java ssh 学习过程中的 遇到的异常解决记录

hibernate 联合主键出现的问题 

Exception in thread "main" org.hibernate.id.IdentifierGenerationException: null id generated for:class com.example.hibernate.model.Teacher

原因：

NULL 不能作为数据库Teacher表达的主键 猜测可能是由于在测试时没有插入主键数据

解决：

检查程序 发现程序果然没有插入联合主键的数据  插入联合主键数据后重新运行程序后正常。

tomcat  启动问题

validateJarFile(...\WEB-INF\lib\servlet-api.jar)-jar not loaded. See Servlet Spec 2.3, section 9.7.2. Offending class: javax/servlet/Servlet.class

解决方法：

1）删除项目WEB-INF/lib下的 servlet-api.jar

2）删除之前的发布文件夹

重新发布运行即可解决问题。

tomcat启动时要优先加载其lib下的包，这样就会出现冲突.

Unable to find parent packages json-default   

后来自己仔细看看tomcate启动日志发现了这个错误，经查询，是缺少了 

struts2-json-plugin-2.1.8.1.jar 这个包，因为struts2默认是以插件形式进行加载的，所以是少加载的json处理的包。加入这个包运行正常。

Caused by: Unable to load configuration. - action - file:/E:/apache-tomcat-6.0.36/webapps/SBStruts2/WEB-INF/classes/struts.xml

原因 如果struts.xml 位置正确的话 查看struts.xml 配置是否错误 发现如果action class类的具体路径不对的话 也会出现这种错误 很不容易发现

org.hibernate.exception.SQLGrammarException: could not insert: [com.example.po.Order]
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:92)
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:2327)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2834)
at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:71)
at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:273)
at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:320)
at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:203)
at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:129)
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:713)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:701)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:697)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:344)
at $Proxy5.save(Unknown Source)
at com.example.po.POTest.casecadeSaveCustomer(POTest.java:59)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:46)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
Caused by: com.mysql.jdbc.exceptions.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'order (ordername, customer_id) values ('o1', 3)' at line 1
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:936)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2934)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1616)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1708)
at com.mysql.jdbc.Connection.execSQL(Connection.java:3255)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1293)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1566)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1480)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1465)
at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:94)
at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:57)
... 46 more

检查代码无误后发现 有个持久化对象对应记录的表名为order 是mysql的关键字 所以会出现这种问题  改完表名就好了