[Java][RestTemplate][WebClient] Incorrect handling of free form query parameters

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

@@ -479,6 +479,14 @@ public class ApiClient{{#jsr310}} extends JavaTimeFormatter{{/jsr310}} {
             collectionFormat = CollectionFormat.CSV;
         }
 
+        if (value instanceof Map) {
+            final Map<String, Object> valuesMap = (Map<String, Object>) value;
+            for (final Entry<String, Object> entry : valuesMap.entrySet()) {
+                params.add(entry.getKey(), parameterToString(entry.getValue()));
+            }
+            return params;
+        }
+
         Collection<?> valueCollection = null;
         if (value instanceof Collection) {
             valueCollection = (Collection<?>) value;

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

@@ -457,6 +457,14 @@ public class ApiClient{{#jsr310}} extends JavaTimeFormatter{{/jsr310}} {
             collectionFormat = CollectionFormat.CSV;
         }
 
+        if (value instanceof Map) {
+            final Map<String, Object> valuesMap = (Map<String, Object>) value;
+            for (final Entry<String, Object> entry : valuesMap.entrySet()) {
+                params.add(entry.getKey(), parameterToString(entry.getValue()));
+            }
+            return params;
+        }
+
         Collection<?> valueCollection = null;
         if (value instanceof Collection) {
             valueCollection = (Collection<?>) value;

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

@@ -1164,4 +1164,62 @@ public void testWebClientWithUseAbstractionForFiles() throws IOException {
                 "formParams.add(\"file\", file);"
         );
     }
+
+    /**
+     * See https://github.com/OpenAPITools/openapi-generator/issues/8352
+     */
+    @Test
+    public void testRestTemplateWithFreeFormInQueryParameters() throws IOException {
+        final Map<String, Object> properties = new HashMap<>();
+        properties.put(AbstractJavaCodegen.JAVA8_MODE, true);
+        properties.put(CodegenConstants.API_PACKAGE, "xyz.abcdef.api");
+
+        final File output = Files.createTempDirectory("test")
+                .toFile();
+        output.deleteOnExit();
+
+        final CodegenConfigurator configurator = new CodegenConfigurator().setGeneratorName("java")
+                .setLibrary(JavaClientCodegen.RESTTEMPLATE)
+                .setAdditionalProperties(properties)
+                .setInputSpec("src/test/resources/3_0/issue8352.yaml")
+                .setOutputDir(output.getAbsolutePath()
+                        .replace("\\", "/"));
+
+        final DefaultGenerator generator = new DefaultGenerator();
+        final List<File> files = generator.opts(configurator.toClientOptInput())
+                .generate();
+        files.forEach(File::deleteOnExit);
+
+        final Path defaultApi = Paths.get(output + "/src/main/java/xyz/abcdef/ApiClient.java");
+        TestUtils.assertFileContains(defaultApi, "value instanceof Map");
+    }
+
+    /**
+     * See https://github.com/OpenAPITools/openapi-generator/issues/8352
+     */
+    @Test
+    public void testWebClientWithFreeFormInQueryParameters() throws IOException {
+        final Map<String, Object> properties = new HashMap<>();
+        properties.put(AbstractJavaCodegen.JAVA8_MODE, true);
+        properties.put(CodegenConstants.API_PACKAGE, "xyz.abcdef.api");
+
+        final File output = Files.createTempDirectory("test")
+                .toFile();
+        output.deleteOnExit();
+
+        final CodegenConfigurator configurator = new CodegenConfigurator().setGeneratorName("java")
+                .setLibrary(JavaClientCodegen.WEBCLIENT)
+                .setAdditionalProperties(properties)
+                .setInputSpec("src/test/resources/3_0/issue8352.yaml")
+                .setOutputDir(output.getAbsolutePath()
+                        .replace("\\", "/"));
+
+        final DefaultGenerator generator = new DefaultGenerator();
+        final List<File> files = generator.opts(configurator.toClientOptInput())
+                .generate();
+        files.forEach(File::deleteOnExit);
+
+        final Path defaultApi = Paths.get(output + "/src/main/java/xyz/abcdef/ApiClient.java");
+        TestUtils.assertFileContains(defaultApi, "value instanceof Map");
+    }
 }

modules/openapi-generator/src/test/resources/3_0/issue8352.yaml

@@ -0,0 +1,18 @@
+openapi: 3.0.0
+info:
+  title: test handle of free form query parameters
+  version: 0.0.1
+servers:
+  - url: "http://localhost"
+paths:
+  /some/endpoint:
+    get:
+      parameters:
+        - in: "query"
+          name: "free-form"
+          schema:
+            type: "object"
+          style: "form"
+      responses:
+        200:
+          description: "test"

samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/ApiClient.java

@@ -435,6 +435,14 @@ public MultiValueMap<String, String> parameterToMultiValueMap(CollectionFormat c
             collectionFormat = CollectionFormat.CSV;
         }
 
+        if (value instanceof Map) {
+            final Map<String, Object> valuesMap = (Map<String, Object>) value;
+            for (final Entry<String, Object> entry : valuesMap.entrySet()) {
+                params.add(entry.getKey(), parameterToString(entry.getValue()));
+            }
+            return params;
+        }
+
         Collection<?> valueCollection = null;
         if (value instanceof Collection) {
             valueCollection = (Collection<?>) value;

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

@@ -430,6 +430,14 @@ public MultiValueMap<String, String> parameterToMultiValueMap(CollectionFormat c
             collectionFormat = CollectionFormat.CSV;
         }
 
+        if (value instanceof Map) {
+            final Map<String, Object> valuesMap = (Map<String, Object>) value;
+            for (final Entry<String, Object> entry : valuesMap.entrySet()) {
+                params.add(entry.getKey(), parameterToString(entry.getValue()));
+            }
+            return params;
+        }
+
         Collection<?> valueCollection = null;
         if (value instanceof Collection) {
             valueCollection = (Collection<?>) value;

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

@@ -423,6 +423,14 @@ public MultiValueMap<String, String> parameterToMultiValueMap(CollectionFormat c
             collectionFormat = CollectionFormat.CSV;
         }
 
+        if (value instanceof Map) {
+            final Map<String, Object> valuesMap = (Map<String, Object>) value;
+            for (final Entry<String, Object> entry : valuesMap.entrySet()) {
+                params.add(entry.getKey(), parameterToString(entry.getValue()));
+            }
+            return params;
+        }
+
         Collection<?> valueCollection = null;
         if (value instanceof Collection) {
             valueCollection = (Collection<?>) value;

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

@@ -444,6 +444,14 @@ public MultiValueMap<String, String> parameterToMultiValueMap(CollectionFormat c
             collectionFormat = CollectionFormat.CSV;
         }
 
+        if (value instanceof Map) {
+            final Map<String, Object> valuesMap = (Map<String, Object>) value;
+            for (final Entry<String, Object> entry : valuesMap.entrySet()) {
+                params.add(entry.getKey(), parameterToString(entry.getValue()));
+            }
+            return params;
+        }
+
         Collection<?> valueCollection = null;
         if (value instanceof Collection) {
             valueCollection = (Collection<?>) value;