Hibernate - 一对多关系和孤儿删除级联

Question

我有一个基本的一对多关系父/子关系，就像 Hibernate 参考书第 21 章中一样。
级联仅从子级到父级（保留级联只是因为我不想在删除子级时删除父级）。
当我向父级添加一个子级并保存子级时，我有一个 TransientObjectException...

@Entity
public class Parent implements Serializable {

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long id;

  @OneToMany(mappedBy = "parent", orphanRemoval = true)
  private List<Child> childs;

  public List<Child> getChilds() {
    return childs;
  }

  public void setChilds(List<Child> childs) {
    this.childs = childs;
  }

  public void addChild(Child child) {
    if (childs == null) childs = new ArrayList<Child>();
    if (childs.add(child)) child.setParent(this);
  }

  public Long getId() {
    return id;
  }

  public void setId(Long id) {
    this.id = id;
  }
}

@Entity
public class Child implements Serializable {

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long id;

  @ManyToOne(optional = false)
  @Cascade( { PERSIST, MERGE, REFRESH, SAVE_UPDATE, REPLICATE, LOCK, DETACH })
  private Parent parent;

  public Parent getParent() {
    return parent;
  }

  public void setParent(Parent parent) {
    this.parent = parent;
  }

  public Long getId() {
    return id;
  }

  public void setId(Long id) {
    this.id = id;
  }
}


@Test
public void test() {
  Parent parent = new Parent();
  Child child = new Child();
  parent.addChild(child);
  genericDao.saveOrUpdate(child);
}

但是在 saveOrUpdate 上，我有这个异常：

org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: Child
  at org.hibernate.engine.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:244)
  at org.hibernate.collection.AbstractPersistentCollection.getOrphans(AbstractPersistentCollection.java:911)
  at org.hibernate.collection.PersistentBag.getOrphans(PersistentBag.java:143)
  at org.hibernate.engine.CollectionEntry.getOrphans(CollectionEntry.java:373)
  at org.hibernate.engine.Cascade.deleteOrphans(Cascade.java:471)
  at org.hibernate.engine.Cascade.cascadeCollectionElements(Cascade.java:455)
  at org.hibernate.engine.Cascade.cascadeCollection(Cascade.java:362)
  at org.hibernate.engine.Cascade.cascadeAssociation(Cascade.java:338)
  at org.hibernate.engine.Cascade.cascadeProperty(Cascade.java:204)
  at org.hibernate.engine.Cascade.cascade(Cascade.java:161)
  at org.hibernate.event.def.AbstractSaveEventListener.cascadeAfterSave(AbstractSaveEventListener.java:476)
  at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:354)
  at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:204)
  at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:130)
  at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)
  at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)
  at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:117)
  at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
  at org.hibernate.impl.SessionImpl.fireSaveOrUpdate(SessionImpl.java:677)
  at org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:669)
  at org.hibernate.engine.CascadingAction$5.cascade(CascadingAction.java:252)
  at org.hibernate.engine.Cascade.cascadeToOne(Cascade.java:392)
  at org.hibernate.engine.Cascade.cascadeAssociation(Cascade.java:335)
  at org.hibernate.engine.Cascade.cascadeProperty(Cascade.java:204)
  at org.hibernate.engine.Cascade.cascade(Cascade.java:161)
  at org.hibernate.event.def.AbstractSaveEventListener.cascadeBeforeSave(AbstractSaveEventListener.java:451)
  at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:288)
  at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:204)
  at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:130)
  at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)
  at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)
  at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:117)
  at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
  at org.hibernate.impl.SessionImpl.fireSaveOrUpdate(SessionImpl.java:677)
  at org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:669)
  at org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:665)

我真的不明白，因为保存子级应该通过级联保存父级。 。 有什么想法吗？

更新1
这个问题似乎与“orphanRemoval”有关，因为如果我在父级上评论它：

@OneToMany(mappedBy = "parent" /*, orphanRemoval = true */)
private List<Child> childs;

它有效！
它拯救了孩子，然后是父母。
但当我从父级中删除子级时，我确实需要通过级联删除孤儿。

更新2
我创建了一个 JIRA 问题：
http://opensource.atlassian.com/projects/hibernate/browse/HHH-5364

更新3
似乎已修复:-)
http://opensource.atlassian.com/projects/hibernate/browse/HHH-2269

Answer 1

这是 Hibernate 中的一个问题，现已修复：

http://opensource.atlassian .com/projects/hibernate/browse/HHH-2269

Answer 2

基本上你违反了约束。数据库中与父级对应的行不存在，因此子级没有可以用来引用父级的外键关系。在为子级执行 do 之前，在父级上添加对 saveOrUpdate 的调用。

（编辑）我错过了您在重新格式化之前关于级联的评论。我的记忆是，级联不能以这种方式在上游工作。您仍然需要先保存父母。