I have 2 POJO classes in Java, Answer and Collaborator, in a many-to-many relationship.
class Answer {
@ManyToMany(cascade = CascadeType.ALL)
@JoinTable(name = "ANSWERS_COLLABORATORS", joinColumns = { @JoinColumn(name = "aid") }, inverseJoinColumns = { @JoinColumn(name = "cid") })
private Set<Collaborator> collaborators = new HashSet<Collaborator>(0);
}
Class Answer
has a set of Collaborator
, but a Collaborator
doesn't keep a set of Answer
. What I need to do from Hibernate CriteriaQuery
is to find the collaborators for an answer given by id.
I have already done this with Hibernate Criteria
( org.hibernate.Criteria
) using result transformer, but I'm stuck when it comes to using CriteriaQuery
, because I don't have a list of answers to give to the join.
It's done, finally...
Here's the code:
public List<Collaborator> getCollaborators(Long answerId) {
CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
CriteriaQuery<Collaborator> criteriaQuery = criteriaBuilder
.createQuery(Collaborator.class);
Root<Answer> answerRoot = criteriaQuery.from(Answer.class);
criteriaQuery.where(criteriaBuilder.equal(answerRoot.get(Answer_.id),
answerId));
SetJoin<Answer, Collaborator> answers = answerRoot
.join(Answer_.collaborators);
CriteriaQuery<Collaborator> cq = criteriaQuery.select(answers);
TypedQuery<Collaborator> query = entityManager.createQuery(cq);
return query.getResultList();
}
Using HQL:
You can use this:
Criteria criteria = session.createCriteria(Answer.class);
criteria.setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY);
criteria.createAlias("collaborators", "collaborators");
criteria.add(Restrictions.eq("collaborators.id",desiredCollaboratorId);
to get all the Answers associated to a certain Collaborator.
And this:
Criteria criteria = session.createCriteria(Answer.class);
criteria.setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY);
criteria.setFetchMode("collaborators", FetchMode.JOIN)
criteria.add(Restrictions.idEq(desiredAnswerId));
dsrTrackingCriteria.setProjection(Projections.property("collaborators"));
To get all Collaborators associated to a certain Answer.
Using JPA2 Criteria API you can do something like:
CriteriaBuilder cb = em.getCriteriaBuilder(); //creted from EntityManager instance
CriteriaQuery<Long> cq = cb.createQuery(Collaborator.class);
Root<Answer> rootAnswer = cq.from(Answer.class);
Join<Collaborator,Answer> joinAnswerCollaborator = rootAnswer.join("collaborators"); //(or rootAnswer.join(Answer_.collaborators); if you've created the metamodel with JPA2
Using criteria Builder :
Join<CLASS_A, CLASS_B> join = root.join(WHAT_UVE_DECLARED_IN_MAPPEDBY, JoinType.INNER);
searchCriteria.add(criteriaBuilder.like(join.get("FIELD_IN_SUBCLASS").as(String.class), "%blabla%"));
Join<Answer, Collaborator> join = root.join("collaborators ",JoinType.INNER); predicates.add(criteriaBuilder.equal(partnerEntityCityEntityJoin.get("id"),Long.parseLong(v)));
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