java - 添加到具有 `cascade="的集合后，在 Hibernate 中保存对象时发生 TransientObjectException，删除孤儿"`

Question

我无法使用 Hibernate 保存一个新对象，该对象包含一个嵌套集合，该集合在 Hibernate 中映射为具有 cascade="all, delete-orphan" .更具体地说，如果我保存祖父对象，它将失败并包含下面的堆栈跟踪。

尤其令人沮丧的是，我们遇到过几次这个问题，但它并没有始终出现在我们坚持的所有集合中，只有其中一些，而且我们对 Hibernate 的了解不够深入，无法找出常见原因。非常感谢这里的任何见解。

一般来说，当我试图追踪错误发生的情况时，我似乎经常不得不调试 Hibernate 的源代码，这对于这样一个成熟的库来说似乎很奇怪。这也是一个非常缓慢的过程，因为 Hibernate 内部结构对于只是尝试使用它的人来说可能非常复杂。

堆栈跟踪下方包含我的对象类的缩写版本、 hibernate 映射文件和重现案例。

编辑:使用 cascade="all"避免了错误，但失去了我们宁愿拥有的功能。正在违反的删除孤儿级联所做的假设是什么？如果我从 Hibernate 的角度做一些无效/非法的事情，我希望它根本无法持久化，不仅在启用删除孤儿时失败。

带有堆栈跟踪的错误

com.foo.server.services.db.exception.InvalidObjectException: org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.foo.server.model.house.conditioning.Duct
    at com.foo.server.services.db.Transaction.commit(Transaction.java:33)
    at com.foo.server.services.db.service.PersistenceManager.commitTransactionIfOpen(PersistenceManager.java:83)
    at com.foo.server.services.db.service.DataService.save(DataService.java:230)
    at com.foo.server.services.db.service.DataService.save(DataService.java:188)
    at com.foo.server.model.house.TestHousePlan_JDO.testAddDistributionSystemSave(TestHousePlan_JDO.java:55)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
    at org.junit.rules.TestWatcher$1.evaluate(TestWatcher.java:55)
    at org.junit.rules.RunRules.evaluate(RunRules.java:20)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.foo.server.model.house.conditioning.Duct
    at org.hibernate.engine.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:242)
    at org.hibernate.collection.AbstractPersistentCollection.getOrphans(AbstractPersistentCollection.java:919)
    at org.hibernate.collection.PersistentList.getOrphans(PersistentList.java:70)
    at org.hibernate.engine.CollectionEntry.getOrphans(CollectionEntry.java:373)
    at org.hibernate.engine.Cascade.deleteOrphans(Cascade.java:364)
    at org.hibernate.engine.Cascade.cascadeCollectionElements(Cascade.java:348)
    at org.hibernate.engine.Cascade.cascadeCollection(Cascade.java:266)
    at org.hibernate.engine.Cascade.cascadeAssociation(Cascade.java:243)
    at org.hibernate.engine.Cascade.cascadeProperty(Cascade.java:193)
    at org.hibernate.engine.Cascade.cascade(Cascade.java:154)
    at org.hibernate.event.def.AbstractFlushingEventListener.cascadeOnFlush(AbstractFlushingEventListener.java:154)
    at org.hibernate.event.def.AbstractFlushingEventListener.prepareEntityFlushes(AbstractFlushingEventListener.java:145)
    at org.hibernate.event.def.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:88)
    at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:49)
    at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1028)
    at com.foo.server.services.db.Transaction.commit(Transaction.java:28)
    ... 31 more

房屋计划.java

public class HousePlan
{
    Long id;
    List<DistributionSystem> distributionSystems = Lists.newArrayList();
    // Other fields excluded

    public HousePlan()
    {
        distributionSystems.add(new DistributionSystem());
    }

    // getters + setters
}

房屋平面图.hbm.xml

<hibernate-mapping package="com.foo.server.model.house">
  <class name="HousePlan" table="house_plan">
    <id name="id" column="id">
      <generator class="native" />
    </id>

    <list name="distributionSystems" cascade="all,delete-orphan" lazy="false">
      <key column="housePlanId" not-null="false" />
      <list-index column="housePlanIndex" />
      <one-to-many class="com.foo.server.model.house.conditioning.DistributionSystem" />
    </list>

    <!-- Other mappings excluded -->

  </class>
</hibernate-mapping>

分发系统.java

public class DistributionSystem
{
    Long id;
    List<Duct> ducts = Lists.newArrayList();
    // Other fields excluded

    public DistributionSystem()
    {
        ducts.add(new Duct());
        ducts.add(new Duct());
    }

    // getters + setters excluded
}    

分发系统.hbm.xml

<hibernate-mapping package="com.foo.server.model.house.conditioning">
  <class name="DistributionSystem" table="distribution_system">
    <id name="id" column="id">
      <generator class="native" />
    </id>

    <!-- Note the usage of `cascade="all,delete-orphan"` which is the normal solution to this problem -->
    <list name="ducts" cascade="all,delete-orphan" lazy="false">
      <key column="distributionSystemId" not-null="false" />
      <list-index column="distributionSystemIndex" />
      <one-to-many class="com.foo.server.model.house.conditioning.Duct" />
    </list>

    <!-- Other mappings excluded -->

  </class>
</hibernate-mapping>     

风管.java

public class Duct
{
    Long id;
    // Other fields excluded

    // Constructor excluded

    // getters + setters excluded
}    

管道.hbm.xml

<hibernate-mapping package="com.foo.server.model.house.conditioning">
  <class name="Duct" table="duct">
    <id name="id" column="id">
      <generator class="native" />
    </id>

    <!-- Other mappings excluded -->

  </class>
</hibernate-mapping> 

再现案例

包括我们如何使用 hibernate 的缩写实现。

public class ReproCase
{
    public static Session session = getSessionFactory().openSession();

    public static void main(String... args)
    {
        HousePlan plan = new HousePlan();

        // This save succeeds
        plan = save(plan);

        plan.getDistributionSystems().add(new DistributionSystem());

        // This save fails
        plan = save(plan);  
    }

    public static <T> T save(T object)
    {
        Transaction transaction = new Transaction(session);
        transaction.begin();

        // In our full app our object inheritance hierarchy allows for the
        // call to getId() 

        // Objects with null ids are transient. Objects with non-null ids are
        // not transient, but might be detached from the persistence context so
        // here we ensure the object is attached.

        if (object.getId() != null)
        {
            object = (T)session.merge(object);
        }

        try
        {
            session.saveOrUpdate(object);
        }
        catch (Exception e)
        {
            session.merge(object);
        }


        // This is where the TransientObjectException occurs
        session.flush();

        transaction.commit();

        return object;
    }
}

Answer 1

您应该删除列表的实例化:

List<Duct> ducts = Lists.newArrayList();

这种关系由 Hibernate(通过代理)管理，它无法处理标准列表......

这显然意味着您不能在构造函数中添加值，您必须等到 Hibernate 知道父级后才能添加默认值:

DistributionSystem ds = save(new DistributionSystem());
ds.getDucts().add(new Duct());
ds.getDucts().add(new Duct());
ds.getDucts().add(new Duct());
ds = save(new DistributionSystem());