org.hibernate.TransientObjectException: The given object has a null identifier

hibernate的主键也需要自己管理。特别是当用update的时候，主键为自增，若不进行管理，不对其赋所修改的值时会报如下错误。

org.hibernate.TransientObjectException: The given object has a null identifier: com.demo.hibernate.beans.Address
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.getUpdateId(DefaultSaveOrUpdateEventListener.java:272)
at org.hibernate.event.def.DefaultUpdateEventListener.getUpdateId(DefaultUpdateEventListener.java:69)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsDetached(DefaultSaveOrUpdateEventListener.java:240)
at org.hibernate.event.def.DefaultUpdateEventListener.performSaveOrUpdate(DefaultUpdateEventListener.java:56)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
at org.hibernate.impl.SessionImpl.fireUpdate(SessionImpl.java:592)
at org.hibernate.impl.SessionImpl.update(SessionImpl.java:580)
at org.hibernate.impl.SessionImpl.update(SessionImpl.java:572)
at com.demo.hibernate.dao.AddressDAOImpl.update(AddressDAOImpl.java:122)
at com.demo.hibernate.service.AddressServiceImpl.update(AddressServiceImpl.java:33)
at com.demo.hibernate.test.AddressServiceTest.testUpdate(AddressServiceTest.java:71)
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:597)
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 junit.framework.TestSuite.runTest(TestSuite.java:208)
at junit.framework.TestSuite.run(TestSuite.java:203)
at org.eclipse.jdt.internal.junit.runner.junit3.JUnit3TestReference.run(JUnit3TestReference.java:130)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

在更新用户信息时只是对除了主键外的其他信息进行了显示，以为设了自增就不用管它了，谁知报错了，然后我又加上了主键属性，没有提示报错,加油。