JPA Criteria API加入

Question

如何將此JPQL查詢轉換爲Criteria API？

select count(p) from Person p join p.glanceList g where p.duration < 1000 and g 
.duration < 1000 

Answer 1

試試這個。

CriteriaQuery<Long> q = cb.createQuery(Long.class); 
Root<Person> person = q.from(Person.class); 
Join<Person,Glance> glance = order.join("glanceList", JoinType.INNER); 
q.select(cb.count(person)) 
.where(cb.lt(person.get("duration"), 1000), cb.lt(glance.get("duration"), 1000)); 

假設Glance是類中加入的實體。

而且

CriteriaBuilder cb = em.getCriteriaBuilder();