flush()未处理集合

Question

我正在尝试从双向关联中删除子元素。我要强调的是，如果我查询Employee实例，然后使用getChildren()方法获取关联的子代，那么父记录和子记录都将被管理。现在，当我调用child.setParent(null)和parent.getChildren().remove(child)时，这两个更新都应该在事务提交时持久化，但是我得到了：org.hibernate.AssertionFailure: collection [org.rand.model.Employee.children] was not processed by flush()异常，除非我对子元素调用merge或通过查询获取子元素。

有人能解释一下为什么会这样吗？

我使用的是hibernate 3.5.6-最终版

谢谢

更新:经过一段时间的调试，我找到了导致这个错误的代码，我一定是在发帖的时候不小心把它删除了。我对此表示诚挚的道歉。

罪魁祸首是自定义OneToManyInverseCheck bean验证器，该验证器正在验证父进程和子进程上是否都设置了关系。这在提交操作期间触发了附加实体(子项的子项)的加载。

实体：

@Entity
public class Employee {

    @Id
    @GeneratedValue(strategy=GenerationType.TABLE)
    private int id;

    @Version
    private int version;

    private String name;

    @ManyToOne
    private Employee parent;

    @OneToMany(mappedBy="parent")
    @OneToManyInverseCheck(inverseFieldName="parent")
    private List<Employee> children; 

    //get/set methods ommitted 
}

简单JUnit：

public class JPAUpdate {

    private static EntityManagerFactory emf;
    private EntityManager em;

    @BeforeClass
    public static void init() {
        emf = Persistence.createEntityManagerFactory("myapp-db");
    }

    @Before
    public void setUp() throws Exception {
        em = emf.createEntityManager();
    }

    @Test
    public void removeChildWithMerge() {
       em.getTransaction().begin();
       Employee e = em.createQuery("from Employee e where e.children is not empty order by e.id asc", Employee.class).getResultList().get(0);

        Employee child = e.getChildren().get(0);

        child.setParent(null);
        e.getChildren().remove(child);

        // removing this merge causes org.hibernate.AssertionFailure: collection [org.rand.model.Employee.children] was not processed by flush()
        em.merge(child);
        em.getTransaction().commit();
    }

    @Test
    public void removeChildWithFetch() {
        em.getTransaction().begin();
        Employee e = em.createQuery("from Employee e left join fetch e.children where e.children is not empty order by e.id asc", Employee.class).getResultList().get(0);

        Employee child = e.getChildren().get(0);
        child.setParent(null);
        e.getChildren().remove(child);
        //em.merge(child); - no merge needed
        em.getTransaction().commit();
    }

    @Test
    public void removeChild() {
        em.getTransaction().begin();
        Employee e = em.createQuery("from Employee e left join fetch e.children where e.children is not empty order by e.id asc", Employee.class).getResultList().get(0);

        Employee child = e.getChildren().get(0);
        child.setParent(null);
        e.getChildren().remove(child);
        //em.merge(child); - no merge needed
        em.getTransaction().commit();
    }
}

Answer 1

这可能是因为在removeChildWithMerge中，您的子集合是延迟加载的，并且在刷新期间触发了项的加载，从而导致了此异常。您可以使用Hibernate.inititalize(obj)而不是调用merge。另一方面，在removeChildWithFetch中，您正在使用fetch来急切地加载集合，因此在刷新期间集合items.So已经加载，所以没有问题。

Answer 2

对于我的案例，我用以下方式解决了它：

@PersistenceContext(type = PersistenceContextType.EXTENDED)
  private EntityManager entityManager;