JPA count NamedQuery

Question

how to get count with a namedquery, without getting all the list (it would increase performance I think). This is the named query that doesn't work:

@NamedQuery(name = "Charakteristika.findAllCount", query = "SELECT COUNT(c) FROM Charakteristika c") 

Executing this:

System.out.println("a"); System.out.println(em.createNamedQuery("Charakteristika.findAllCount", Integer.class).getSingleResult().intValue()); System.out.println("b"); 

Output:

a 

Although this query works:

@NamedQuery(name = "Charakteristika.findAll", query = "SELECT c FROM Charakteristika c") 

Executing this:

System.out.println("a"); System.out.println(em.createNamedQuery("Charakteristika.findAll", Charakteristika.class).getResultList().size()); System.out.println("b"); 

Output:

a 11111 b 

Answer 1

Change your code likes this;

      int count = ((Number)em.createNamedQuery("Charakteristika.findAllCount").getSingleResult()).intValue();       System.out.println(count); 

Answer 2

Also you can try it: use TypeQuery interface with Long value. In the next example, "PosicionHistorialDia.findNumberSpeeding" query is a jpa count.

    @Override     public Long findCount(String eventCode) {          TypedQuery<Long> query = em.createNamedQuery(             "PosicionHistorialDia.findNumberSpeeding",             Long.class);         query.setParameter("event", eventCode);         return query.getSingleResult();     }