[JAVA-SPRING] Convert byte[] to String for operation params [QueryParam; PathParam; HeaderParam; CookieParam; FormParam]

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJavaCodegen.java

@@ -290,6 +290,7 @@ public AbstractJavaCodegen() {
         typeMapping.put("date", "Date");
         typeMapping.put("file", "File");
         typeMapping.put("AnyType", "Object");
+        typeMapping.put("ByteArray", "byte[]");
 
         importMapping.put("BigDecimal", "java.math.BigDecimal");
         importMapping.put("UUID", "java.util.UUID");

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/SpringCodegen.java

@@ -798,6 +798,7 @@ public void setIsVoid(boolean isVoid) {
 
                 prepareVersioningParameters(ops);
                 handleImplicitHeaders(operation);
+                convertByteArrayParamsToStringType(operation);
             }
             // The tag for the controller is the first tag of the first operation
             final CodegenOperation firstOperation = ops.get(0);
@@ -813,6 +814,26 @@ public void setIsVoid(boolean isVoid) {
         return objs;
     }
 
+    /**
+     * Converts parameters of type {@code byte[]} (i.e., OpenAPI {@code type: string, format: byte}) to {@code String}.
+     * <p>
+     * In OpenAPI, {@code type: string, format: byte} is a base64-encoded string. However, Spring does not automatically
+     * decode base64-encoded request parameters into {@code byte[]} for query, path, header, cookie, or form parameters.
+     * Therefore, these parameters are mapped to {@code String} to avoid incorrect type handling and to ensure the
+     * application receives the raw base64 string as provided by the client.
+     * </p>
+     *
+     * @param operation the codegen operation whose parameters will be checked and converted if necessary
+     **/
+    private void convertByteArrayParamsToStringType(CodegenOperation operation) {
+        var convertedParams = operation.allParams.stream()
+                .filter(CodegenParameter::getIsByteArray)
+                .filter(param -> param.isQueryParam || param.isPathParam || param.isHeaderParam || param.isCookieParam || param.isFormParam)
+                .peek(param -> param.dataType = "String")
+                .collect(Collectors.toList());
+        LOGGER.info("Converted parameters {} from byte[] to String in operation {}", convertedParams.stream().map(param -> param.paramName), operation.operationId);
+    }
+
     private interface DataTypeAssigner {
         void setReturnType(String returnType);
 

modules/openapi-generator/src/main/resources/JavaSpring/cookieParams.mustache

@@ -1 +1 @@
-{{#isCookieParam}}{{#useBeanValidation}}{{>beanValidationQueryParams}}{{/useBeanValidation}}{{>paramDoc}} @CookieValue(name = "{{baseName}}"{{^required}}, required = false{{/required}}{{#defaultValue}}, defaultValue = "{{{.}}}"{{/defaultValue}}){{>dateTimeParam}} {{>nullableAnnotation}}{{>optionalDataType}} {{paramName}}{{/isCookieParam}}
+{{#isCookieParam}}{{#useBeanValidation}}{{>beanValidationQueryParams}}{{/useBeanValidation}}{{>paramDoc}} @CookieValue(name = "{{baseName}}"{{^required}}, required = false{{/required}}{{#defaultValue}}, defaultValue = "{{{.}}}"{{/defaultValue}}){{>dateTimeParam}} {{>nullableAnnotation}}{{>optionalDataType}} {{paramName}}{{#isByteArray}} /* base64 encoded binary */{{/isByteArray}}{{/isCookieParam}}

modules/openapi-generator/src/main/resources/JavaSpring/formParams.mustache

@@ -1 +1 @@
-{{#isFormParam}}{{^isFile}}{{>paramDoc}}{{#useBeanValidation}} {{>beanValidationBodyParams}}@Valid{{/useBeanValidation}} {{#isModel}}@RequestPart{{/isModel}}{{^isModel}}{{#isArray}}@RequestPart{{/isArray}}{{^isArray}}{{#reactive}}@RequestPart{{/reactive}}{{^reactive}}@RequestParam{{/reactive}}{{/isArray}}{{/isModel}}(value = "{{baseName}}"{{#required}}, required = true{{/required}}{{^required}}, required = false{{/required}}){{>dateTimeParam}} {{^required}}{{#useOptional}}Optional<{{/useOptional}}{{/required}}{{{dataType}}}{{^required}}{{#useOptional}}>{{/useOptional}}{{/required}} {{paramName}}{{/isFile}}{{#isFile}}{{>paramDoc}} @RequestPart(value = "{{baseName}}"{{#required}}, required = true{{/required}}{{^required}}, required = false{{/required}}) {{#reactive}}{{#isArray}}Flux<{{/isArray}}Part{{#isArray}}>{{/isArray}}{{/reactive}}{{^reactive}}{{#isArray}}List<{{/isArray}}MultipartFile{{#isArray}}>{{/isArray}}{{/reactive}} {{paramName}}{{/isFile}}{{/isFormParam}}
+{{#isFormParam}}{{^isFile}}{{>paramDoc}}{{#useBeanValidation}} {{>beanValidationBodyParams}}@Valid{{/useBeanValidation}} {{#isModel}}@RequestPart{{/isModel}}{{^isModel}}{{#isArray}}@RequestPart{{/isArray}}{{^isArray}}{{#reactive}}@RequestPart{{/reactive}}{{^reactive}}@RequestParam{{/reactive}}{{/isArray}}{{/isModel}}(value = "{{baseName}}"{{#required}}, required = true{{/required}}{{^required}}, required = false{{/required}}){{>dateTimeParam}} {{^required}}{{#useOptional}}Optional<{{/useOptional}}{{/required}}{{{dataType}}}{{^required}}{{#useOptional}}>{{/useOptional}}{{/required}} {{paramName}}{{/isFile}}{{#isByteArray}} /* base64 encoded binary */{{/isByteArray}}{{#isFile}}{{>paramDoc}} @RequestPart(value = "{{baseName}}"{{#required}}, required = true{{/required}}{{^required}}, required = false{{/required}}) {{#reactive}}{{#isArray}}Flux<{{/isArray}}Part{{#isArray}}>{{/isArray}}{{/reactive}}{{^reactive}}{{#isArray}}List<{{/isArray}}MultipartFile{{#isArray}}>{{/isArray}}{{/reactive}} {{paramName}}{{/isFile}}{{/isFormParam}}

modules/openapi-generator/src/main/resources/JavaSpring/headerParams.mustache

@@ -1 +1 @@
-{{#isHeaderParam}}{{#vendorExtensions.x-field-extra-annotation}}{{{.}}} {{/vendorExtensions.x-field-extra-annotation}}{{#useBeanValidation}}{{>beanValidationQueryParams}}{{/useBeanValidation}}{{>paramDoc}} @RequestHeader(value = "{{baseName}}", required = {{#required}}true{{/required}}{{^required}}false{{/required}}{{#defaultValue}}, defaultValue = "{{{.}}}"{{/defaultValue}}){{>dateTimeParam}} {{>nullableAnnotation}}{{>optionalDataType}} {{paramName}}{{/isHeaderParam}}
+{{#isHeaderParam}}{{#vendorExtensions.x-field-extra-annotation}}{{{.}}} {{/vendorExtensions.x-field-extra-annotation}}{{#useBeanValidation}}{{>beanValidationQueryParams}}{{/useBeanValidation}}{{>paramDoc}} @RequestHeader(value = "{{baseName}}", required = {{#required}}true{{/required}}{{^required}}false{{/required}}{{#defaultValue}}, defaultValue = "{{{.}}}"{{/defaultValue}}){{>dateTimeParam}} {{>nullableAnnotation}}{{>optionalDataType}} {{paramName}}{{#isByteArray}} /* base64 encoded binary */{{/isByteArray}}{{/isHeaderParam}}

modules/openapi-generator/src/main/resources/JavaSpring/pathParams.mustache

@@ -1 +1 @@
-{{#isPathParam}}{{#vendorExtensions.x-field-extra-annotation}}{{{.}}} {{/vendorExtensions.x-field-extra-annotation}}{{#useBeanValidation}}{{>beanValidationPathParams}}{{/useBeanValidation}}{{>paramDoc}} @PathVariable("{{baseName}}"){{>dateTimeParam}}{{#isDeprecated}} @Deprecated{{/isDeprecated}} {{>optionalDataType}} {{paramName}}{{/isPathParam}}
+{{#isPathParam}}{{#vendorExtensions.x-field-extra-annotation}}{{{.}}} {{/vendorExtensions.x-field-extra-annotation}}{{#useBeanValidation}}{{>beanValidationPathParams}}{{/useBeanValidation}}{{>paramDoc}} @PathVariable("{{baseName}}"){{>dateTimeParam}}{{#isDeprecated}} @Deprecated{{/isDeprecated}} {{>optionalDataType}} {{paramName}}{{#isByteArray}} /* base64 encoded binary */{{/isByteArray}}{{/isPathParam}}

modules/openapi-generator/src/main/resources/JavaSpring/queryParams.mustache

@@ -1 +1 @@
-{{#isQueryParam}}{{#vendorExtensions.x-field-extra-annotation}}{{{.}}} {{/vendorExtensions.x-field-extra-annotation}}{{#useBeanValidation}}{{>beanValidationQueryParams}}{{/useBeanValidation}}{{>paramDoc}}{{#useBeanValidation}} @Valid{{/useBeanValidation}}{{^isModel}} @RequestParam(value = {{#isMap}}""{{/isMap}}{{^isMap}}"{{baseName}}"{{/isMap}}{{#required}}, required = true{{/required}}{{^required}}, required = false{{/required}}{{#defaultValue}}, defaultValue = "{{{.}}}"{{/defaultValue}}){{/isModel}}{{>dateTimeParam}}{{#isDeprecated}} @Deprecated{{/isDeprecated}} {{>nullableAnnotation}}{{>optionalDataType}} {{paramName}}{{/isQueryParam}}
+{{#isQueryParam}}{{#vendorExtensions.x-field-extra-annotation}}{{{.}}} {{/vendorExtensions.x-field-extra-annotation}}{{#useBeanValidation}}{{>beanValidationQueryParams}}{{/useBeanValidation}}{{>paramDoc}}{{#useBeanValidation}} @Valid{{/useBeanValidation}}{{^isModel}} @RequestParam(value = {{#isMap}}""{{/isMap}}{{^isMap}}"{{baseName}}"{{/isMap}}{{#required}}, required = true{{/required}}{{^required}}, required = false{{/required}}{{#defaultValue}}, defaultValue = "{{{.}}}"{{/defaultValue}}){{/isModel}}{{>dateTimeParam}}{{#isDeprecated}} @Deprecated{{/isDeprecated}} {{>nullableAnnotation}}{{>optionalDataType}} {{paramName}}{{#isByteArray}} /* base64 encoded binary */{{/isByteArray}}{{/isQueryParam}}

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

@@ -26,6 +26,20 @@ public PropertyAssert withType(final String expectedType) {
         return this;
     }
 
+    public PropertyAssert isArray() {
+        Assertions.assertThat(actual.getCommonType().isArrayType())
+                .withFailMessage("Expected property %s to be array, but it was NOT", actual.getVariable(0).getNameAsString())
+                .isEqualTo(true);
+        return this;
+    }
+
+    public PropertyAssert isNotArray() {
+        Assertions.assertThat(actual.getCommonType().isArrayType())
+                .withFailMessage("Expected property %s NOT to be array, but it was", actual.getVariable(0).getNameAsString())
+                .isEqualTo(false);
+        return this;
+    }
+
     public PropertyAnnotationsAssert assertPropertyAnnotations() {
         return new PropertyAnnotationsAssert(this, actual.getAnnotations());
     }

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

@@ -864,6 +864,92 @@ public void testSchemaImplements() throws IOException {
                 .implementsInterfaces(fooInterface, fooAnotherInterface);
     }
 
+
+    @Test
+    public void shouldHandleFormatByteCorrectlyForAllApiParametersAndProperties() throws IOException {
+        final SpringCodegen codegen = new SpringCodegen();
+
+        final Map<String, File> files = generateFiles(codegen, "src/test/resources/3_0/spring/byte-format-edge-cases.yaml");
+        // Query parameters: both plain text and Base64-encoded fields are mapped to String
+        JavaFileAssert.assertThat(files.get("QueryApi.java"))
+                .assertMethod("queryParams")
+                .assertParameter("plain")
+                .hasType("String");   // plain query param → always String
+        JavaFileAssert.assertThat(files.get("QueryApi.java"))
+                .assertMethod("queryParams")
+                .assertParameter("_byte")
+                .hasType("String");   // Base64 query param → String (manual decoding needed)
+
+        // Path parameters: same behavior as query params
+        JavaFileAssert.assertThat(files.get("PathApi.java"))
+                .assertMethod("pathParams")
+                .assertParameter("plain")
+                .hasType("String");   // path param → String
+        JavaFileAssert.assertThat(files.get("PathApi.java"))
+                .assertMethod("pathParams")
+                .assertParameter("_byte")
+                .hasType("String");   // Base64 path param → String
+
+        // Header parameters: always String
+        JavaFileAssert.assertThat(files.get("HeaderApi.java"))
+                .assertMethod("headerParams")
+                .assertParameter("xPlain")
+                .hasType("String");   // header → String
+        JavaFileAssert.assertThat(files.get("HeaderApi.java"))
+                .assertMethod("headerParams")
+                .assertParameter("xByte")
+                .hasType("String");   // Base64 header → String
+
+        // Cookie parameters: always String
+        JavaFileAssert.assertThat(files.get("CookieApi.java"))
+                .assertMethod("cookieParams")
+                .assertParameter("plain")
+                .hasType("String");   // cookie → String
+        JavaFileAssert.assertThat(files.get("CookieApi.java"))
+                .assertMethod("cookieParams")
+                .assertParameter("_byte")
+                .hasType("String");   // Base64 cookie → String
+
+        // Form fields: text fields → String
+        JavaFileAssert.assertThat(files.get("FormApi.java"))
+                .assertMethod("formParams")
+                .assertParameter("plain")
+                .hasType("String");   // form field → String
+        JavaFileAssert.assertThat(files.get("FormApi.java"))
+                .assertMethod("formParams")
+                .assertParameter("_byte")
+                .hasType("String");   // Base64 form field → String
+
+        // Multipart fields: text fields → String, files → MultipartFile
+        JavaFileAssert.assertThat(files.get("MultipartApi.java"))
+                .assertMethod("multipartParams")
+                .assertParameter("plain")
+                .hasType("String");   // multipart text field → String
+        JavaFileAssert.assertThat(files.get("MultipartApi.java"))
+                .assertMethod("multipartParams")
+                .assertParameter("_byte")
+                .hasType("String");   // Base64 multipart text → String
+        JavaFileAssert.assertThat(files.get("MultipartApi.java"))
+                .assertMethod("multipartParams")
+                .assertParameter("file")
+                .hasType("MultipartFile");   // binary file upload → MultipartFile
+
+        // Form request DTO: JSON or form object mapping
+        JavaFileAssert.assertThat(files.get("FormParamsRequest.java"))
+                .assertProperty("plain")
+                .withType("String");  // text property → String
+        JavaFileAssert.assertThat(files.get("FormParamsRequest.java"))
+                .assertProperty("_byte")
+                .isArray()
+                .withType("byte");  // Base64 property in DTO → auto-decoded to byte[]
+
+        // Binary request body: bound as Resource for streaming
+        JavaFileAssert.assertThat(files.get("BinaryBodyApi.java"))
+                .assertMethod("binaryBody")
+                .assertParameter("body")
+                .hasType("org.springframework.core.io.Resource");  // raw binary body → Resource (streamable)
+    }
+
     @Test
     public void shouldAddParameterWithInHeaderWhenImplicitHeadersIsTrue_issue14418() throws IOException {
         File output = Files.createTempDirectory("test").toFile().getCanonicalFile();

modules/openapi-generator/src/test/resources/3_0/spring/byte-format-edge-cases.yaml

@@ -0,0 +1,171 @@
+openapi: 3.0.3
+info:
+  title: Byte Format Edge Cases
+  version: 1.0.0
+
+paths:
+  /queryfdsfsd:
+    get:
+      operationId: queryParamsfdsfsfdsfs
+      summary: Query parametersfsdaf
+      parameters:
+        - name: plain
+          in: query
+          schema:
+            type: string
+
+      responses:
+        '204':
+          description: No content
+
+  /query:
+    get:
+      operationId: queryParams
+      summary: Query parameters
+      parameters:
+        - name: plain
+          in: query
+          schema:
+            type: string
+        - name: byte
+          in: query
+          schema:
+            type: string
+            format: byte
+      responses:
+        '204':
+          description: No content
+
+  /path/{plain}/{byte}:
+    get:
+      operationId: pathParams
+      summary: Path parameters
+      parameters:
+        - name: plain
+          in: path
+          required: true
+          schema:
+            type: string
+        - name: byte
+          in: path
+          required: true
+          schema:
+            type: string
+            format: byte
+      responses:
+        '204':
+          description: No content
+
+  /header:
+    get:
+      operationId: headerParams
+      summary: Header parameters
+      parameters:
+        - name: X-Plain
+          in: header
+          schema:
+            type: string
+        - name: X-Byte
+          in: header
+          schema:
+            type: string
+            format: byte
+      responses:
+        '204':
+          description: No content
+
+  /cookie:
+    get:
+      operationId: cookieParams
+      summary: Cookie parameters
+      parameters:
+        - name: plain
+          in: cookie
+          schema:
+            type: string
+        - name: byte
+          in: cookie
+          schema:
+            type: string
+            format: byte
+      responses:
+        '204':
+          description: No content
+
+  /form:
+    post:
+      operationId: formParams
+      summary: application/x-www-form-urlencoded
+      requestBody:
+        required: true
+        content:
+          application/x-www-form-urlencoded:
+            schema:
+              type: object
+              properties:
+                plain:
+                  type: string
+                byte:
+                  type: string
+                  format: byte
+      responses:
+        '204':
+          description: No content
+
+  /multipart:
+    post:
+      operationId: multipartParams
+      summary: multipart/form-data
+      requestBody:
+        required: true
+        content:
+          multipart/form-data:
+            schema:
+              type: object
+              properties:
+                plain:
+                  type: string
+                byte:
+                  type: string
+                  format: byte
+                file:
+                  type: string
+                  format: binary
+      responses:
+        '204':
+          description: No content
+
+  /json-body:
+    post:
+      operationId: jsonBody
+      summary: JSON request body
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              type: object
+              properties:
+                plain:
+                  type: string
+                byte:
+                  type: string
+                  format: byte
+      responses:
+        '204':
+          description: No content
+
+  /binary-body:
+    post:
+      operationId: binaryBody
+      summary: Raw binary body
+      requestBody:
+        required: true
+        content:
+          application/octet-stream:
+            schema:
+              type: string
+              format: binary
+      responses:
+        '204':
+          description: No content

samples/client/petstore/spring-http-interface-noResponseEntity/src/main/java/org/openapitools/api/FakeApi.java

@@ -216,7 +216,7 @@ void testEndpointParameters(
          @RequestParam(value = "number", required = true) BigDecimal number,
          @RequestParam(value = "double", required = true) Double _double,
          @RequestParam(value = "pattern_without_delimiter", required = true) String patternWithoutDelimiter,
-         @RequestParam(value = "byte", required = true) byte[] _byte,
+         @RequestParam(value = "byte", required = true) String _byte /* base64 encoded binary */,
          @RequestParam(value = "integer", required = false) Integer integer,
          @RequestParam(value = "int32", required = false) Integer int32,
          @RequestParam(value = "int64", required = false) Long int64,

samples/client/petstore/spring-http-interface-reactive-noResponseEntity/src/main/java/org/openapitools/api/FakeApi.java

@@ -220,7 +220,7 @@ Mono<Void> testEndpointParameters(
          @RequestPart(value = "number", required = true) BigDecimal number,
          @RequestPart(value = "double", required = true) Double _double,
          @RequestPart(value = "pattern_without_delimiter", required = true) String patternWithoutDelimiter,
-         @RequestPart(value = "byte", required = true) byte[] _byte,
+         @RequestPart(value = "byte", required = true) String _byte /* base64 encoded binary */,
          @RequestPart(value = "integer", required = false) Integer integer,
          @RequestPart(value = "int32", required = false) Integer int32,
          @RequestPart(value = "int64", required = false) Long int64,

samples/client/petstore/spring-http-interface-reactive/src/main/java/org/openapitools/api/FakeApi.java

@@ -211,7 +211,7 @@ Mono<ResponseEntity<Void>> testEndpointParameters(
          @RequestPart(value = "number", required = true) BigDecimal number,
          @RequestPart(value = "double", required = true) Double _double,
          @RequestPart(value = "pattern_without_delimiter", required = true) String patternWithoutDelimiter,
-         @RequestPart(value = "byte", required = true) byte[] _byte,
+         @RequestPart(value = "byte", required = true) String _byte /* base64 encoded binary */,
          @RequestPart(value = "integer", required = false) Integer integer,
          @RequestPart(value = "int32", required = false) Integer int32,
          @RequestPart(value = "int64", required = false) Long int64,