三大框架@hibernate之JPA注解 | 开启单线程模式！

Hibernate 三大查询方式

1.ODI查询

2.HQL查询

public Order findBySn(String sn) {
        if (StringUtils.isEmpty(sn)) {
            return null;
        }
        String jpql = "select orders from Order orders where lower(orders.sn) = lower(:sn)";
        try {
            return entityManager.createQuery(jpql, Order.class).setParameter("sn", sn).getSingleResult();
        } catch (NoResultException e) {
            return null;
        }
    }

3.QBC查询

3.1 Criteria查询

3.2 CriteriaBuilder查询

3.2.1 单一条件count

public Long registerMemberCount(Date beginDate, Date endDate) {
        CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
        CriteriaQuery<Member> criteriaQuery = criteriaBuilder.createQuery(Member.class);
        Root<Member> root = criteriaQuery.from(Member.class);
        criteriaQuery.select(root);
        Predicate restrictions = criteriaBuilder.conjunction();
        if (beginDate != null) {
            restrictions = criteriaBuilder.and(restrictions, criteriaBuilder.greaterThanOrEqualTo(root.<Date>get("createDate"), beginDate));
        }
        if (endDate != null) {
            restrictions = criteriaBuilder.and(restrictions, criteriaBuilder.lessThanOrEqualTo(root.<Date>get("createDate"), endDate));
        }
        criteriaQuery.where(restrictions);
        return super.count(criteriaQuery, null);
    }

3.2.1 单一条件sum

public BigDecimal getChargePayCount(Long memberId){
       CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
       CriteriaQuery<BigDecimal> criteriaQuery = criteriaBuilder.createQuery(BigDecimal.class);
       Root<Order> root = criteriaQuery.from(Order.class);
       criteriaQuery.select(criteriaBuilder.sum(root.<BigDecimal> get("amount")));
       Predicate restrictions = criteriaBuilder.conjunction();

       if( memberId !=null){
           restrictions = criteriaBuilder.and(restrictions, criteriaBuilder.equal(root.<Long>get("member"),memberId));
       }
       criteriaQuery.where(restrictions);
       BigDecimal result = entityManager.createQuery(criteriaQuery).getSingleResult();
       return result != null ? result : BigDecimal.ZERO;
   }

3.2.1 多条件聚合

public Long getChargeElectricTimes(Long memberId){

        Boolean isDeleted = false;
        CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
        CriteriaQuery<Order> criteriaQuery = criteriaBuilder.createQuery(Order.class);
        Root<Order> root = criteriaQuery.from(Order.class);
        criteriaQuery.select(root);

        Predicate restrictions = criteriaBuilder.conjunction();
        if( memberId !=null){
            restrictions = criteriaBuilder.and(restrictions, criteriaBuilder.equal(root.<Long>get("member"),memberId),
                    criteriaBuilder.equal(root.<Boolean>get("isDeleted"),isDeleted));
        }
        criteriaQuery.where(restrictions);

        return super.count(criteriaQuery,null);
    }