java.lang.reflect.InvocationTargetException
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at com.bjsxt.servlet.BaseServlet.service(BaseServlet.java:22)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at com.bjsxt.filter.MyBatisFilter.doFilter(MyBatisFilter.java:29)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at com.bjsxt.filter.LoginFilter.doFilter(LoginFilter.java:39)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.logging.log4j.core.web.Log4jServletFilter.doFilter(Log4jServletFilter.java:66)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:110)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:494)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:1025)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:445)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1136)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:318)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.base/java.lang.Thread.run(Thread.java:844)
Caused by: org.apache.ibatis.exceptions.PersistenceException:
### Error updating database. Cause: java.lang.NullPointerException
### The error may involve com.bjsxt.mapper.UserMapper.insUser-Inline
### The error occurred while setting parameters
### SQL: insert into t_user values (default, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
### Cause: java.lang.NullPointerException
at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:26)
at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:154)
at org.apache.ibatis.session.defaults.DefaultSqlSession.insert(DefaultSqlSession.java:141)
at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:51)
at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:52)
at com.sun.proxy.$Proxy15.insUser(Unknown Source)
at com.bjsxt.service.impl.UserServiceImpl.insUser(UserServiceImpl.java:35)
at com.bjsxt.servlet.AdminServlet.insUser(AdminServlet.java:22)
... 35 more
Caused by: java.lang.NullPointerException
at com.bjsxt.pojo.User.getCid(User.java:117)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at org.apache.ibatis.reflection.invoker.MethodInvoker.invoke(MethodInvoker.java:40)
at org.apache.ibatis.reflection.wrapper.BeanWrapper.getBeanProperty(BeanWrapper.java:154)
at org.apache.ibatis.reflection.wrapper.BeanWrapper.get(BeanWrapper.java:48)
at org.apache.ibatis.reflection.MetaObject.getValue(MetaObject.java:116)
at org.apache.ibatis.scripting.defaults.DefaultParameterHandler.setParameters(DefaultParameterHandler.java:76)
at org.apache.ibatis.executor.statement.PreparedStatementHandler.parameterize(PreparedStatementHandler.java:80)
at org.apache.ibatis.executor.statement.RoutingStatementHandler.parameterize(RoutingStatementHandler.java:61)
at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:74)
at org.apache.ibatis.executor.SimpleExecutor.doUpdate(SimpleExecutor.java:47)
at org.apache.ibatis.executor.BaseExecutor.update(BaseExecutor.java:105)
at org.apache.ibatis.executor.CachingExecutor.update(CachingExecutor.java:71)
at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:152)
... 41 more
在pojo实体类中将User类中的id，rid，cid从int类型改为了Integer，这是因为int类型不支持null，改为Integer更加方便安全。但是，将类型改为Integer后，我并没有修改get和set方法，其中的参数类型仍未int类型。这也就是错误产生的原因，进一步分析可知：
当我把id，rid，cid定义为Integer时，如果没有默认值，则为null，那么当下面用到get和set但get和set却是int类型的，这是就会自动发生拆箱操作，但是并不存在这个值让你去拆箱；所以会报错；