错误There is no Action mapped for namespace / and action name—Struts2
Struts2出现错误，总是提示"There is no Action mapped for namespace / and action name"的错误。
错误代码如下：
09:36:13,515 WARN [Dispatcher] Could not find action or result There is no Action mapped for namespace [/] and action name [css] associated with context path [/ChinaUnicom]. - [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:39) at com.opensymphony.xwork2.DefaultActionProxyFactory.createActionProxy(DefaultActionProxyFactory.java:58) at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:534) at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77) at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Thread.java:619)
上网查询后发现这是一个初学者经常碰到的问题，导致错误的原因主要有两种。总结如下：
1.struts.xml文件错误。这种错误又分为以下几种：
1.1struts.xml文件名错误。一定要注意拼写问题；
1.2struts.xml文件放置路径错误。一定要将此文件放置在src目录下。编译成功后，要确认是否编译到classes目录中；
1.3struts.xml文件内容错误。下面给出一个正确的struts.xml文件以供参考。注意背景色部分。
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN" "http://struts.apache.org/dtds/struts-2.0.dtd"> <struts> <package name="default" namespace="/" extends="struts-default"> <action name="login" class="com.wanggc.struts2.sample.Struts2Action"> <result name="success">/jsp/result.jsp</result> </action> </package> </struts>
2.如果排除了struts.xml文件的问题，还有一种可能就是，在web.xml文件中的<welcome-file>信息中是否配置了自己工程的启动页面。如果没有配置，地址栏中要输入完成的url，如：http://localhost:8080/Struts2Sample/jsp/login.jsp，后面的资源详细信息不输入的时候也会报这个错误，我就是栽在这个问题上的(^_^)。