Question

有人可以建议我如何使用JPA Criteria构建器API构建以下查询吗？

SELECT id,status,created_at from transactions where status='1' 
   and currency='USD' and appId='123' order by id

如果我能找到一个基于使用元模型类或任何其他方式作为Map<String,String>给出的参数动态创建的解决方案，那就更好了。

Answer 1

就像这样（没有元模型）：

Map<String, Object> params = ...;
CriteriaBuilder cb = em.getCriteriaBuilder();           
CriteriaQuery<Tuple> cq = cb.createTupleQuery();     
Root<Transaction> r = cq.from(Transaction.class);

Predicate p= cb.conjunction();
for (Map.Entry<String, Object> param: params.entrySet())
    p = cb.and(p, cb.equal(r.get(param.getKey()), param.getValue()));

cq.multiselect(r.get("id"), r.get("status"), r.get("created_at"))
    .where(p)
    .orderBy(cb.asc(r.get("id")));

List<Tuple> result = em.createQuery(cq).getResultList();

或使用元模型（类型安全，但有点罗嗦）：

Map<SingularAttribute<Transaction, ?>, Object> params = ...;
CriteriaBuilder cb = em.getCriteriaBuilder();           
CriteriaQuery<Tuple> cq = cb.createTupleQuery();     
Root<Transaction> r = cq.from(Transaction.class);

Predicate p= cb.conjunction();
for (Map.Entry<SingularAttribute<Transaction, ?>, Object> param: params.entrySet())
    p = cb.and(p, cb.equal(r.get(param.getKey()), param.getValue()));

cq.multiselect(r.get(Transaction_.id), r.get(Transaction_.status), 
          r.get(Transaction_.created_at))
    .where(p)
    .orderBy(cb.asc(r.get(Transaction_.id)));

List<Tuple> result = em.createQuery(cq).getResultList();

使用JPA Criteria构建器的复杂查询

1 个答案: