Getting logged in user in a RESTful Service

Hello,

i am trying to get the current logged in user in my REST Service.

I have tried many different solutions but nothing works.

My resource class which returns always Guest:

public class ReportConfigResource extends HttpServlet  {

    @Context private HttpServletRequest req;

    @Context private HttpServletResponse res;

     public ReportConfigResource(){

      }

    @Path("/getUserName")

    @GET

    @Consumes(javax.ws.rs.core.MediaType.APPLICATION_JSON)

    @Produces(javax.ws.rs.core.MediaType.APPLICATION_JSON)

    public String getUserName(){

        IUser user = UMFactory.getAuthenticator().getLoggedInUser();

        return user.getDisplayName().toString();

    }

}

same code changed to:

IUser user = UMFactory.getAuthenticator().getLoggedInUser(req, res);

gives me a null object.

Any ideas?

Thanks.