criteria-query-sample.java

@Repository
@Transactional
public class SingerServiceImpl implements SingerService {
    final static String ALL_SINGER_NATIVE_QUERY  =
        "select id, first_name,  last_name, birth_date,  version from singer";
    private Log log =
        LogFactory.getLog(SingerServiceImpl.class);
    @PersistenceContext
    private EntityManager  em;
    ...
    @Transactional(readOnly=true)
    @Override
    public List<Singer> findByCriteriaQuery(String firstName, String lastName) {
        log.info("Finding singer for firstName: " +  firstName
          + " and  lastName: " +  lastName);
        CriteriaBuilder cb  =  em.getCriteriaBuilder();
        CriteriaQuery<Singer> criteriaQuery = cb.createQuery(Singer.class);
        Root<Singer> singerRoot = criteriaQuery.from(Singer.class);
        singerRoot.fetch(Singer_.albums, JoinType.LEFT);
        singerRoot.fetch(Singer_.instruments, JoinType.LEFT);
        criteriaQuery.select(singerRoot).distinct(true);
        Predicate criteria = cb.conjunction();
        if (firstName != null) {
    Predicate p = cb.equal(singerRoot.get(Singer_.firstName),
        firstName);
     criteria =  cb.and(criteria, p);
        }
        if (lastName != null) {
    Predicate p = cb.equal(singerRoot.get(Singer_.lastName),
        lastName);
    criteria =  cb.and(criteria, p);
        }
        criteriaQuery.where(criteria);
        return em.createQuery(criteriaQuery).getResultList();
    }
}