出現表單重復提交的三種情況：
一、服務器響應緩慢，用戶多次點擊提交按鈕。
二、提交成功後刷新頁面。
三、提交成功後返回表單頁面再次點擊提交。
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();//創建令牌
System.out.println("在FormServlet中生成的token："+token);
request.getSession().setAttribute("token", token); //在服務器使用session保存token(令牌)
request.getRequestDispatcher("/index.jsp").forward(request, response);//跳轉到form.jsp頁面
}
if(path.equals("token.do")){
String name=request.getParameter("username");
String tokenValue=request.getParameter("tokenValue");//獲取客戶端的Token
System.out.println("獲取客戶端的token："+tokenValue);
String server_token = (String) request.getSession().getAttribute("token");//獲取服務器端的token
if(tokenValue!=null && server_token!=null && server_token.equals(tokenValue)){
System.out.println("處理請求; 獲得name==》"+name);
try {
Thread.sleep(3*1000);//模擬網絡延遲
} catch (InterruptedException e) {
e.printStackTrace();
}
}else{
System.out.println("不處理");
}
request.getSession().removeAttribute("token");//每次處理玩請求都要移除掉token
}
}
}
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML>
<html>
<head>
<title>Form表單</title>
</head>
<body>
<h2>防止表單重復提交</h2>
<form action="${pageContext.request.contextPath}/token.do" method="post">
<input type="hidden" value="${token}" name="tokenValue"/>
用戶名：<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>
