Accessing either form or query parameters from a single annotated method parameter in Jersey

In Java Jersey (the JSR 311: JAX-RS reference implementation), you add Java Annotations to your POJOs to turn them in to RESTful resources. For example:

@Path("/posts")
public class PostsResource {
  @POST
  @Consumes(MediaType.APPLICATION_FORM_URLENCODED)
  public void post(@FormParam("title") String title, @FormParam("body") String body) {
    // Save new post 
  }
}

I came across this post on StackOverflow, asking for a way to combine form params and query params in a single resource @POST method. In other words, the poster wanted to know if he could do this:

@POST 
@Consumes(MediaType.APPLICATION_FORM_URLENCODED)
public void post(@BothParam("title") String title, @BothParam("body") String body) {
  // Save new post
}

The annotation @BothParam would allow you to create a post with either:

curl -d title=mytitle&body=mybody http://localhost:9998/posts

or:

curl -d body=mybody http://localhost:9999/posts?title=title

I'm also interested in a good solution to this question. I'm working on a project where I'd like to use Java Jersey, but need to support a legacy API which does not map elegantly into the RESTful paradigms that JAX-RS is designed to support.

One solution I'm exploring is an InjectableProvider which provides an Injectable for a custom annotation, such as BothParam.

The custom annotation, BothParam:

@Target({ ElementType.PARAMETER, ElementType.METHOD, ElementType.FIELD })
@Retention(RetentionPolicy.RUNTIME)
public @interface BothParam { 
  String value(); 
}

The injectable and injectable provider, BothParamInjectableProvider:

@Provider
public class BothParamInjectableProvider implements Injectable<String>, implements Injectable<BothParam, Type> {
  @Context HttpContext httpContext;

  private String parameterName;

  public BothParamInjectableProvider(@Context HttpContext httpContext) {
    this.httpContext = httpContext;
  }

  public String getValue() {
    if (httpContext.getRequest().getQueryParameters().containsKey(parameterName)) {
      return httpContext.getRequest().getQueryParameters().getFirst(parameterName);
    } else if (httpContext.getRequest().getFormParameters().containsKey(parameterName)) {
      return httpContext.getRequest().getFormParameters().getFirst(parameterName);
    }
    return null;
  }

  public ComponentScope getScope() {
    return ComponentScope.PerRequest;
  }

  public Injectable getInjectable(ComponentContext componentContext, BothParam bothParam, Type type) {
    this.parameterName = bothParam.getValue;
    return this;
  }
}