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[Java教程]token防止表单重复提交

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>

<??> <web-app version="2.5"    ="http://java.sun.com/    ="http://www.w3.org/2001/    xsi:schemaLocation="http://java.sun.com/>   <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>