关于struts的There is no Action mapped for namespace [/] and action name....异常

最近调试struts程序时遇到如下异常：

Stacktraces

There is no Action mapped for namespace [/web] and action name [userAction!listAllUsers] associated with context path [/AndroidShop]. - [unknown location]

com.opensymphony.xwork2.DefaultActionProxy.prepare(DefaultActionProxy.java:185)
org.apache.struts2.impl.StrutsActionProxy.prepare(StrutsActionProxy.java:63)
org.apache.struts2.impl.StrutsActionProxyFactory.createActionProxy(StrutsActionProxyFactory.java:39)
com.opensymphony.xwork2.DefaultActionProxyFactory.createActionProxy(DefaultActionProxyFactory.java:58)
org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:553)
org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:99)
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:128)
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:293)
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
java.lang.Thread.run(Thread.java:619)

调用Acton的方式：http://localhost:8080/Test/web/userAction!listAllUsers.action.

错误原因：用“!“调用Action的方法时需开启Struts 2支持动态方法调用

解决办法：在struts.xml中加入：<constant name="struts.enable.DynamicMethodInvocation" value="true" />