Is it possible to define a jax-rs service interface separated from its implementation (with eclipse and jersey)?

Question

I don\'t know if the title is confusing, but let\'s say I have this interface:

@Produces(MediaType.APPLICATION_JSON)
@Path(\"/user\")
public interface UserSe         


        

Answer 1

You can use annotation inheritance only if you don't use any jax-rs annotation on the implementing class: it is stated on section 3.6 of JSR-339.

You redefine @Path and @Produces for the method but not for the class.

So the Path annotation in your code should be on the concrete class:

public interface UserService {

    @GET
    @Path("/{userId}")
    @Produces(MediaType.APPLICATION_JSON)
    public Response getUser(@PathParam("userId") Long userId);

}


@Path("/user")
class UserServiceImpl implements UserService {

    @Override
    @GET
    @Path("/{userId}")
    @Produces(MediaType.APPLICATION_JSON)
    public Response getUser(@PathParam("userId") Long userId) {
        // TODO Auto-generated method stub
        return null;
    }

}

BTW, the specification encourages us to replicate the annotations on the concrete classes:

For consistency with other Java EE specifications, it is recommended to always repeat annotations instead of relying on annotation inheritance.

Answer 2

I had a similar issue working with interface automatically generated using the OpenAPI generator. The problem here was that I couldn't easily remove the @Path annotation from the interface and additionally adding it to the class caused ambiguity issues.

Problems with @Path-annotated interfaces however only occurs for resources that are automatically discovered on registered packages. For registered packages, all classes (and unfortunately interfaces as well) that are annotated with @Path will be instantiated.

To prevent that, you can just register your resources manually with your ResourceConfig as in the following example:

new ResourceConfig()
    .registerClasses(UserServiceImpl.class);

Just make sure, your interfaces are not in a package that are registered with your ResourceConfig. Using this approach, you can use the implementation from your example and also the @Path annotation added to the interface will be interpreted correctly.

Disclaimer: There probably should not be any @Path path annotation on the interface in the first place, but unfortunately this is what the OpenAPI generator creates. If you find yourself in a similar situation, I hope this helps. Otherwise, you should refer to the accepted answer.