Criteria Builder Create new Object In Select Statement

问题:

I was wondering if it's possible to create such query like :

em.createQuery(         "SELECT NEW EmpMenu(p.name, p.department.name) "             + "FROM Project p ").getResultList(); 

also is it possible to do it via Specification:

public Predicate toPredicate(Root<T> root, CriteriaQuery<?> query,         CriteriaBuilder cb) {       return ???; } 

Thanks in advance!

回答1:

Yes, Criteria API does have have construct similar to JPQL constructor expressions. Resuls class is set via construct method in CriteriaBuilder.

Your JPQL query expressed as an criteria query is:

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"))); 

文章来源: Criteria Builder Create new Object In Select Statement