struts2防止表单二次提交

<?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="avoidPackage" extends="struts-default">
        <action name="avoid" class="struts2.action.AvoidAction">
            <interceptor-ref name="token"></interceptor-ref>      //调用拦截器      
             <interceptor-ref name="defaultStack"></interceptor-ref>
             <result name="invalid.token">/error.jsp</result>      //二次提交时触发的result
            <result name="input">/input.jsp</result>
            <result name="success">/output.jsp</result>        
        </action>
    </package>

</struts>