高手进,关于hibernate的

public void testAA2(){
HibernateUtil.beginTransaction();
Session session=HibernateUtil.getCurrentSession();
ClassRoom room=(ClassRoom)session.load(ClassRoom.class,new Integer(1));
Set set=room.getSet();
ClassRoom room1=new ClassRoom();
room1.setName("0002");
room1.setSet(set);
Iterator iter=set.iterator();
while(iter.hasNext()){
Student student=(Student)iter.next();
student.setRoomid(room1);
}
session.save(room1);
session.getTransaction().commit();
session.close();
}
这段程序出错了,怎么回事呀
org.hibernate.HibernateException: Found shared references to a collection: org.ldsj.pojo.ClassRoom.set
at org.hibernate.engine.Collections.processReachableCollection(Collections.java:163)
at org.hibernate.event.def.FlushVisitor.processCollection(FlushVisitor.java:37)
at org.hibernate.event.def.AbstractVisitor.processValue(AbstractVisitor.java:101)
at org.hibernate.event.def.AbstractVisitor.processValue(AbstractVisitor.java:61)
at org.hibernate.event.def.AbstractVisitor.processEntityPropertyValues(AbstractVisitor.java:55)
at org.hibernate.event.def.DefaultFlushEntityEventListener.onFlushEntity(DefaultFlushEntityEventListener.java:124)
at org.hibernate.event.def.AbstractFlushingEventListener.flushEntities(AbstractFlushingEventListener.java:195)
at org.hibernate.event.def.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:76)
at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:26)
at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:985)
at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:333)
at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:106)
at org.ldsj.test.Test2.testAA2(Test2.java:58)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at junit.framework.TestCase.runTest(TestCase.java:154)
at junit.framework.TestCase.runBare(TestCase.java:127)
at junit.framework.TestResult$1.protect(TestResult.java:106)
at junit.framework.TestResult.runProtected(TestResult.java:124)
at junit.framework.TestResult.run(TestResult.java:109)
at junit.framework.TestCase.run(TestCase.java:118)
at org.eclipse.jdt.internal.junit.runner.junit3.JUnit3TestReference.run(JUnit3TestReference.java:128)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)

org.hibernate.HibernateException: Found shared references to a collection: org.ldsj.pojo.ClassRoom.set
这个set集合成共享的引用了

Set set=room.getSet(); //这个set也是持久久对象，

下面代码中不能使用这个set，应该要克隆一份，再进行操作