今天在写一块程序的时候，出现了一个异常信息，捣鼓了一上午，终于找到了异常原因——不仅仅是简单的主键冲突问题

测试数据库：MySQL

异常信息如下：

org.hibernate.exception.ConstraintViolationException: could not insert: [org.xxx.entity.PropertyType]at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:94)at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:64)at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2176)at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2656)at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:71)at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:279)at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:321)at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:204)at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:130)at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56)at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50)at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:563)at org.hibernate.impl.SessionImpl.save(SessionImpl.java:551)at org.hibernate.impl.SessionImpl.save(SessionImpl.java:547)at org.xianfeng.hibernate.dao.HibernateDaoImpl.save(HibernateDaoImpl.java:110)at org.xianfeng.platform.property.service.impl.PropertyTypeServiceImpl.saveOrUpdate(PropertyTypeServiceImpl.java:58)at org.xianfeng.platform.test.TestPropTypeService.save(TestPropTypeService.java:31)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 org.junit.internal.runners.TestMethod.invoke(TestMethod.java:59)at org.junit.internal.runners.MethodRoadie.runTestMethod(MethodRoadie.java:98)at org.junit.internal.runners.MethodRoadie$2.run(MethodRoadie.java:79)at org.junit.internal.runners.MethodRoadie.runBeforesThenTestThenAfters(MethodRoadie.java:87)at org.junit.internal.runners.MethodRoadie.runTest(MethodRoadie.java:77)at org.junit.internal.runners.MethodRoadie.run(MethodRoadie.java:42)at org.junit.internal.runners.JUnit4ClassRunner.invokeTestMethod(JUnit4ClassRunner.java:88)at org.junit.internal.runners.JUnit4ClassRunner.runMethods(JUnit4ClassRunner.java:51)at org.junit.internal.runners.JUnit4ClassRunner$1.run(JUnit4ClassRunner.java:44)at org.junit.internal.runners.ClassRoadie.runUnprotected(ClassRoadie.java:27)at org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:37)at org.junit.internal.runners.JUnit4ClassRunner.run(JUnit4ClassRunner.java:42)at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:38)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)
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry '0' for key 1at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)at java.lang.reflect.Constructor.newInstance(Constructor.java:513)at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)at com.mysql.jdbc.Util.getInstance(Util.java:381)at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1015)at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3491)at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3423)at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1936)at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2060)at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2542)at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1734)at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2019)at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1937)at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1922)at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.executeUpdate(NewProxyPreparedStatement.java:105)at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:94)at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:57)... 40 more

通过异常信息可以确定——的确是数据库表的主键冲突了

但是定义主键的时候是指定为native自动生成的，可是为什么还会冲突呢？并且把hibernate的实体类映射文件修改为assigned还是会出现相同的异常，这就真是奇了怪了

在网上搜罗了一下，也有人遇到过Hibernate主键冲突的异常，通常的原因都是指定的主键相同或者没有把主键生成策略设置为native

可是我的程序明明都避免了这两个原因，为什么还是会出现了呢？

快中午的时候，无奈之下，全部删除重新写一遍的冲动都有，后来想了想还是先从头检查一遍吧。在检查的过程中，发现了主键冲突的真实原因——建表语句中的主键id没有自动增长，即没有指定为auto_increment

通过这次调试异常，似乎若有所思

1、Hibernate的异常机制还不是很完善，不能明确抛出具体的异常，以后在写框架的过程中也需要完善框架异常

2、解决问题要有一套好的方法，不到万不得已，不能删除重写，毕竟还是很耗费时间的

3、遇到问题要不烦不燥，虽然五一放假，但是也同样需要更多的耐心

。。。。。。