How to annotate JAX-RS on an interface while using Jersey

12
votes

This question had been asked a few times before, however the answers doesn't seem to work and/or Jersey has moved on with more changes.

I'm exposing some REST APIs using JAX-RS and Jersey (version 2.24). And I wish to annotate the interface with JAX-RS and a concrete implementation (without any annotations). However, since this patch Jersey stopped supporting this possibility. As far as I understand the spec, it doesn't strictly prohibit doing that.

If a subclass or implementation method has any JAX-RS annotations then all of the annotations on the superclass or interface method are ignored.

implying that it is totally okay to do that. In many cases it is good to use an interface, and have a server and client each have their respective implementations.

There are plenty of solutions out there,

  1. Use a ResourceConfig and do a registerClasses(MyImplementation.class) . However, this doesn't work.
  2. Disable the package scanning configuration in web.xml, create a custom javax.ws.rs.Application and do a register of your implementation from there. Doesn't work.
  3. use a ResourceConfig and define a custom AbstractBinder and do a bind so that Jersey's dependency injection can find the concrete implementations. Doesn't work.
  4. Use RESTEasy. RESTEasy doesn't seem to impose the interface restrictions as in Jersey. Never tried it myself.

I would appreciate if someone can share their experience with this. Any help on how to get Jersey working would be great too. As for the option (4) is it really necessary to switch ? A sample code below.

MyResource

 package com.foo;

import javax.ws.rs.GET;
import javax.ws.rs.Path;


@Path("/hello")
public interface MyResource {

  @GET
  public String sayHello();

}

MyResourceImpl

package com.bar;

public class MyResourceImpl implements MyResource {

  @Override
  public String sayHello() {
    return "Hello Jersey";
  }
}

Also have a web.xml that has the package scanning enabled to scan com.foo

2
javarestjerseyjax-rsjersey-2.0
Does it not work with the class level @Path on the concrete class instead of interface. This is how I've always known it to work (as described in the JAX-RS spec). I never even knew that interface class anno used to be supported. – Paul Samsotha
@dur yes, cxf or resteasy might support this. I believe jersey is a lot more easier to setup than cxf. – Alavalathi
@peeskillet it works with @Path annotation on the concrete class. But that defeats the purpose of using an interface in my case. The client and server has to use the same API path. And with your solution I'll end up duplicating the paths for client (my client is a javascript generated code from a swagger spec) – Alavalathi
May be duplicated stackoverflow.com/questions/35362956/… – tech2504
From the same paragraph of the JAX-RS spec that you quoted: JAX-RS annotations may be used on the methods and method parameters of a super-class or an implemented interface Note that it says methods only, so class-level annotations on interfaces are implied to be ignored. – Logan Pickup

2 Answers

1
votes

In Jersey,We should Put the class level @Path on the implementation instead of the interface.

package com.foo;

import javax.ws.rs.GET;
import javax.ws.rs.Path;


@Path("/hello")
public interface MyResource {

  @GET
  public String sayHello();

}


MyResourceImpl

package com.bar;
@Path("/hello")
public class MyResourceImpl implements MyResource {

  @Override
  public String sayHello() {
    return "Hello Jersey";
  }
}
0
votes

If you want to separate Resource interface from implementation (allowing you to use the interface with some REST client like resteasy client) you can use @RequestScoped on the implementation. Thus, this bean could use injected resources like EJB, EntityManager, ... Using your sample : 

import javax.ws.rs.GET;
import javax.ws.rs.Path;

@Path("/hello")
public interface MyResource {

   @GET
   public String sayHello();
}

MyResourceImpl

package com.bar;

@RequestScoped
public class MyResourceImpl implements MyResource {

  @Override
  public String sayHello() {
    return "Hello Jersey";
  }
}

Nevertheless, you have to take into consideration that as soon as you use specific JAX-RS classes in your implementation code (like UriInfo, Response object, ...) you will create a coupling between your implementation and the JAX-RS API.