java Criteria Builder 在 Select 语句中创建新对象
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Criteria Builder Create new Object In Select Statement
提问by user1827052
I was wondering if it's possible to create such query like :
我想知道是否可以创建这样的查询：
em.createQuery(
"SELECT NEW EmpMenu(p.name, p.department.name) "
+ "FROM Project p ").getResultList();
also is it possible to do it via Specification:
也可以通过规范来做到这一点：
public Predicate toPredicate(Root<T> root, CriteriaQuery<?> query,
CriteriaBuilder cb) {
return ???;
}
Thanks in advance!
提前致谢！
回答by Mikko Maunu
Yes, Criteria API does have have construct similar to JPQL constructor expressions. Result class is set via constructmethod in CriteriaBuilder.
是的，Criteria API 确实具有类似于 JPQL 构造函数表达式的构造。结果类通过CriteriaBuilder 中的构造方法设置。
Your JPQL query expressed as an criteria query is:
您表示为条件查询的 JPQL 查询是：
CriteriaBuilder cb...
CriteriaQuery<EmpMenu> q = cb.createQuery(EmpMenu.class);
Root<Project> c = q.from(Project.class);
q.select(cb.construct(EmpMenu.class,
c.get("name"), c.get("department").get("name")));
