Spring注入报空指针异常
java.lang.NullPointerException
    at com.szjz.system.serviceImpl.UserManagementAddServiceImpl.AddUser(UserManagementAddServiceImpl.java:24)
    at com.szjz.system.action.UserManagementAddAction.doExecute(UserManagementAddAction.java:84)
    at com.szjz.system.ute(BaseAction.java:22)
    at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
    at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
    at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
    at com.szjz.system.utils.MyActionServlet.doPost(MyActionServlet.java:38)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.ApplicationFilterChain.doFilter(nullpointerexception: nullApplicationFilterChain.java:206)
    at com.szjz.system.utils.EncodingFilter.doFilter(EncodingFilter.java:29)
    at org.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.StandardWrapperValve.invoke(StandardWrapperValve.java:
233)
    at org.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.StandardHostValve.invoke(StandardHostValve.java:128)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.tor.CoyoteAdapter.service(CoyoteAdapter.java:286)
    at http11.Http11AprProcessor.process(Http11AprProcessor.java:857)
    at http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:565)
    at at.util.AprEndpoint$Worker.run(AprEndpoint.java:1509)
    at java.lang.Thread.run(Thread.java:595)
解决方法：第一种：将你需要注入的参数设置为static的，然后将设值方法setXXX的返回值设置为非void型，比如你的
protected IDaoService daoService;  //注入类的属性
改为
protected static IDaoService daoService;  //注入类的属性