如何用JPA 2.0标准以M：N关系表示？

Question

How to express a query with JPA 2.0 Criteria that should fetch all entities A that are not in relation (m:n) with an Entity B.

Domain Model:

@Entity class A{
  @Id int id;
  @ManyToMany List<B> disableForB;
}

@Entity class B{
  @Id int id;
}

The problem related to this domain model is: How to find all A that are not in relation disableForB for an specific B ?

Answer 1

I do not have environment to test query available at the moment, so following can contain some mistake. This is anyway doable with isNotMember .

B b ...
CriteriaQuery<Aa> cq = cb.createQuery(A.class);
ParameterExpression<B> param = cb.parameter(B.class);
Root<A> a = cq.from(A.class);
Expression<Collection<B>> disabledB = a.get("disableForB");
Predicate pred = cb.isNotMember(param, disabledB);
cq.select(a);
cq.where(pred);
em.createQuery(cq).setParameter(param, b).getResultList();