出现表单重复提交的三种情况：
一、服务器响应缓慢，用户多次点击提交按钮。
二、提交成功后刷新页面。
三、提交成功后返回表单页面再次点击提交。
package com.jalja.token; import java.io.IOException; import java.io.PrintWriter; import java.util.UUID; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class UserServlet extends HttpServlet{ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request, response); } public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { request.setCharacterEncoding("utf-8"); response.setContentType("text/html;charset=utf-8"); String contextPath=request.getContextPath(); String requestURI=request.getRequestURI(); String path=requestURI.substring(contextPath.length()+1, requestURI.length()); String token=""; if(path.equals("index.do")){ token = UUID.randomUUID().toString();//创建令牌 System.out.println("在FormServlet中生成的token："+token); request.getSession().setAttribute("token", token); //在服务器使用session保存token(令牌) request.getRequestDispatcher("/index.jsp").forward(request, response);//跳转到form.jsp页面 } if(path.equals("token.do")){ String name=request.getParameter("username"); String tokenValue=request.getParameter("tokenValue");//获取客户端的Token System.out.println("获取客户端的token："+tokenValue); String server_token = (String) request.getSession().getAttribute("token");//获取服务器端的token if(tokenValue!=null && server_token!=null && server_token.equals(tokenValue)){ System.out.println("处理请求; 获得name==》"+name); try { Thread.sleep(3*1000);//模拟网络延迟 } catch (InterruptedException e) { e.printStackTrace(); } }else{ System.out.println("不处理"); } request.getSession().removeAttribute("token");//每次处理玩请求都要移除掉token } } }
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML>
<html>
<head>
<title>Form表单</title>
</head>
<body>
<h2>防止表单重复提交</h2>
<form action="${pageContext.request.contextPath}/token.do" method="post">
<input type="hidden" value="${token}" name="tokenValue"/>
用户名：<input type="text" name="username"/>
<input type="submit" value="提交" id="submit"/>
</form>
</body>
</html>
<?xml version="1.0" encoding="UTF-8"?> <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <servlet> <servlet-name>token</servlet-name> <servlet-class>com.jalja.token.UserServlet</servlet-class> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>token</servlet-name> <url-pattern>*.do</url-pattern> </servlet-mapping> </web-app>