如何使用Criteria API从Hibernate中的实体获取列表？

Question

Recently I've encountered problems using Criteria API. It is my very first contact with it. Here is part of my OfficeEntity.

@Entity
@Table(name = "office")
public class OfficeEntity {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column (name = "office_id")
private Long id;

@OneToMany(cascade = CascadeType.ALL)
@JoinColumn(name="office_id", referencedColumnName = "office_id")
private List<WorkerEntity> workers = new ArrayList<>();

GOAL - GET LIST OF WORKERS ENTITIES FROM SPECIFIC OFFICE ENTITY. By now I've figured out how to achieve the goal by this:

    @Override
public List<WorkerEntity> getWorkersByOffice(long officeId) {

    CriteriaBuilder cb = entityManager.getCriteriaBuilder();
    CriteriaQuery<OfficeEntity> query = cb.createQuery(OfficeEntity.class);

    Root<OfficeEntity> office = query.from(OfficeEntity.class);
    query.select(office).where(cb.equal(office.get("id"),officeId));

    TypedQuery<OfficeEntity> typedQuery = entityManager.createQuery(query);
    OfficeEntity foundOffice = typedQuery.getSingleResult();

    return foundOffice.getWorkers();

}

And it works fine but I think I rely too much on Java List interface methods instead of Criteria API. Can I get this list of WorkerEntity (field "workers" in OfficeEntity) just by creating proper query in Criteria? If then, can any advise or proper solution be delivered?

Best regards, Newbie to Hibernate & Criteria.

Answer 1

I am assuming there is two way binding between Office and Worked entities. If not create parent entity in Worked using @ManyToOne annotation. Then the below code should work

---

@Override
    public List<WorkerEntity> getWorkersByOffice(long officeId) {

        CriteriaBuilder cb = entityManager.getCriteriaBuilder();
        CriteriaQuery<WorkerEntity> query = cb.createQuery(WorkerEntity.class);

        Root<WorkerEntity> worker= query.from(WorkerEntity.class);
        OfficeEntity office  = new OfficeEntity();
        office.setId(officeId);
        query.select(worker).where(cb.equal(worker.get("office"),office));

        TypedQuery<OfficeEntity> typedQuery = entityManager.createQuery(query);
        List<WorkerEntity> workerList= typedQuery.getResultList();

        return workerList;

    }