struts配置默认Action

<package extends="struts-default" name="default" namespace="/">
    <default-action-ref name="NoAction"></default-action-ref>
    <action name="showWords" class="action.ShowWords">
        <result>/Hello.jsp</result>
        <result name="input">/index.jsp</result>
    </action>
    <action name="NoAction" >
        <result>/404.jsp</result>
    </action>
</package>

<action name="NoAction" >
    <result>/404.jsp</result>
</action>

package action;

public class NoAaction {

    public String execute(){
        return "success";
    }
}