struts2中错误There is no Action mapped for namespace [/] and action name [] associated with context path

1 There is no Action mapped for namespace [/] and action name [] associated with context path [/Struts2_0300_Action2]. - [unknown location]
     at com.opensymphony.xwork2.DefaultActionProxy.prepare(DefaultActionProxy.java:185)
     at org.apache.struts2.impl.StrutsActionProxy.prepare(StrutsActionProxy.java:63)
     at org.apache.struts2.impl.StrutsActionProxyFactory.createActionProxy(StrutsActionProxyFactory.java:37)
     at com.opensymphony.xwork2.DefaultActionProxyFactory.createActionProxy(DefaultActionProxyFactory.java:58)
     at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:554)
     at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:81)
     at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:99)
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)
     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
     at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
     at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:442)
     at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1083)
     at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:640)
     at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
     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)

Struts问题确实让我很烦啊，调好了这个bug，出现下面这个bug，这个有事刚刚弄了一下午的问题。

查找了许多答案，

大致的解决方法如下

1：注意Struts.xml文件的位置，必须在src目录之下

2：

 <!DOCTYPE struts PUBLIC
     "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
     "http://struts.apache.org/dtds/struts-2.3.dtd">

这里面的Struts—2.3.dtd必须与自己的tomcat版本相一致。

3：

 <struts>
     <constant name="struts.devMode" value="true" />
     <package name="exercise"  extends="struts-default"  namespace="/" >

在struts文件中开发模式必须默认为true

最后发现虽然我的struts.xml文件位于src文件之下，但是

struts.xm位于src下是为了编译后能找到struts配置文件，必须确保其在WEB-INF之下

更改eclipse web 项目默认编译输出路径：

eclipse中只能针对项目更改，因为其默认的是build目录下的，只能以项目更改： 
项目右键 -》properties -》JavaBuild Path -》source -》Default output folder，选择你的路径，ok！

最后有个方法，如果找不到对应的可以直接在后面加上自己Action的名字