How to paginate a JPA Query

Question

I have a submission table with columns like ID, Name, Code among other properties. My requirement is to search for records based on the me

Answer 1

For all JPA query objects (except for native SQL queries), you would use pagination through the setMaxResults(int) and setFirstResult(int) methods. For instance:

  return em.createNamedQuery("yourqueryname", YourEntity.class)
      .setMaxResults(noOfRecords)
      .setFirstResult(pageIndex * noOfRecords)
      .getResultList();

JPA will perform the pagination for you.

Named queries are just predefined and can be cached, while other types are dynamically created.
So the choice is to use JPQL like:

Query query = em.createQuery("SELECT s FROM Submission s WHERE s.code = :code or s.id = :id ORDER BY s.id", Submission.class);

Or CriteriaBuilder api to form a similar query:

    CriteriaBuilder qb = em.getCriteriaBuilder();
    CriteriaQuery cq = qb.createQuery(Submission.class);

    Root root = cq.from(Submission.class);
    cq.where( qb.or( 
        qb.equal(root.get("code"), qb.parameter(String.class, "code")),
        qb.equal(root.get("id"), qb.parameter(Integer.class, "id"))
    ));
    Query query = em.createQuery(cq);

Don't forget to set the parameter values using query.setParameter("id", sf.id) for example.