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[JAVA-SPRING] Convert byte[] to String for operation params [QueryParam; PathParam; HeaderParam; CookieParam; FormParam] #22930

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[JAVA-SPRING] Convert byte[] to String for operation params [QueryParam; PathParam; HeaderParam; CookieParam; FormParam] #22930

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59bd0eb
convert byte[] to String for operation params
Picazsoo Feb 9, 2026
78499b6
add unit tests
Picazsoo Feb 9, 2026
02a530a
clean up open api spec
Picazsoo Feb 9, 2026
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1 change: 1 addition & 0 deletions ...enapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJavaCodegen.java
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Expand Up @@ -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");
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21 changes: 21 additions & 0 deletions ...les/openapi-generator/src/main/java/org/openapitools/codegen/languages/SpringCodegen.java
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Expand Up @@ -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);
Expand All @@ -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);

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2 changes: 1 addition & 1 deletion modules/openapi-generator/src/main/resources/JavaSpring/cookieParams.mustache
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@@ -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}}
2 changes: 1 addition & 1 deletion modules/openapi-generator/src/main/resources/JavaSpring/formParams.mustache
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@@ -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}}
2 changes: 1 addition & 1 deletion modules/openapi-generator/src/main/resources/JavaSpring/headerParams.mustache
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{{#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}}
2 changes: 1 addition & 1 deletion modules/openapi-generator/src/main/resources/JavaSpring/pathParams.mustache
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{{#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}}
2 changes: 1 addition & 1 deletion modules/openapi-generator/src/main/resources/JavaSpring/queryParams.mustache
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{{#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}}
14 changes: 14 additions & 0 deletions ...napi-generator/src/test/java/org/openapitools/codegen/java/assertions/PropertyAssert.java
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Expand Up @@ -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());
}
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86 changes: 86 additions & 0 deletions ...enapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java
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Expand Up @@ -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[]
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@cubic-dev-ai cubic-dev-ai bot Feb 9, 2026 •
edited
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P2: Form/multipart DTO still asserts format: byte as byte[], but Spring’s default data binding does not Base64‑decode form strings to byte[]; it converts the string to raw bytes. This makes form DTO binding inconsistent with the new String parameter handling and can yield incorrect values without a custom converter.

Prompt for AI agents 
Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java, line 944:

<comment>Form/multipart DTO still asserts `format: byte` as `byte[]`, but Spring’s default data binding does not Base64‑decode form strings to `byte[]`; it converts the string to raw bytes. This makes form DTO binding inconsistent with the new `String` parameter handling and can yield incorrect values without a custom converter.</comment>

<file context>
@@ -864,6 +864,92 @@ public void testSchemaImplements() throws IOException {
+        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
</file context>
Fix with Cubic


// 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();
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157 changes: 157 additions & 0 deletions modules/openapi-generator/src/test/resources/3_0/spring/byte-format-edge-cases.yaml
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@@ -0,0 +1,157 @@
openapi: 3.0.3
info:
title: Byte Format Edge Cases
version: 1.0.0

paths:
/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
2 changes: 1 addition & 1 deletion ...re/spring-http-interface-noResponseEntity/src/main/java/org/openapitools/api/FakeApi.java
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Expand Up @@ -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,
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2 changes: 1 addition & 1 deletion ...-http-interface-reactive-noResponseEntity/src/main/java/org/openapitools/api/FakeApi.java
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Expand Up @@ -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,
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2 changes: 1 addition & 1 deletion ...t/petstore/spring-http-interface-reactive/src/main/java/org/openapitools/api/FakeApi.java
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Expand Up @@ -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,
Expand Down
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