
                         CodegenConstants.API_PACKAGE, "xyz.abcdef.api",
@@ -3710,7 +3716,7 @@ public class JavaClientCodegenTest {
         Generator generator = new DefaultGenerator();
         CodegenConfigurator configurator = new CodegenConfigurator()
                 .setInputSpec("src/test/resources/3_0/oneOf.yaml")
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(library.value)
                 .setAdditionalProperties(properties)
                 .setOutputDir(output.getAbsolutePath());
@@ -3770,7 +3776,7 @@ public class JavaClientCodegenTest {
     public void sealedInterfaceScenariosRestClient(String apiFile, Map<String, String> definitions) {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(RESTCLIENT)
                 .setAdditionalProperties(Map.of(
                         USE_ONE_OF_INTERFACES, "true",
@@ -3789,7 +3795,7 @@ public class JavaClientCodegenTest {
     public void sealedInterfaceScenariosWebClient(String apiFile, Map<String, String> definitions) {
         final Path output = newTempFolder();
         final CodegenConfigurator configurator = new CodegenConfigurator()
-                .setGeneratorName("java")
+                .setGeneratorName(JAVA_GENERATOR)
                 .setLibrary(WEBCLIENT)
                 .setAdditionalProperties(Map.of(
                         USE_ONE_OF_INTERFACES, "true",
@@ -3805,4 +3811,30 @@ public class JavaClientCodegenTest {
         assertFileContains(output.resolve("pom.xml"), "<source>17</source>");
         assertFileNotContains(output.resolve("pom.xml"), "<source>1.8</source>");
     }
+
+    @Test(dataProvider = "springClients")
+    public void queryParameterJsonSerialization(String library) {
+        final Path output = newTempFolder();
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName(JAVA_GENERATOR)
+                .setLibrary(library)
+                .setInputSpec("src/test/resources/3_0/echo_api.yaml")
+                .setOutputDir(output.toString().replace("\\", "/"));
+
+        new DefaultGenerator().opts(configurator.toClientOptInput()).generate();
+        assertFileContains(
+                output.resolve("src/main/java/org/openapitools/client/api/QueryApi.java"),
+                "queryParams.putAll(apiClient.parameterToMultiValueMapJson(null, \"json_serialized_object_ref_string_query\", jsonSerializedObjectRefStringQuery));"
+        );
+        assertFileContains(
+                output.resolve("src/main/java/org/openapitools/client/api/QueryApi.java"),
+                "queryParams.putAll(apiClient.parameterToMultiValueMapJson(ApiClient.CollectionFormat" +
+                ".valueOf(\"csv\".toUpperCase(Locale.ROOT)), \"json_serialized_object_array_ref_string_query\", jsonSerializedObjectArrayRefStringQuery));"
+        );
+    }
+
+    @DataProvider(name = "springClients")
+    public static Object[] springClients() {
+        return new Object[]{RESTCLIENT, WEBCLIENT};
+    }
 }

samples/client/echo_api/java/restclient/src/main/java/org/openapitools/client/ApiClient.java

@@ -13,6 +13,7 @@
 
 package org.openapitools.client;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
@@ -438,6 +439,36 @@ public class ApiClient extends JavaTimeFormatter {
         }
     }
 
+    /**
+    * Converts a parameter to a {@link MultiValueMap} containing Json-serialized values for use in REST requests
+    * @param collectionFormat The format to convert to
+    * @param name The name of the parameter
+    * @param value The parameter's value
+    * @return a Map containing the Json-serialized String value(s) of the input parameter
+    */
+    public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionFormat collectionFormat, String name, Object value) {
+        Collection<?> valueCollection;
+        if (value instanceof Collection) {
+            valueCollection = (Collection<?>) value;
+        } else {
+            try {
+                return parameterToMultiValueMap(collectionFormat, name, objectMapper.writeValueAsString(value));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        List<String> values = new ArrayList<>();
+        for(Object o : valueCollection) {
+            try {
+                values.add(objectMapper.writeValueAsString(o));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+    }
+
     /**
      * Converts a parameter to a {@link MultiValueMap} for use in REST requests
      * @param collectionFormat The format to convert to

samples/client/echo_api/java/restclient/src/main/java/org/openapitools/client/api/HeaderApi.java

@@ -66,7 +66,6 @@ public class HeaderApi {
         final MultiValueMap<String, String> cookieParams = new LinkedMultiValueMap<>();
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
-
         if (integerHeader != null)
         headerParams.add("integer_header", apiClient.parameterToString(integerHeader));
         if (booleanHeader != null)

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

@@ -71,7 +71,7 @@ public class QueryApi {
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_nonref_string_query", enumNonrefStringQuery));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_ref_string_query", enumRefStringQuery));
-        
+
         final String[] localVarAccepts = { 
             "text/plain"
         };
@@ -149,7 +149,7 @@ public class QueryApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "datetime_query", datetimeQuery));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "date_query", dateQuery));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "string_query", stringQuery));
-        
+
         final String[] localVarAccepts = { 
             "text/plain"
         };
@@ -230,7 +230,7 @@ public class QueryApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "integer_query", integerQuery));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "boolean_query", booleanQuery));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "string_query", stringQuery));
-        
+
         final String[] localVarAccepts = { 
             "text/plain"
         };
@@ -312,7 +312,7 @@ public class QueryApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "photoUrls", queryObject.getPhotoUrls()));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "tags", queryObject.getTags()));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "status", queryObject.getStatus()));
-        
+
         final String[] localVarAccepts = { 
             "text/plain"
         };
@@ -383,7 +383,7 @@ public class QueryApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query_object", queryObject));
-        
+
         final String[] localVarAccepts = { 
             "text/plain"
         };
@@ -454,7 +454,7 @@ public class QueryApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "query_object", queryObject));
-        
+
         final String[] localVarAccepts = { 
             "text/plain"
         };
@@ -525,7 +525,7 @@ public class QueryApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "query_object", queryObject));
-        
+
         final String[] localVarAccepts = { 
             "text/plain"
         };
@@ -596,7 +596,7 @@ public class QueryApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "values", queryObject.getValues()));
-        
+
         final String[] localVarAccepts = { 
             "text/plain"
         };
@@ -672,7 +672,7 @@ public class QueryApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "photoUrls", queryObject.getPhotoUrls()));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "tags", queryObject.getTags()));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "status", queryObject.getStatus()));
-        
+
         final String[] localVarAccepts = { 
             "text/plain"
         };
@@ -743,7 +743,7 @@ public class QueryApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query_object", queryObject));
-        
+
         final String[] localVarAccepts = { 
             "text/plain"
         };
@@ -814,9 +814,9 @@ public class QueryApi {
         final MultiValueMap<String, String> cookieParams = new LinkedMultiValueMap<>();
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
-        queryParams.putAll(apiClient.parameterToMultiValueMap(null, "json_serialized_object_ref_string_query", jsonSerializedObjectRefStringQuery));
-        queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "json_serialized_object_array_ref_string_query", jsonSerializedObjectArrayRefStringQuery));
-        
+        queryParams.putAll(apiClient.parameterToMultiValueMapJson(null, "json_serialized_object_ref_string_query", jsonSerializedObjectRefStringQuery));
+        queryParams.putAll(apiClient.parameterToMultiValueMapJson(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "json_serialized_object_array_ref_string_query", jsonSerializedObjectArrayRefStringQuery));
+
         final String[] localVarAccepts = { 
             "text/plain"
         };

samples/client/others/java/restclient-enum-in-multipart/src/main/java/org/openapitools/client/ApiClient.java

@@ -13,6 +13,7 @@
 
 package org.openapitools.client;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
@@ -437,6 +438,36 @@ public class ApiClient extends JavaTimeFormatter {
         }
     }
 
+    /**
+    * Converts a parameter to a {@link MultiValueMap} containing Json-serialized values for use in REST requests
+    * @param collectionFormat The format to convert to
+    * @param name The name of the parameter
+    * @param value The parameter's value
+    * @return a Map containing the Json-serialized String value(s) of the input parameter
+    */
+    public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionFormat collectionFormat, String name, Object value) {
+        Collection<?> valueCollection;
+        if (value instanceof Collection) {
+            valueCollection = (Collection<?>) value;
+        } else {
+            try {
+                return parameterToMultiValueMap(collectionFormat, name, objectMapper.writeValueAsString(value));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        List<String> values = new ArrayList<>();
+        for(Object o : valueCollection) {
+            try {
+                values.add(objectMapper.writeValueAsString(o));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+    }
+
     /**
      * Converts a parameter to a {@link MultiValueMap} for use in REST requests
      * @param collectionFormat The format to convert to

samples/client/others/java/restclient-useAbstractionForFiles/src/main/java/org/openapitools/client/ApiClient.java

@@ -13,6 +13,7 @@
 
 package org.openapitools.client;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
@@ -436,6 +437,36 @@ public class ApiClient extends JavaTimeFormatter {
         }
     }
 
+    /**
+    * Converts a parameter to a {@link MultiValueMap} containing Json-serialized values for use in REST requests
+    * @param collectionFormat The format to convert to
+    * @param name The name of the parameter
+    * @param value The parameter's value
+    * @return a Map containing the Json-serialized String value(s) of the input parameter
+    */
+    public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionFormat collectionFormat, String name, Object value) {
+        Collection<?> valueCollection;
+        if (value instanceof Collection) {
+            valueCollection = (Collection<?>) value;
+        } else {
+            try {
+                return parameterToMultiValueMap(collectionFormat, name, objectMapper.writeValueAsString(value));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        List<String> values = new ArrayList<>();
+        for(Object o : valueCollection) {
+            try {
+                values.add(objectMapper.writeValueAsString(o));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+    }
+
     /**
      * Converts a parameter to a {@link MultiValueMap} for use in REST requests
      * @param collectionFormat The format to convert to

samples/client/others/java/webclient-sealedInterface/src/main/java/org/openapitools/client/ApiClient.java

@@ -13,6 +13,7 @@
 
 package org.openapitools.client;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
@@ -415,6 +416,36 @@ public class ApiClient extends JavaTimeFormatter {
         }
     }
 
+    /**
+    * Converts a parameter to a {@link MultiValueMap} containing Json-serialized values for use in REST requests
+    * @param collectionFormat The format to convert to
+    * @param name The name of the parameter
+    * @param value The parameter's value
+    * @return a Map containing the Json-serialized String value(s) of the input parameter
+    */
+    public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionFormat collectionFormat, String name, Object value) {
+        Collection<?> valueCollection;
+        if (value instanceof Collection) {
+            valueCollection = (Collection<?>) value;
+        } else {
+            try {
+                return parameterToMultiValueMap(collectionFormat, name, objectMapper.writeValueAsString(value));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        List<String> values = new ArrayList<>();
+        for(Object o : valueCollection) {
+            try {
+                values.add(objectMapper.writeValueAsString(o));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+    }
+
     /**
      * Converts a parameter to a {@link MultiValueMap} for use in REST requests
      * @param collectionFormat The format to convert to

samples/client/others/java/webclient-useAbstractionForFiles/src/main/java/org/openapitools/client/ApiClient.java

@@ -13,6 +13,7 @@
 
 package org.openapitools.client;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
@@ -415,6 +416,36 @@ public class ApiClient extends JavaTimeFormatter {
         }
     }
 
+    /**
+    * Converts a parameter to a {@link MultiValueMap} containing Json-serialized values for use in REST requests
+    * @param collectionFormat The format to convert to
+    * @param name The name of the parameter
+    * @param value The parameter's value
+    * @return a Map containing the Json-serialized String value(s) of the input parameter
+    */
+    public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionFormat collectionFormat, String name, Object value) {
+        Collection<?> valueCollection;
+        if (value instanceof Collection) {
+            valueCollection = (Collection<?>) value;
+        } else {
+            try {
+                return parameterToMultiValueMap(collectionFormat, name, objectMapper.writeValueAsString(value));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        List<String> values = new ArrayList<>();
+        for(Object o : valueCollection) {
+            try {
+                values.add(objectMapper.writeValueAsString(o));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+    }
+
     /**
      * Converts a parameter to a {@link MultiValueMap} for use in REST requests
      * @param collectionFormat The format to convert to

samples/client/petstore/java/restclient-nullable-arrays/src/main/java/org/openapitools/client/ApiClient.java

@@ -13,6 +13,7 @@
 
 package org.openapitools.client;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
@@ -436,6 +437,36 @@ public class ApiClient extends JavaTimeFormatter {
         }
     }
 
+    /**
+    * Converts a parameter to a {@link MultiValueMap} containing Json-serialized values for use in REST requests
+    * @param collectionFormat The format to convert to
+    * @param name The name of the parameter
+    * @param value The parameter's value
+    * @return a Map containing the Json-serialized String value(s) of the input parameter
+    */
+    public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionFormat collectionFormat, String name, Object value) {
+        Collection<?> valueCollection;
+        if (value instanceof Collection) {
+            valueCollection = (Collection<?>) value;
+        } else {
+            try {
+                return parameterToMultiValueMap(collectionFormat, name, objectMapper.writeValueAsString(value));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        List<String> values = new ArrayList<>();
+        for(Object o : valueCollection) {
+            try {
+                values.add(objectMapper.writeValueAsString(o));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+    }
+
     /**
      * Converts a parameter to a {@link MultiValueMap} for use in REST requests
      * @param collectionFormat The format to convert to

samples/client/petstore/java/restclient-swagger2/src/main/java/org/openapitools/client/ApiClient.java

@@ -13,6 +13,7 @@
 
 package org.openapitools.client;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
@@ -499,6 +500,36 @@ public class ApiClient extends JavaTimeFormatter {
         }
     }
 
+    /**
+    * Converts a parameter to a {@link MultiValueMap} containing Json-serialized values for use in REST requests
+    * @param collectionFormat The format to convert to
+    * @param name The name of the parameter
+    * @param value The parameter's value
+    * @return a Map containing the Json-serialized String value(s) of the input parameter
+    */
+    public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionFormat collectionFormat, String name, Object value) {
+        Collection<?> valueCollection;
+        if (value instanceof Collection) {
+            valueCollection = (Collection<?>) value;
+        } else {
+            try {
+                return parameterToMultiValueMap(collectionFormat, name, objectMapper.writeValueAsString(value));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        List<String> values = new ArrayList<>();
+        for(Object o : valueCollection) {
+            try {
+                values.add(objectMapper.writeValueAsString(o));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+    }
+
     /**
      * Converts a parameter to a {@link MultiValueMap} for use in REST requests
      * @param collectionFormat The format to convert to

samples/client/petstore/java/restclient-swagger2/src/main/java/org/openapitools/client/api/FakeApi.java

@@ -212,7 +212,6 @@ public class FakeApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query_1", query1));
-        
 
         if (header1 != null)
         headerParams.add("header_1", apiClient.parameterToString(header1));
@@ -867,7 +866,7 @@ public class FakeApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query", query));
-        
+
         final String[] localVarAccepts = { };
         final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
         final String[] localVarContentTypes = { 
@@ -1193,7 +1192,6 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_query_integer", enumQueryInteger));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_query_double", enumQueryDouble));
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("multi".toUpperCase(Locale.ROOT)), "enum_query_model_array", enumQueryModelArray));
-        
 
         if (enumHeaderStringArray != null)
         headerParams.add("enum_header_string_array", apiClient.parameterToString(enumHeaderStringArray));
@@ -1318,7 +1316,6 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "required_int64_group", requiredInt64Group));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "string_group", stringGroup));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "int64_group", int64Group));
-        
 
         if (requiredBooleanGroup != null)
         headerParams.add("required_boolean_group", apiClient.parameterToString(requiredBooleanGroup));
@@ -1733,7 +1730,7 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("multi".toUpperCase(Locale.ROOT)), "context", context));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "language", language));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "allowEmpty", allowEmpty));
-        
+
         final String[] localVarAccepts = { };
         final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
         final String[] localVarContentTypes = { };

samples/client/petstore/java/restclient-swagger2/src/main/java/org/openapitools/client/api/PetApi.java

@@ -146,7 +146,6 @@ public class PetApi {
         final MultiValueMap<String, String> cookieParams = new LinkedMultiValueMap<>();
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
-
         if (apiKey != null)
         headerParams.add("api_key", apiClient.parameterToString(apiKey));
         final String[] localVarAccepts = { };
@@ -226,7 +225,7 @@ public class PetApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "status", status));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };
@@ -307,7 +306,7 @@ public class PetApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "tags", tags));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };

samples/client/petstore/java/restclient-swagger2/src/main/java/org/openapitools/client/api/UserApi.java

@@ -442,7 +442,7 @@ public class UserApi {
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "username", username));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "password", password));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };

samples/client/petstore/java/restclient-useSingleRequestParameter-static/src/main/java/org/openapitools/client/ApiClient.java

@@ -13,6 +13,7 @@
 
 package org.openapitools.client;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
@@ -499,6 +500,36 @@ public class ApiClient extends JavaTimeFormatter {
         }
     }
 
+    /**
+    * Converts a parameter to a {@link MultiValueMap} containing Json-serialized values for use in REST requests
+    * @param collectionFormat The format to convert to
+    * @param name The name of the parameter
+    * @param value The parameter's value
+    * @return a Map containing the Json-serialized String value(s) of the input parameter
+    */
+    public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionFormat collectionFormat, String name, Object value) {
+        Collection<?> valueCollection;
+        if (value instanceof Collection) {
+            valueCollection = (Collection<?>) value;
+        } else {
+            try {
+                return parameterToMultiValueMap(collectionFormat, name, objectMapper.writeValueAsString(value));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        List<String> values = new ArrayList<>();
+        for(Object o : valueCollection) {
+            try {
+                values.add(objectMapper.writeValueAsString(o));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+    }
+
     /**
      * Converts a parameter to a {@link MultiValueMap} for use in REST requests
      * @param collectionFormat The format to convert to

samples/client/petstore/java/restclient-useSingleRequestParameter-static/src/main/java/org/openapitools/client/api/FakeApi.java

@@ -303,7 +303,6 @@ public class FakeApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query_1", query1));
-        
 
         if (header1 != null)
         headerParams.add("header_1", apiClient.parameterToString(header1));
@@ -1038,7 +1037,7 @@ public class FakeApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query", query));
-        
+
         final String[] localVarAccepts = { };
         final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
         final String[] localVarContentTypes = { 
@@ -1739,7 +1738,6 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_query_integer", enumQueryInteger));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_query_double", enumQueryDouble));
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("multi".toUpperCase(Locale.ROOT)), "enum_query_model_array", enumQueryModelArray));
-        
 
         if (enumHeaderStringArray != null)
         headerParams.add("enum_header_string_array", apiClient.parameterToString(enumHeaderStringArray));
@@ -1988,7 +1986,6 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "required_int64_group", requiredInt64Group));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "string_group", stringGroup));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "int64_group", int64Group));
-        
 
         if (requiredBooleanGroup != null)
         headerParams.add("required_boolean_group", apiClient.parameterToString(requiredBooleanGroup));
@@ -2618,7 +2615,7 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("multi".toUpperCase(Locale.ROOT)), "context", context));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "language", language));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "allowEmpty", allowEmpty));
-        
+
         final String[] localVarAccepts = { };
         final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
         final String[] localVarContentTypes = { };

samples/client/petstore/java/restclient-useSingleRequestParameter-static/src/main/java/org/openapitools/client/api/PetApi.java

@@ -229,7 +229,6 @@ public class PetApi {
         final MultiValueMap<String, String> cookieParams = new LinkedMultiValueMap<>();
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
-
         if (apiKey != null)
         headerParams.add("api_key", apiClient.parameterToString(apiKey));
         final String[] localVarAccepts = { };
@@ -309,7 +308,7 @@ public class PetApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "status", status));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };
@@ -390,7 +389,7 @@ public class PetApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "tags", tags));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };

samples/client/petstore/java/restclient-useSingleRequestParameter-static/src/main/java/org/openapitools/client/api/UserApi.java

@@ -527,7 +527,7 @@ public class UserApi {
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "username", username));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "password", password));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };

samples/client/petstore/java/restclient-useSingleRequestParameter/src/main/java/org/openapitools/client/ApiClient.java

@@ -13,6 +13,7 @@
 
 package org.openapitools.client;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
@@ -499,6 +500,36 @@ public class ApiClient extends JavaTimeFormatter {
         }
     }
 
+    /**
+    * Converts a parameter to a {@link MultiValueMap} containing Json-serialized values for use in REST requests
+    * @param collectionFormat The format to convert to
+    * @param name The name of the parameter
+    * @param value The parameter's value
+    * @return a Map containing the Json-serialized String value(s) of the input parameter
+    */
+    public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionFormat collectionFormat, String name, Object value) {
+        Collection<?> valueCollection;
+        if (value instanceof Collection) {
+            valueCollection = (Collection<?>) value;
+        } else {
+            try {
+                return parameterToMultiValueMap(collectionFormat, name, objectMapper.writeValueAsString(value));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        List<String> values = new ArrayList<>();
+        for(Object o : valueCollection) {
+            try {
+                values.add(objectMapper.writeValueAsString(o));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+    }
+
     /**
      * Converts a parameter to a {@link MultiValueMap} for use in REST requests
      * @param collectionFormat The format to convert to

samples/client/petstore/java/restclient-useSingleRequestParameter/src/main/java/org/openapitools/client/api/FakeApi.java

@@ -248,7 +248,6 @@ public class FakeApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query_1", query1));
-        
 
         if (header1 != null)
         headerParams.add("header_1", apiClient.parameterToString(header1));
@@ -939,7 +938,7 @@ public class FakeApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query", query));
-        
+
         final String[] localVarAccepts = { };
         final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
         final String[] localVarContentTypes = { 
@@ -1343,7 +1342,6 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_query_integer", enumQueryInteger));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_query_double", enumQueryDouble));
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("multi".toUpperCase(Locale.ROOT)), "enum_query_model_array", enumQueryModelArray));
-        
 
         if (enumHeaderStringArray != null)
         headerParams.add("enum_header_string_array", apiClient.parameterToString(enumHeaderStringArray));
@@ -1504,7 +1502,6 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "required_int64_group", requiredInt64Group));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "string_group", stringGroup));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "int64_group", int64Group));
-        
 
         if (requiredBooleanGroup != null)
         headerParams.add("required_boolean_group", apiClient.parameterToString(requiredBooleanGroup));
@@ -1991,7 +1988,7 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("multi".toUpperCase(Locale.ROOT)), "context", context));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "language", language));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "allowEmpty", allowEmpty));
-        
+
         final String[] localVarAccepts = { };
         final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
         final String[] localVarContentTypes = { };

samples/client/petstore/java/restclient-useSingleRequestParameter/src/main/java/org/openapitools/client/api/PetApi.java

@@ -185,7 +185,6 @@ public class PetApi {
         final MultiValueMap<String, String> cookieParams = new LinkedMultiValueMap<>();
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
-
         if (apiKey != null)
         headerParams.add("api_key", apiClient.parameterToString(apiKey));
         final String[] localVarAccepts = { };
@@ -265,7 +264,7 @@ public class PetApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "status", status));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };
@@ -346,7 +345,7 @@ public class PetApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "tags", tags));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };

samples/client/petstore/java/restclient-useSingleRequestParameter/src/main/java/org/openapitools/client/api/UserApi.java

@@ -483,7 +483,7 @@ public class UserApi {
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "username", username));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "password", password));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };

samples/client/petstore/java/restclient/src/main/java/org/openapitools/client/ApiClient.java

@@ -13,6 +13,7 @@
 
 package org.openapitools.client;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
@@ -499,6 +500,36 @@ public class ApiClient extends JavaTimeFormatter {
         }
     }
 
+    /**
+    * Converts a parameter to a {@link MultiValueMap} containing Json-serialized values for use in REST requests
+    * @param collectionFormat The format to convert to
+    * @param name The name of the parameter
+    * @param value The parameter's value
+    * @return a Map containing the Json-serialized String value(s) of the input parameter
+    */
+    public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionFormat collectionFormat, String name, Object value) {
+        Collection<?> valueCollection;
+        if (value instanceof Collection) {
+            valueCollection = (Collection<?>) value;
+        } else {
+            try {
+                return parameterToMultiValueMap(collectionFormat, name, objectMapper.writeValueAsString(value));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        List<String> values = new ArrayList<>();
+        for(Object o : valueCollection) {
+            try {
+                values.add(objectMapper.writeValueAsString(o));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+    }
+
     /**
      * Converts a parameter to a {@link MultiValueMap} for use in REST requests
      * @param collectionFormat The format to convert to

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

@@ -212,7 +212,6 @@ public class FakeApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query_1", query1));
-        
 
         if (header1 != null)
         headerParams.add("header_1", apiClient.parameterToString(header1));
@@ -867,7 +866,7 @@ public class FakeApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query", query));
-        
+
         final String[] localVarAccepts = { };
         final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
         final String[] localVarContentTypes = { 
@@ -1193,7 +1192,6 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_query_integer", enumQueryInteger));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_query_double", enumQueryDouble));
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("multi".toUpperCase(Locale.ROOT)), "enum_query_model_array", enumQueryModelArray));
-        
 
         if (enumHeaderStringArray != null)
         headerParams.add("enum_header_string_array", apiClient.parameterToString(enumHeaderStringArray));
@@ -1318,7 +1316,6 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "required_int64_group", requiredInt64Group));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "string_group", stringGroup));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "int64_group", int64Group));
-        
 
         if (requiredBooleanGroup != null)
         headerParams.add("required_boolean_group", apiClient.parameterToString(requiredBooleanGroup));
@@ -1733,7 +1730,7 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("multi".toUpperCase(Locale.ROOT)), "context", context));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "language", language));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "allowEmpty", allowEmpty));
-        
+
         final String[] localVarAccepts = { };
         final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
         final String[] localVarContentTypes = { };

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

@@ -146,7 +146,6 @@ public class PetApi {
         final MultiValueMap<String, String> cookieParams = new LinkedMultiValueMap<>();
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
-
         if (apiKey != null)
         headerParams.add("api_key", apiClient.parameterToString(apiKey));
         final String[] localVarAccepts = { };
@@ -226,7 +225,7 @@ public class PetApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "status", status));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };
@@ -307,7 +306,7 @@ public class PetApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "tags", tags));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };

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

@@ -442,7 +442,7 @@ public class UserApi {
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "username", username));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "password", password));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };

samples/client/petstore/java/webclient-jakarta/src/main/java/org/openapitools/client/ApiClient.java

@@ -13,6 +13,7 @@
 
 package org.openapitools.client;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
@@ -435,6 +436,36 @@ public class ApiClient extends JavaTimeFormatter {
         }
     }
 
+    /**
+    * Converts a parameter to a {@link MultiValueMap} containing Json-serialized values for use in REST requests
+    * @param collectionFormat The format to convert to
+    * @param name The name of the parameter
+    * @param value The parameter's value
+    * @return a Map containing the Json-serialized String value(s) of the input parameter
+    */
+    public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionFormat collectionFormat, String name, Object value) {
+        Collection<?> valueCollection;
+        if (value instanceof Collection) {
+            valueCollection = (Collection<?>) value;
+        } else {
+            try {
+                return parameterToMultiValueMap(collectionFormat, name, objectMapper.writeValueAsString(value));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        List<String> values = new ArrayList<>();
+        for(Object o : valueCollection) {
+            try {
+                values.add(objectMapper.writeValueAsString(o));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+    }
+
     /**
      * Converts a parameter to a {@link MultiValueMap} for use in REST requests
      * @param collectionFormat The format to convert to

samples/client/petstore/java/webclient-jakarta/src/main/java/org/openapitools/client/api/FakeApi.java

@@ -214,7 +214,6 @@ public class FakeApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query_1", query1));
-        
 
         if (header1 != null)
         headerParams.add("header_1", apiClient.parameterToString(header1));
@@ -869,7 +868,7 @@ public class FakeApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query", query));
-        
+
         final String[] localVarAccepts = { };
         final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
         final String[] localVarContentTypes = { 
@@ -1195,7 +1194,6 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_query_integer", enumQueryInteger));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_query_double", enumQueryDouble));
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("multi".toUpperCase(Locale.ROOT)), "enum_query_model_array", enumQueryModelArray));
-        
 
         if (enumHeaderStringArray != null)
         headerParams.add("enum_header_string_array", apiClient.parameterToString(enumHeaderStringArray));
@@ -1320,7 +1318,6 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "required_int64_group", requiredInt64Group));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "string_group", stringGroup));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "int64_group", int64Group));
-        
 
         if (requiredBooleanGroup != null)
         headerParams.add("required_boolean_group", apiClient.parameterToString(requiredBooleanGroup));
@@ -1735,7 +1732,7 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("multi".toUpperCase(Locale.ROOT)), "context", context));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "language", language));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "allowEmpty", allowEmpty));
-        
+
         final String[] localVarAccepts = { };
         final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
         final String[] localVarContentTypes = { };

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

@@ -148,7 +148,6 @@ public class PetApi {
         final MultiValueMap<String, String> cookieParams = new LinkedMultiValueMap<String, String>();
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
-
         if (apiKey != null)
         headerParams.add("api_key", apiClient.parameterToString(apiKey));
         final String[] localVarAccepts = { };
@@ -228,7 +227,7 @@ public class PetApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "status", status));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };
@@ -309,7 +308,7 @@ public class PetApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "tags", tags));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };

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

@@ -444,7 +444,7 @@ public class UserApi {
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "username", username));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "password", password));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };

samples/client/petstore/java/webclient-nullable-arrays/src/main/java/org/openapitools/client/ApiClient.java

@@ -13,6 +13,7 @@
 
 package org.openapitools.client;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
@@ -415,6 +416,36 @@ public class ApiClient extends JavaTimeFormatter {
         }
     }
 
+    /**
+    * Converts a parameter to a {@link MultiValueMap} containing Json-serialized values for use in REST requests
+    * @param collectionFormat The format to convert to
+    * @param name The name of the parameter
+    * @param value The parameter's value
+    * @return a Map containing the Json-serialized String value(s) of the input parameter
+    */
+    public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionFormat collectionFormat, String name, Object value) {
+        Collection<?> valueCollection;
+        if (value instanceof Collection) {
+            valueCollection = (Collection<?>) value;
+        } else {
+            try {
+                return parameterToMultiValueMap(collectionFormat, name, objectMapper.writeValueAsString(value));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        List<String> values = new ArrayList<>();
+        for(Object o : valueCollection) {
+            try {
+                values.add(objectMapper.writeValueAsString(o));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+    }
+
     /**
      * Converts a parameter to a {@link MultiValueMap} for use in REST requests
      * @param collectionFormat The format to convert to

samples/client/petstore/java/webclient-swagger2/src/main/java/org/openapitools/client/ApiClient.java

@@ -13,6 +13,7 @@
 
 package org.openapitools.client;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
@@ -435,6 +436,36 @@ public class ApiClient extends JavaTimeFormatter {
         }
     }
 
+    /**
+    * Converts a parameter to a {@link MultiValueMap} containing Json-serialized values for use in REST requests
+    * @param collectionFormat The format to convert to
+    * @param name The name of the parameter
+    * @param value The parameter's value
+    * @return a Map containing the Json-serialized String value(s) of the input parameter
+    */
+    public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionFormat collectionFormat, String name, Object value) {
+        Collection<?> valueCollection;
+        if (value instanceof Collection) {
+            valueCollection = (Collection<?>) value;
+        } else {
+            try {
+                return parameterToMultiValueMap(collectionFormat, name, objectMapper.writeValueAsString(value));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        List<String> values = new ArrayList<>();
+        for(Object o : valueCollection) {
+            try {
+                values.add(objectMapper.writeValueAsString(o));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+    }
+
     /**
      * Converts a parameter to a {@link MultiValueMap} for use in REST requests
      * @param collectionFormat The format to convert to

samples/client/petstore/java/webclient-swagger2/src/main/java/org/openapitools/client/api/FakeApi.java

@@ -214,7 +214,6 @@ public class FakeApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query_1", query1));
-        
 
         if (header1 != null)
         headerParams.add("header_1", apiClient.parameterToString(header1));
@@ -869,7 +868,7 @@ public class FakeApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query", query));
-        
+
         final String[] localVarAccepts = { };
         final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
         final String[] localVarContentTypes = { 
@@ -1195,7 +1194,6 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_query_integer", enumQueryInteger));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_query_double", enumQueryDouble));
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("multi".toUpperCase(Locale.ROOT)), "enum_query_model_array", enumQueryModelArray));
-        
 
         if (enumHeaderStringArray != null)
         headerParams.add("enum_header_string_array", apiClient.parameterToString(enumHeaderStringArray));
@@ -1320,7 +1318,6 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "required_int64_group", requiredInt64Group));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "string_group", stringGroup));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "int64_group", int64Group));
-        
 
         if (requiredBooleanGroup != null)
         headerParams.add("required_boolean_group", apiClient.parameterToString(requiredBooleanGroup));
@@ -1735,7 +1732,7 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("multi".toUpperCase(Locale.ROOT)), "context", context));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "language", language));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "allowEmpty", allowEmpty));
-        
+
         final String[] localVarAccepts = { };
         final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
         final String[] localVarContentTypes = { };

samples/client/petstore/java/webclient-swagger2/src/main/java/org/openapitools/client/api/PetApi.java

@@ -148,7 +148,6 @@ public class PetApi {
         final MultiValueMap<String, String> cookieParams = new LinkedMultiValueMap<String, String>();
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
-
         if (apiKey != null)
         headerParams.add("api_key", apiClient.parameterToString(apiKey));
         final String[] localVarAccepts = { };
@@ -228,7 +227,7 @@ public class PetApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "status", status));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };
@@ -309,7 +308,7 @@ public class PetApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "tags", tags));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };

samples/client/petstore/java/webclient-swagger2/src/main/java/org/openapitools/client/api/UserApi.java

@@ -444,7 +444,7 @@ public class UserApi {
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "username", username));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "password", password));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };

samples/client/petstore/java/webclient-useSingleRequestParameter/src/main/java/org/openapitools/client/ApiClient.java

@@ -13,6 +13,7 @@
 
 package org.openapitools.client;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
@@ -435,6 +436,36 @@ public class ApiClient extends JavaTimeFormatter {
         }
     }
 
+    /**
+    * Converts a parameter to a {@link MultiValueMap} containing Json-serialized values for use in REST requests
+    * @param collectionFormat The format to convert to
+    * @param name The name of the parameter
+    * @param value The parameter's value
+    * @return a Map containing the Json-serialized String value(s) of the input parameter
+    */
+    public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionFormat collectionFormat, String name, Object value) {
+        Collection<?> valueCollection;
+        if (value instanceof Collection) {
+            valueCollection = (Collection<?>) value;
+        } else {
+            try {
+                return parameterToMultiValueMap(collectionFormat, name, objectMapper.writeValueAsString(value));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        List<String> values = new ArrayList<>();
+        for(Object o : valueCollection) {
+            try {
+                values.add(objectMapper.writeValueAsString(o));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+    }
+
     /**
      * Converts a parameter to a {@link MultiValueMap} for use in REST requests
      * @param collectionFormat The format to convert to

samples/client/petstore/java/webclient-useSingleRequestParameter/src/main/java/org/openapitools/client/api/FakeApi.java

@@ -306,7 +306,6 @@ public class FakeApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query_1", query1));
-        
 
         if (header1 != null)
         headerParams.add("header_1", apiClient.parameterToString(header1));
@@ -1042,7 +1041,7 @@ public class FakeApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query", query));
-        
+
         final String[] localVarAccepts = { };
         final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
         final String[] localVarContentTypes = { 
@@ -1745,7 +1744,6 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_query_integer", enumQueryInteger));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_query_double", enumQueryDouble));
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("multi".toUpperCase(Locale.ROOT)), "enum_query_model_array", enumQueryModelArray));
-        
 
         if (enumHeaderStringArray != null)
         headerParams.add("enum_header_string_array", apiClient.parameterToString(enumHeaderStringArray));
@@ -1995,7 +1993,6 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "required_int64_group", requiredInt64Group));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "string_group", stringGroup));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "int64_group", int64Group));
-        
 
         if (requiredBooleanGroup != null)
         headerParams.add("required_boolean_group", apiClient.parameterToString(requiredBooleanGroup));
@@ -2627,7 +2624,7 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("multi".toUpperCase(Locale.ROOT)), "context", context));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "language", language));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "allowEmpty", allowEmpty));
-        
+
         final String[] localVarAccepts = { };
         final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
         final String[] localVarContentTypes = { };

samples/client/petstore/java/webclient-useSingleRequestParameter/src/main/java/org/openapitools/client/api/PetApi.java

@@ -232,7 +232,6 @@ public class PetApi {
         final MultiValueMap<String, String> cookieParams = new LinkedMultiValueMap<String, String>();
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
-
         if (apiKey != null)
         headerParams.add("api_key", apiClient.parameterToString(apiKey));
         final String[] localVarAccepts = { };
@@ -312,7 +311,7 @@ public class PetApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "status", status));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };
@@ -393,7 +392,7 @@ public class PetApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "tags", tags));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };

samples/client/petstore/java/webclient-useSingleRequestParameter/src/main/java/org/openapitools/client/api/UserApi.java

@@ -530,7 +530,7 @@ public class UserApi {
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "username", username));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "password", password));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };

samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/ApiClient.java

@@ -13,6 +13,7 @@
 
 package org.openapitools.client;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
@@ -435,6 +436,36 @@ public class ApiClient extends JavaTimeFormatter {
         }
     }
 
+    /**
+    * Converts a parameter to a {@link MultiValueMap} containing Json-serialized values for use in REST requests
+    * @param collectionFormat The format to convert to
+    * @param name The name of the parameter
+    * @param value The parameter's value
+    * @return a Map containing the Json-serialized String value(s) of the input parameter
+    */
+    public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionFormat collectionFormat, String name, Object value) {
+        Collection<?> valueCollection;
+        if (value instanceof Collection) {
+            valueCollection = (Collection<?>) value;
+        } else {
+            try {
+                return parameterToMultiValueMap(collectionFormat, name, objectMapper.writeValueAsString(value));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        List<String> values = new ArrayList<>();
+        for(Object o : valueCollection) {
+            try {
+                values.add(objectMapper.writeValueAsString(o));
+            } catch (JsonProcessingException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+    }
+
     /**
      * Converts a parameter to a {@link MultiValueMap} for use in REST requests
      * @param collectionFormat The format to convert to

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

@@ -214,7 +214,6 @@ public class FakeApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query_1", query1));
-        
 
         if (header1 != null)
         headerParams.add("header_1", apiClient.parameterToString(header1));
@@ -869,7 +868,7 @@ public class FakeApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "query", query));
-        
+
         final String[] localVarAccepts = { };
         final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
         final String[] localVarContentTypes = { 
@@ -1195,7 +1194,6 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_query_integer", enumQueryInteger));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "enum_query_double", enumQueryDouble));
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("multi".toUpperCase(Locale.ROOT)), "enum_query_model_array", enumQueryModelArray));
-        
 
         if (enumHeaderStringArray != null)
         headerParams.add("enum_header_string_array", apiClient.parameterToString(enumHeaderStringArray));
@@ -1320,7 +1318,6 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "required_int64_group", requiredInt64Group));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "string_group", stringGroup));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "int64_group", int64Group));
-        
 
         if (requiredBooleanGroup != null)
         headerParams.add("required_boolean_group", apiClient.parameterToString(requiredBooleanGroup));
@@ -1735,7 +1732,7 @@ public class FakeApi {
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("multi".toUpperCase(Locale.ROOT)), "context", context));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "language", language));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "allowEmpty", allowEmpty));
-        
+
         final String[] localVarAccepts = { };
         final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
         final String[] localVarContentTypes = { };

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

@@ -148,7 +148,6 @@ public class PetApi {
         final MultiValueMap<String, String> cookieParams = new LinkedMultiValueMap<String, String>();
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
-
         if (apiKey != null)
         headerParams.add("api_key", apiClient.parameterToString(apiKey));
         final String[] localVarAccepts = { };
@@ -228,7 +227,7 @@ public class PetApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "status", status));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };
@@ -309,7 +308,7 @@ public class PetApi {
         final MultiValueMap<String, Object> formParams = new LinkedMultiValueMap<String, Object>();
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf("csv".toUpperCase(Locale.ROOT)), "tags", tags));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };

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

@@ -444,7 +444,7 @@ public class UserApi {
 
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "username", username));
         queryParams.putAll(apiClient.parameterToMultiValueMap(null, "password", password));
-        
+
         final String[] localVarAccepts = { 
             "application/xml", "application/json"
         };