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

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.