java.lang.IllegalArgumentException: attempt to create saveOrUpdate event with null entity

今天想把ssh整合的代码跑起来，控制台就一直在报错，搞了一天！！！

2016-06-05 16:39:12,196 ERROR [http-apr-80-exec-13] interceptor.ParametersInterceptor (ParametersInterceptor.java:229) - Developer Notification (set struts.devMode to false to disable this message):
Unexpected Exception caught setting 'name' on'class com.xxx.action.UserAction: Error setting expression 'name' with value ['xxxxxxx', ]

2016-06-05  16:39:12,225  [com.mashen.dao.UserDao]-[ERROR]
java.lang.IllegalArgumentException: attempt to create saveOrUpdate event with null entity
at org.hibernate.event.spi.SaveOrUpdateEvent.<init>(SaveOrUpdateEvent.java:62)
at org.hibernate.event.spi.SaveOrUpdateEvent.<init>(SaveOrUpdateEvent.java:45)
at org.hibernate.internal.SessionImpl.save(SessionImpl.java:707)
at org.hibernate.internal.SessionImpl.save(SessionImpl.java:702)
at com.mashen.dao.UserDao.addUser(UserDao.java:21)
at com.mashen.service.UserService.addUser(UserService.java:14)
at com.mashen.action.UserAction.add2(UserAction.java:40)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at ognl.OgnlRuntime.invokeMethod(OgnlRuntime.java:892)
at ognl.OgnlRuntime.callAppropriateMethod(OgnlRuntime.java:1522)
at ognl.ObjectMethodAccessor.callMethod(ObjectMethodAccessor.java:68)
at com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethodWithDebugInfo(XWorkMethodAccessor.java:96)
at com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethod(XWorkMethodAccessor.java:88)
at ognl.OgnlRuntime.callMethod(OgnlRuntime.java:1598)
at ognl.ASTMethod.getValueBody(ASTMethod.java:91)
at ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
at ognl.SimpleNode.getValue(SimpleNode.java:258)
at ognl.Ognl.getValue(Ognl.java:494)
at ognl.Ognl.getValue(Ognl.java:458)
at com.opensymphony.xwork2.ognl.OgnlUtil$2.execute(OgnlUtil.java:314)
at com.opensymphony.xwork2.ognl.OgnlUtil.compileAndExecute(OgnlUtil.java:345)
at com.opensymphony.xwork2.ognl.OgnlUtil.getValue(OgnlUtil.java:312)
at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:422)
at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:284)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)
at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:252)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:97)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:260)
at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:69)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:97)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:133)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:133)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:97)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:133)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:97)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:188)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:73)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at org.apache.struts2.interceptor.DateTextFieldInterceptor.intercept(DateTextFieldInterceptor.java:120)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:91)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:244)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:99)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:139)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:155)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:174)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:97)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:130)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:193)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:193)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at org.apache.struts2.factory.StrutsActionProxy.execute(StrutsActionProxy.java:54)
at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:556)
at org.apache.struts2.dispatcher.ExecuteOperations.executeAction(ExecuteOperations.java:81)
at org.apache.struts2.dispatcher.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:113)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:85)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:522)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1095)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:672)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2500)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2489)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)

at java.lang.Thread.run(Thread.java:745)

这个问题出错的原因是你url的请求参数跟你Action里声明的对象的名字对不上。例如我在UserAction.java文件里声明了一个对象
private User user;

public User getUser() {
return user;
}

public void setUser(User user) {
this.user = user;
}

并且User类里面有id和name两个属性。

还有我的form表单是这样写的:

<form action="add2.action">
姓名:<input type="text" name="name" value=""/><br/>
i  d:<input type="text" name="id" value=""/>
<input type="submit" value="提交"/>
</form>

问题就是出现在这里。

<form action="add2.action">
姓名:<input type="text" name="user.name" value=""/><br/>
i  d:<input type="text" name="user.id" value=""/>
<input type="submit" value="提交"/>
</form>

在name的值加上你在action定义的对象的名字(xxx.) ，就不会报错了！

希望能为解决你的问题提供参考，谢谢！