How to determine JAX-RS resource paths programatically?

Question

Suppose I have a set of JAX-RS locators and sublocators, like the following:

@Path("/users")
public class UserListResource {
   @Path("/{id}")
   public UserResource getCustomer(@PathParam("id") int id) {
      // Find and return user object
   }
}

public class UserResource {
  @GET
  public String get() {...}
}

For example, a UserResource object with the ID 5 would have the path "/users/5". In my system, I have several different resources.

Now the question is: How can the server figure out the path of a given resource? Can I do this programmatically via some JAX-RS API or do I have to implement code that uses reflection? (I know how to do the latter, but would prefer the other approach.)

• At the point when I need to know the path, I do not have a request object at all. For example, I have a timer which does some background processing, then changes some entities in the domain model, then informs all clients about the changed entities (including their paths).
• I know that within the scope of a request, I can inject a UriInfo object that provides this, but I need to know the path in advance (to inform clients of a change that did not necessarily happen through the JAX-RS resource).
• I don't want to repeat the path information in another place, and I also don't want to have a set of path fragment constants for each resource type (in this case "/users" and "/{id}").

Answer 1

As I read your question, you need to build a URI knowing only the resource class and the id parameter.

It can be done using the UriBuilder class as in:

UriBuilder builder=UriBuilder.fromResource(UserListResource.class);
URI uri=builder.path(UserListResource.class,"getCustomer").build(5);

It uses reflection under the hood, so it is not so easy to refactor, but it is all it is available at the moment.