struts2-用token拦截器屏蔽重复提交问题
在服务器端生成一个随机值，然后传给客户端的form中，当客户端提交时，用隐含域提交给服务器端，提交后，
服务器端又把那个随机值清掉了，当你再次提交时，服务器端的那个随机值已经清掉了，所以提交失败

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE struts PUBLIC    "-//Apache Software Foundation//DTD Struts Configuration 2.1//EN"    "http://struts.apache.org/dtds/struts-2.1.dtd"><struts><constant name="struts.devMode" value="true"></constant><package name="test" namespace="/" extends="struts-default"><action name="input" name="code">package com.hugui.action;import com.opensymphony.xwork2.ActionSupport;public class InputAction extends ActionSupport {@Overridepublic String execute() throws Exception {return super.execute();}}

package com.hugui.action;import com.opensymphony.xwork2.ActionSupport;public class UserAction extends ActionSupport {private String name;private int age;@Overridepublic String execute() throws Exception {System.out.println("a user added!");return super.execute();}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}}