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

[Picazsoo]

This change updates the generator to correctly map OpenAPI format: byte fields across all locations.

• Query, Path, Header, Cookie, and Form fields: format: byte is generated as String (manual Base64 decoding required).
• Multipart text fields: String.
• Multipart file fields (format: binary): MultipartFile.
• JSON request body DTO fields: byte[], with automatic Base64 decoding via Jackson.
• Raw binary request bodies (application/octet-stream): Resource for streaming, no decoding applied.

This ensures all format: byte values are correctly typed across parameters and bodies, preserving the distinction between Base64-encoded values and raw binary.

The changes are practically limited to QueryParam; PathParam; HeaderParam; CookieParam; FormParam. But all the other types are asserted as well to prevent accidental regression.

fixes #22898

Tests performed:

Verified generated Java files for query, path, header, cookie, form, multipart, JSON body, and binary body fields.

Asserts confirm parameters and properties have the expected types (String, byte[], MultipartFile, Resource).

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---

Summary by cubic

Convert byte[] operation parameters to String in the Java Spring generator for query, path, header, cookie, and form params. Spring doesn’t auto-decode base64 for these, so we now accept the raw base64 string to prevent type issues.

• Bug Fixes

  • Map byte[] params in query/path/header/cookie/form to String in SpringCodegen; JavaSpring templates add “base64 encoded binary” comments.
  • Keep ByteArray → byte[] for models and JSON request bodies; raw binary bodies remain Resource; multipart binary fields use MultipartFile. Added explicit ByteArray → byte[] mapping in AbstractJavaCodegen.
  • Added tests with a focused OAS fixture (byte-format-edge-cases.yaml) covering params, DTO properties, multipart fields, JSON bodies, and binary bodies; minor spec cleanup.

• Migration

  • If you previously used byte[] for these params, decode the provided base64 String yourself (e.g., Base64.getDecoder().decode(value)).

^{Written for commit 02a530a. Summary will update on new commits.}

[cubic-dev-ai]

2 issues found across 41 files

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them.


<file name="samples/server/petstore/springboot-reactive-noResponseEntity/src/main/java/org/openapitools/api/FakeApi.java">

<violation number="1" location="samples/server/petstore/springboot-reactive-noResponseEntity/src/main/java/org/openapitools/api/FakeApi.java:383">
P2: @RequestPart is for multipart/form-data, but this endpoint consumes application/x-www-form-urlencoded. The modified parameter still uses @RequestPart, so WebFlux won’t bind the form body correctly (likely 400).</violation>
</file>

<file name="modules/openapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java">

<violation number="1" location="modules/openapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java:944">
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.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[cubic-dev-ai]

P2: @RequestPart is for multipart/form-data, but this endpoint consumes application/x-www-form-urlencoded. The modified parameter still uses @RequestPart, so WebFlux won’t bind the form body correctly (likely 400).

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At samples/server/petstore/springboot-reactive-noResponseEntity/src/main/java/org/openapitools/api/FakeApi.java, line 383:

<comment>@RequestPart is for multipart/form-data, but this endpoint consumes application/x-www-form-urlencoded. The modified parameter still uses @RequestPart, so WebFlux won’t bind the form body correctly (likely 400).</comment>

<file context>
@@ -380,7 +380,7 @@ default Mono<Void> testEndpointParameters(
         @ApiParam(value = "None", required = true) @DecimalMin(value = "67.8") @DecimalMax(value = "123.4") @Valid @RequestPart(value = "double", required = true) Double _double,
         @ApiParam(value = "None", required = true) @Pattern(regexp = "^[A-Z].*") @Valid @RequestPart(value = "pattern_without_delimiter", required = true) String patternWithoutDelimiter,
-        @ApiParam(value = "None", required = true) @Valid @RequestPart(value = "byte", required = true) byte[] _byte,
+        @ApiParam(value = "None", required = true) @Valid @RequestPart(value = "byte", required = true) String _byte /* base64 encoded binary */,
         @ApiParam(value = "None") @Min(value = 10) @Max(value = 100) @Valid @RequestPart(value = "integer", required = false) Integer integer,
         @ApiParam(value = "None") @Min(value = 20) @Max(value = 200) @Valid @RequestPart(value = "int32", required = false) Integer int32,
</file context>

[cubic-dev-ai]

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>