必须管理实体以调用删除

Question

这里发生了什么？

@Stateless
@LocalBean
public class AppointmentCommentDao {
    public void delete(long appointmentCommentId) {
        AppointmentComment ac = em.find(AppointmentComment.class, appointmentCommentId);
        if (ac != null)
        {
            em.merge(ac);
            em.remove(ac);
        }
    }
    @PersistenceContext
    private EntityManager em;
}

在打电话给remove我得到一个IllegalArgumentException消息是Entity must be managed to call remove: ...., try merging the detached and try the remove again.

Answer 1

在您的情况下,不需要合并,因为在em.find和em.remove之间的任何点都不会释放ac .

通常,当实体被释放时,EntityManager的方法merge将实体作为参数并返回托管实例.作为参数给出的实体不会转换为附加.例如,这里解释了这一点:EntityManager.merge.你必须去:

    AppointmentComment toBeRemoved = em.merge(ac);
    em.remove(toBeRemoved);

Answer 2

试试这个:

entity = getEntityManager().getReference(AppointmentComment.class, entity.getId());
getEntityManager().remove(entity);