CDI cannot retrieve servlet responde using @Context annotation

[opensas]

I have a jax-rs web service returning json, and I'd like to add cors headers to it.

so I Have the following class:

[...]
import javax.enterprise.context.RequestScoped;
import javax.servlet.http.HttpServletResponse;
import javax.ws.rs.Path;
[...]

@Stateful
@Path("/grupo")
@RequestScoped
@TransactionAttribute
public class GrupoEndpoint
{

   @Context
   private HttpServletResponse response;

    @GET
    public List<Grupo> listAll()
    {
        @SuppressWarnings("unchecked")
        final List<Grupo> results = em.createQuery("SELECT x FROM Grupo x").getResultList();
        // here response is null!!!
        response.addHeader("Access-Control-Allow-Origin", "*");
        response.addHeader("Access-Control-Allow-Methods", "GET, POST, OPTIONS");
        return results;
    }

But response is always null, is there something I might be missing?

Ps: I asked the same question on stackoverflow, in case you'd like to improve your SO reputation ;-)