JPA TypedQuery Arayüzü ve Sayfalama

Giriş

Sayfalama şu çağrılar ile yapılır

.setFirstResult(offset)

.setMaxResults (pageSize)

.getResultList ()

Örnek

Post nesnelerini çekmek için şöyle yaparız

public List<Post> filterPosts(Integer size, Integer offset) {
  CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
  CriteriaQuery<Post> criteriaQuery = criteriaBuilder.createQuery(Post.class);
  Root<Post> root = criteriaQuery.from(Post.class);

  // Optional: Add selection criteria/predicates
  // List<Predicate> predicates = new ArrayList<>();
  // predicates.add(criteriaBuilder.equal(root.get("status"), "published"));
  // CriteriaQuery<Post> query = criteriaQuery.where(predicates);

  List<Post> postList = entityManager
    .createQuery(criteriaQuery)
    .setFirstResult(offset)
    .setMaxResults(size)
    .getResultList();
  return postList;
}

Şöyle yaparız

int totalItemsCount(Predicate finalPredicate) {
  try {
    CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
    CriteriaQuery<Long> criteriaQuery = criteriaBuilder.createQuery(Long.class);
    
    Root<Post> root = criteriaQuery.from(Post.class);
    // Optional: If joins are involved, you need to specify
    // Join<Post, Comments> joinComments = root.join("comments");

    return Math.toIntExact(
      entityManager.createQuery(
        criteriaQuery.select(criteriaBuilder.count(root)).where(finalPredicate))
      .getSingleResult());
  } catch (Exception e) {
    log.error("Error fetching total count: {}", e.getMessage());
  }
  return 0;
}