使用JPA标准构建器进行复杂查询

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 

它的更好，如果我能找到它创建动态的基础上给出一个Map<String,String>使用元模型类或其他任何方式的参数的解决方案。

Answer 1

是这样的（不含元模型）：

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(); 

或用元模型（类型安全的，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();