Return total number of rows found while paging in JAX-RS resource

Question

I am creating a Jax-RS resource. I would like to return the total number of records in the response. I am using a named query and a header function to add a specific "Count" variable like following:

@GET
@Produces(MediaType.APPLICATION_JSON)
public Response findAll(
        @QueryParam("offset") int offset,
        @QueryParam("limit") int limit) {

    EntityManager em = factory.createEntityManager();
    Query query;
    try {

        query = em.createNamedQuery("User.getCount");
        String count = ((Long) query.getSingleResult()).toString();

        query = em.createNamedQuery("User.findAll");

        List<T> list = query.setFirstResult(safeOffset(offset))
                            .setMaxResults(safeLimit(limit))
                            .getResultList();

        return Response.ok(new GenericEntity<List<User>>(list) {})
                       .header("Count", count)
                       .build();

    } catch (Exception e) {
        return Response.serverError().build();
    } finally {
        em.close();
    }
}

I was wondering if there is a better way to calculate and return total number of records found?

Answer 1

You can have a look at this link ! It deals with ListResource to structure the JSON data returned : http://www.twilio.com/docs/api/rest/response#response-formats-list

http://twilio.github.io/twilio-java/com/twilio/sdk/resource/ListResource.html