org.hibernate.TransientObjectException: entity.User

exception

javax.servlet.ServletException: org.springframework.dao.InvalidDataAccessApiUsageException: entity.User; nested exception is org.hibernate.TransientObjectException: entity.User
org.apache.struts.action.RequestProcessor.processException(RequestProcessor.java:523)
org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:421)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
web.tools.UTF8.doFilter(UTF8.java:16)

root cause

org.springframework.dao.InvalidDataAccessApiUsageException: entity.User; nested exception is org.hibernate.TransientObjectException: entity.User
org.springframework.orm.hibernate3.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:634)
org.springframework.orm.hibernate3.HibernateTransactionManager.convertHibernateAccessException(HibernateTransactionManager.java:714)
org.springframework.orm.hibernate3.HibernateTransactionManager.doCommit(HibernateTransactionManager.java:583)
org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:662)
org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:632)
org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:314)
org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:117)
org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:89)
org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
$Proxy4.addGoods(Unknown Source)
web.action.GoodsAction.doAdd(GoodsAction.java:107)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
org.apache.struts.actions.DispatchAction.dispatchMethod(DispatchAction.java:274)
org.apache.struts.actions.DispatchAction.execute(DispatchAction.java:194)
org.springframework.web.struts.DelegatingActionProxy.execute(DelegatingActionProxy.java:106)
org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:419)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
web.tools.UTF8.doFilter(UTF8.java:16)

root cause

org.hibernate.TransientObjectException: entity.User
org.hibernate.engine.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:216)
org.hibernate.type.EntityType.getIdentifier(EntityType.java:108)
org.hibernate.type.ManyToOneType.isDirty(ManyToOneType.java:221)
org.hibernate.type.TypeFactory.findDirty(TypeFactory.java:476)
org.hibernate.persister.entity.AbstractEntityPersister.findDirty(AbstractEntityPersister.java:2803)
org.hibernate.event.def.DefaultFlushEntityEventListener.dirtyCheck(DefaultFlushEntityEventListener.java:467)
org.hibernate.event.def.DefaultFlushEntityEventListener.isUpdateNecessary(DefaultFlushEntityEventListener.java:190)
org.hibernate.event.def.DefaultFlushEntityEventListener.onFlushEntity(DefaultFlushEntityEventListener.java:113)
org.hibernate.event.def.AbstractFlushingEventListener.flushEntities(AbstractFlushingEventListener.java:195)
org.hibernate.event.def.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:76)
org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:26)
org.hibernate.impl.SessionImpl.flush(SessionImpl.java:985)
org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:333)
org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:106)
org.springframework.orm.hibernate3.HibernateTransactionManager.doCommit(HibernateTransactionManager.java:575)
org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:662)
org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:632)
org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:314)
org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:117)
org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:89)
org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
$Proxy4.addGoods(Unknown Source)
web.action.GoodsAction.doAdd(GoodsAction.java:107)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
org.apache.struts.actions.DispatchAction.dispatchMethod(DispatchAction.java:274)
org.apache.struts.actions.DispatchAction.execute(DispatchAction.java:194)
org.springframework.web.struts.DelegatingActionProxy.execute(DelegatingActionProxy.java:106)
org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:419)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
web.tools.UTF8.doFilter(UTF8.java:16)

这个错误让我郁闷了好一段时间，现在终于搞懂了是什么缘故了！！！

update item之前 执行了item.setUserByBuyerId(new User()),此时的item是persistent状态，而userByBuyerId属性是一个transient状态的对象，并且cascade为默认的"none"(如果是all那么会试图创建一个新的User对象)，所以无法更新item。

<--都是 spring 的 formbackingObject 惹的麻烦，害我debuge了好长时间，希望大家不要再范类似错误了。-->

解决方案：从数据库中获取entity.User实例，而不能用new。

说明下，我的Good FormBean中有两个属性是用到User的Id这个外键的，所以在改造Good FormBean构造方法时，如果有一个属性允许为空，则不能用new创建这个实例(列：item.setUserBySalerId(new User())，若userBySalerId属性允许为空，就不用这样写了，直接去掉就好了)