spring 初始化 在action中调用去出现java.lang.NullPointerException错误

Question

web.xml   <listener> <listener-class>org.springframework.web.util.Log4jConfigListener</listener-class> </listener> <!--监听器 用于初始化spring框架--> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> <!--上下文参数用于log4j以及spring中使用--><context-param> <param-name>webAppRootKey</param-name> <param-value>/WEB-INF/log4j.properties</param-value></context-param> <!--应用程序上下文参数,指定spring配置文件位置--><context-param> <param-name>contextConfigLocation</param-name> <param-value>classpath:bean.xml</param-value></context-param>     struts。xml <struts> <constant name="struts.devMode" value="true" /> <package name="default" namespace="/" extends="struts-default"> <action name="adduser" class="com.jsw.struts2.action.UserAction"> <result name="success"> /index.jsp </result> </action> </package> </struts>   UserAction.java public class UserAction extends ActionSupport { public String name; public String pass; public UserService userservice; public UserService getUserservice() { return userservice; } public void setUserservice(UserService userservice) { this.userservice = userservice; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getPass() { return pass; } public void setPass(String pass) { this.pass = pass; } public String execute() { this.adduser(); return "success"; } public void adduser() { userservice.adduser(); }   UserService.java   public class UserService { private UserDAO userdao; public UserDAO getUserdao() { return userdao; } public void setUserdao(UserDAO userdao) { this.userdao = userdao; } public void adduser() { System.out.println("111"); } }   bean.xml   <bean id="UserDAO" class="com.jsw.hibernate.dao.UserDAO"> <property name="sessionFactory" ref="sessionFactory"/> </bean> <bean id="UserService" class="com.jsw.hibernate.service.UserService"> <property name="userdao" ref="UserDAO"/> </bean> <bean id="LoginAction" class="com.jsw.struts2.action.LoginAction"> <property name="userservice" ref="UserService"/> </bean> <bean id="UserAction" class="com.jsw.struts2.action.UserAction"> <property name="userservice" ref="UserService"/> </bean>     结果在UserAction。java执行userservice.adduser();时出错。 Stacktraces java.lang.NullPointerException com.jsw.struts2.action.UserAction.adduser(UserAction.java:59) com.jsw.struts2.action.UserAction.execute(UserAction.java:45) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) java.lang.reflect.Method.invoke(Unknown Source) com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:452) com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:291) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:254) com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:263) org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:207) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:207) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:190) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:94) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:243) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:270) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:176) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:190) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:187) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52) org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:498) org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77) org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91) org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:859) org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:579) org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1555) java.lang.Thread.run(Unknown Source)

Answer 1

楼主struts.xml ,中实例化了action ，<action name="adduser" class="com.jsw.struts2.action.UserAction">  

而在spring 中也实例了action，这样实例化对象无法setter ,出现null ，

<bean id="UserAction" class="com.jsw.struts2.action.UserAction">
<property name="userservice" ref="UserService"/>
</bean>

楼主不妨修改为 

struts.xml 

<action name="adduser" class="这里就是spring 注册的action bean 的id">

eg:<action name="adduser" class="UserAction">

 

spring.xml 

<bean id="UserAction" class="com.jsw.struts2.action.UserAction" scope="prototype">
　　<property name="userservice" ref="UserService"/>
</bean>