Retrieving resource id in Restlet

what's the Restlet equivalent of the following snippet of code I'm using with Jersey:

  @GET
  @Path("{id}")
  @Produces({ MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON,MediaType.TEXT_XML})
  public Todo getEntityXMLOrJSON(@PathParam("id") int id)
  {
    ...
  }

I mean, when using Restlet framework I do the following:

public class ContactsApplication extends Application {
    public Restlet createInboundRoot() {
        Router router = new Router(getContext());
        router.attach("/contacts/{contactId}", ContactServerResource.class);
        return router;
    }
}

how do I retrieve contactId in the get method ?