在JPA2中，使用CriteriaQuery，如何计算结果

link之家

链接快照平台

输入网页链接，自动生成快照
标签化管理网页链接

相关文章推荐

低调的斑马 · eclipse断点调试 - CSDN文库· 1 年前 ·

瘦瘦的西瓜 · Jpa设置默认值约束_jpa给字段设置默认值 ...· 2 年前 ·

忐忑的烤地瓜 · 【20171110】- ...· 2 年前 ·

高大的电影票 · R-studio出现Error in ...· 3 年前 ·

腾讯云

开发者社区

文档意见反馈控制台

首页 TVP

文章/答案/技术大牛

发布

CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery<MyEntity> cq = cb
        .createQuery(MyEntityclass);
// initialize predicates here
return entityManager.createQuery(cq).getResultList().size();

CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Long> cq = cb.createQuery(Long.class);
cq.select(cb.count(cq.from(MyEntity.class)));
return em.createQuery(cq).getSingleResult();

CriteriaBuilder qb = entityManager.getCriteriaBuilder();
CriteriaQuery<Long> cq = qb.createQuery(Long.class);
cq.select(qb.count(cq.from(MyEntity.class)));
cq.where(/*your stuff*/);
return entityManager.createQuery(cq).getSingleResult();

public class Blah() {
    CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
    CriteriaQuery query = criteriaBuilder.createQuery();
    Root<Entity> root;
    Predicate whereClause;
    EntityManager entityManager;
    Class<Entity> domainClass;
    ... Methods to create where clause ...
    public Blah(EntityManager entityManager, Class<Entity> domainClass) {
        this.entityManager = entityManager;
        this.domainClass = domainClass;
        criteriaBuilder = entityManager.getCriteriaBuilder();
        query = criteriaBuilder.createQuery();
        whereClause = criteriaBuilder.equal(criteriaBuilder.literal(1), 1);
        root = query.from(domainClass);
    public CriteriaQuery<Entity> getQuery() {
        query.select(root);
        query.where(whereClause);
        return query;
    public CriteriaQuery<Long> getQueryForCount() {
        query.select(criteriaBuilder.count(root));
        query.where(whereClause);
        return query;
    public List<Entity> list() {
        TypedQuery<Entity> q = this.entityManager.createQuery(this.getQuery());
        return q.getResultList();
    public Long count() {
        TypedQuery<Long> q = this.entityManager.createQuery(this.getQueryForCount());
        return q.getSingleResult();
}

public static Long count(final EntityManager em, final CriteriaQuery<?> criteria)
    final CriteriaBuilder builder=em.getCriteriaBuilder();
    final CriteriaQuery<Long> countCriteria=builder.createQuery(Long.class);
    countCriteria.select(builder.count(criteria.getRoots().iterator().next()));
    final Predicate
            groupRestriction=criteria.getGroupRestriction(),
            fromRestriction=criteria.getRestriction();
    if(groupRestriction != null){
      countCriteria.having(groupRestriction);
    if(fromRestriction != null){
      countCriteria.where(fromRestriction);
    countCriteria.groupBy(criteria.getGroupList());
    countCriteria.distinct(criteria.isDistinct());
    return em.createQuery(countCriteria).getSingleResult();
  }

  public static <T> long count(EntityManager em,Root<T> root,CriteriaQuery<T> criteria)
    final CriteriaBuilder builder=em.getCriteriaBuilder();
    final CriteriaQuery<Long> countCriteria=builder.createQuery(Long.class);
    countCriteria.select(builder.count(root));
    for(Root<?> fromRoot : criteria.getRoots()){
      countCriteria.getRoots().add(fromRoot);
    final Predicate whereRestriction=criteria.getRestriction();
    if(whereRestriction!=null){
      countCriteria.where(whereRestriction);
    final Predicate groupRestriction=criteria.getGroupRestriction();
    if(groupRestriction!=null){
      countCriteria.having(groupRestriction);
    countCriteria.groupBy(criteria.getGroupList());
    countCriteria.distinct(criteria.isDistinct());
    return em.createQuery(countCriteria).getSingleResult();
  }

ProjectionList projection = Projections.projectionList();
projection.add(Projections.rowCount());
criteria.setProjection(projection);
Long totalRows = (Long) criteria.list().get(0);

    /*
     * (non-Javadoc)

在JPA2中，使用CriteriaQuery，如何计算结果

6 个回答