spring注入bean不成功，求普及知识

Question

先粘上错误信息：2013-06-08 01:21:28 ERROR [http-8080-3] (ExceptionMappingInterceptor.java:229) - 
java.lang.NullPointerException
at com.app.pw.guangdong.electrify.action.ElectrifyAction.getTaskList(ElectrifyAction.java:110)
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 com.opensymphony.xwork.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:364)
at com.opensymphony.xwork.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:216)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:190)
at com.opensymphony.xwork.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:165)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.opensymphony.xwork.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:168)
at com.opensymphony.xwork.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.opensymphony.xwork.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:115)
at com.opensymphony.xwork.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:31)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:31)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:31)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.opensymphony.webwork.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:174)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:31)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.opensymphony.webwork.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:169)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:31)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.opensymphony.xwork.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:151)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:31)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:31)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:31)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.opensymphony.xwork.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:165)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.rich.framework.auth.interceptor.AuthenticationInterceptor.intercept(AuthenticationInterceptor.java:101)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.emmis.interceptor.GisLoginInterceptor.intercept(GisLoginInterceptor.java:65)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.opensymphony.webwork.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:174)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:188)
at com.opensymphony.xwork.DefaultActionProxy.execute(DefaultActionProxy.java:113)
at com.opensymphony.webwork.dispatcher.DispatcherUtils.serviceAction(DispatcherUtils.java:225)
at com.opensymphony.webwork.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:202)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at com.opensymphony.webwork.dispatcher.ActionContextCleanUp.doFilter(ActionContextCleanUp.java:88)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at com.rich.component.filter.MultiTabReturnBackFilter.doFilter(MultiTabReturnBackFilter.java:88)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at com.rich.framework.util.EncodingFilter.doFilter(EncodingFilter.java:39)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at com.rich.framework.util.CustomFilter.doFilter(CustomFilter.java:53)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:172)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:843)
at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:679)
at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1303)
at java.lang.Thread.run(Thread.java:619)
先说下自己测试之后的结果，我如果不调用at com.app.pw.guangdong.electrify.action.ElectrifyAction.getTaskList这个方法就不会出错，页面能正常跳转。 debug调试之后得到的答案是注入业务层失败，数据显示为空····求大神指点Spring

Answer 1

先声明，本人不是高手，也是菜鸟一枚，错误提示中“java.lang.NullPointerException”，说明找不到相应的类，你自己检查看看，是否加载了相应的类~

Answer 2

起码ElectrifyAction贴出来啊，不是找不到类，是空指针。

Answer 3

at com.app.pw.guangdong.electrify.action.ElectrifyAction.getTaskList你调用这个方法的时候传入的对象会不会有问题呢，报的是空指针啊，taskList属性有没有得到值？debug设个断点看看

Answer 4

spring 配置文件里面没有注入bean 吧

Answer 5

如果确定是注入问题，启动就有错的，那个日志才是关键。
LZ确认Spring配置文件是否有相应的bean配置，然后确认下启动日志是否有错吧~

Answer 6

 找不到类应该是classnotfound这个异常吧

Answer 7

把你的spring的配置文件贴上来看看啦
还有你说的那个业务层代码  贴全点才好分析啊

Answer 8

我告诉你，“getTaskList”方法不要用get或者set什么的开头，重新起个名字，因为spring的依赖注入跟set、get有关。

Answer 9

不给配置文件怎么看啊。SSH 中  空指针  基本都是注入失败对象为空，所以空指针调用了。。

Answer 10

谢谢楼上几位大侠的指教，是我理解错了。其实我对Spring的IOC机制也有些迷糊~

Answer 11

在你注入bean的时候，里面的值为空了

Answer 12

楼主，问题解决了么，我最近也出了一个这样的问题，是不是你的Spring里没有配置Action bean呢，

Answer 13

空指针异常，是你的页面数据传输到action 的时候 没传过来值

Answer 14

at com.app.pw.guangdong.electrify.action.ElectrifyAction.getTaskList(ElectrifyAction.java:110)
ElectrifyAction这个类第110行对空的对象进行了操作，报空指针异常

Answer 15

 用get或set开头的话 如果你前台用jquery 访问其他方法 它不回调回去 而且去执行set /get 开头的方法 。这样很容易爆空指针的

Answer 16

ElectrifyAction  这个类spring 没有生成实例吧