第一次Hibernate之旅经验总结

1.错误提示：

Exception in thread "main" java.lang.NoClassDefFoundError: javax/persistence/EntityListeners
?at org.hibernate.cfg.annotations.reflection.JPAMetadataProvider.getDefaults(JPAMetadataProvider.java:96)
?at org.hibernate.annotations.common.reflection.java.JavaReflectionManager.getDefaults(JavaReflectionManager.java:226)
?at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1355)
?at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1826)
?at StudentTest.main(StudentTest.java:17)

原因：没有引入hibernate-distribution-3.6.0.Final\lib\jpa下面的hibernate-jpa-2.0-api-1.0.0.Final.jar

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2.错误提示：

Hibernate: insert into Student (name, age, id) values (?, ?, ?)
Exception in thread "main" org.hibernate.SessionException: Session was already closed
?at org.hibernate.impl.SessionImpl.close(SessionImpl.java:320)
?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:589)
?at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:344)
?at $Proxy0.close(Unknown Source)
?at StudentTest.main(StudentTest.java:22)

原因：在程序中有这么一句Session session = sf.getCurrentSession();将其改为Session session = sf.openSession();问题解决,或者用if(session.isOpen()）判断一下，具体原因不是很清楚，读者可以参考http://rmn190.javaeye.com/blog/370864

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3.错误提示：

Hibernate: insert into Student (name, age, id) values (?, ?, ?)
Exception in thread "main" org.hibernate.exception.ConstraintViolationException: Could not execute JDBC batch update
?at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:96)
?at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
?at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:275)
?at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:268)
?at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:184)
?at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:321)
?at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:51)
?at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1216)
?at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:383)
?at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:133)
?at StudentTest.main(StudentTest.java:21)
Caused by: java.sql.BatchUpdateException: Duplicate entry '7' for key 'PRIMARY'
?at com.mysql.jdbc.PreparedStatement.executeBatchSerially(PreparedStatement.java:1693)
?at com.mysql.jdbc.PreparedStatement.executeBatch(PreparedStatement.java:1108)
?at org.hibernate.jdbc.BatchingBatcher.doExecuteBatch(BatchingBatcher.java:70)
?at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:268)
?... 8 more

错误原因：主键的值不能重复，数据表中id=7的数据已经存在，所以导致插入数据失败！

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4.错误提示（使用Session session = sf.getCurrentSession()）：

Exception in thread "main" org.hibernate.HibernateException: No CurrentSessionContext configured!
?at org.hibernate.impl.SessionFactoryImpl.getCurrentSession(SessionFactoryImpl.java:683)
?at StudentTest.main(StudentTest.java:18)

错误原因：从3.0.1版本开始，Hibernate增加了 SessionFactory.getCurrentSession()方法。一开始，它假定了采用 JTA事务， JTA事务定义了当前session的范围和上下文(scope and context)。

错误主要原因是在hibernate.cfg.xml文件中忘记进行了如下设置：hibernate.current_session_context_class

如果是在web容器中运行hibernate，则在hibernate.cfg.xml中加入这句话：

<propertyname="hibernate.current_session_context_class">jta</property>

如果是在一个单独的需要进行JDBC连接的javaapplication中运行hibernate，则这样设置：

<propertyname="hibernate.current_session_context_class">thread</property>