How to retrieve only certain fields of an entity in JPQL or HQL? What is the equivalent of ResultSet in JPQL or HQL?

Question

In JPQL, I can retrieve entities by :

query = entityManager.createQuery(\"select c from Category c\");
List categories = query.getResultList(         


        

Answer 1

In HQL you can use list() function to get a list of Object[] array that contains result rows:

Query query = session.createQuery("select c.id,c.name from Category c");
List rows = query.list();

in returned array 1-st element will be id, second - name.

for (Object[] row: rows) {
    System.out.println(" ------------------- ");
    System.out.println("id: " + row[0]);
    System.out.println("name: " + row[1]);
}

If you want to use hibernate's Criteria API, you should use Projections.

With JPA it will work the same way:

List rows = entityManager.createQuery(queryString).getResultList();