我有这个实体:
public Entity {
@JoinTable(name = "entity_equivalents",
joinColumns = {
@JoinColumn(name = "entity_new")},
inverseJoinColumns = {
@JoinColumn(name = "entity_old")})
@OneToMany
private Set<Entity> equivalents;
我一直试图创建一个CriteriaQuery,从实体中选择等效项,但我不知道如何创建CriteriaQuery
public Set<Entity> findEquivalents(Entity p1) {
EntityManager em = getEntityManager();
CriteriaBuilder cb = em.getCriteriaBuilder();
// HERE is the problem
CriteriaQuery<Set<Entity>> query = cb.createQuery(); // <----
Root<Entity> root = query.from(Entity.class);
Expression<Set<Entity>> exx= root.get(Entity_.equivalents);
query.select(exx);
query.where(cb.equal(root.get(Entity_.id), p1.getId()));
return em.createQuery(query).getSingleResult();
}
在使用FetchType.EAGER
之类的实例时,我不想设置属性enti.getEquivalents();
或让EM打开并获取负载
临时解决方法(直到有人引导我揭示CriteriaQuery的奥秘):
return new HashSet<>(getEntityManager()
.createQuery("SELECT o.equivalents from Entity o where o.id=" + id)
.getResultList());