Add support for multipart and @FormParam annotation

[jamfor999]

Expected Behavior

@FormParam should not be transposed to @QueryValue in a multipart endpoint.

As per https://jakarta.ee/specifications/restful-ws/3.1/jakarta-restful-ws-spec-3.1.html#consuming_multipart_formdata:

@Path("widgets4")
public class WidgetsResource4 {

    @POST
    @Consumes(MediaType.MULTIPART_FORM_DATA)
    public Response postWidget(@FormParam("part1Name") String part1,
                               @FormParam("part2Name") InputStream part2,
                               @FormParam("part3Name") EntityPart part3) {...}
}

@FormParam represents a part of a Multipart request, not a QueryValue. But, here, the code is translating it to @QueryValue - this is wrong and will break HTTP clients.

Actual Behaviour

The above snippet should work correctly, with the @FormParam values being interpreted as part of the multipart form, not as query parameters.

Steps To Reproduce

1. Write a JAX-RS controller which uses @FormParam to indicate multipart form data
2. Test, it will break

Environment Information

No response

Example Application

I cannot provide a sample application right now as this was noticed in an enterprise setting.

Version

4.4.0

[graemerocher]

Micronaut is not currently a JAX-RS implementation, the annotations are designed to aid in porting code from JAX-RS. We are currently working to see if greater compatibility can be achieved but currently @FormParam is not supported and this should be a compilation error.

[jamfor999]

Micronaut is not currently a JAX-RS implementation, the annotations are designed to aid in porting code from JAX-RS. We are currently working to see if greater compatibility can be achieved but currently @FormParam is not supported and this should be a compilation error.

That's unfortunate that isn't supported. I couldn't find docs which specify how Multipart endpoints should be handled using this library, is it the List<EntityPart> approach?
(Also, are there other libraries that work as JAX-RS implementations for Micronaut? This was the only one that I can find that even related to JAX-RS)

[graemerocher]

the list of supported annotations and interfaces is documented here https://micronaut-projects.github.io/micronaut-jaxrs/latest/guide/#supportedApi

Note that you can use any Micronaut specific annotation like @Part CompletedFileUpload file