防止表单重复提交主要用的到标签是<s: token />，拦截器 <interceptor-ref name="token" />，还有一个默认的返回值<result name="invalid.token">/input.jsp</result>  




在页面加载时，<s: token />产生一个GUID（Globally Unique Identifier，全局唯一标识符）值的隐藏输入框如：
  1. <input type="hidden" name="struts.token.name" value="struts.token"/>   
  2. <input type="hidden" name="struts.token" value="BXPNNDG6BB11ZXHPI4E106CZ5K7VNMHR"/>  


同时，将GUID放到会话（session）中；在执行action之前，“token”拦截器将会话token与请求token比较，如果两者相同，则将会话中的token删除并往下执行，否则向actionErrors加入错误信息。如此一来，如果用户通过某种手段提交了两次相同的请求，两个token就会不同。

以下为action代码
import com.opensymphony.xwork2.ActionSupport;        
        
public class TestAction extends ActionSupport {                
        private static final long serialVersionUID = 6820659617470261780L;        
                
        private String message;        
                        
        public String getMessage() {        
                return message;        
        }        
        
        public void setMessage(String message) {        
                this.message = message;        
        }        
                
        @Override        
        public String execute() {        
                System.out.println("Executing action, your message is " + message);        
                return SUCCESS;        
        }                
}    

再看看JSP的写法
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8" %>        
<%@ taglib prefix="s" uri="/struts-tags" %>        
        
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">        
<html xmlns="http://www.w3.org/1999/xhtml">        
<head>        
        <title>struts2 test token</title>        
        <s:head />        
</head>        
<body>                
        <s:actionerror />        
        <s:form action="testAction" >        
                <s:textfield name="message" label="Message" />        
                <s:token />     <%-- 注意这里--%>        
                <s:submit />        
        </s:form>        
</body>        
</html>    

下面是struts2的配置文件
<?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="test" extends="struts-default" namespace="/testToken">        
                <action name="test" class="com.fhx.TestAction">        
                         <result name="invalid.token">/input.jsp</result>                                                        
                        <result>/input.jsp</result>        
        
                     <interceptor-ref name="defaultStack" />        
                     <interceptor-ref name="token" />        
        
                </action>        
        </package>        
</struts>    
 

以上XML片段值注意的是加入了“token”拦截器和“invalid.token”结果，因为“token”拦截器在会话token与请求token不一致时，将会直接返回“invalid.token”结果。