10-客户端防表单重复提交和服务器端session防表单重复提交

/****************************************************DoFormServlet********************************************************/

package session;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class DoFormServlet extends HttpServlet {

   protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       /*String name = request.getParameter("user");
       try {
           Thread.sleep(1000*3);
       } catch (InterruptedException e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
       }
       //模拟向数据库注册用户
       System.out.println("向数据库注册用户");*/

       boolean b = isTokenValid(request);
       if(!b){
           System.out.println("请不要重复提交");
           return;
       }
       //在向数据库中提交之前要remove掉表单号
       request.getSession().removeAttribute("token");
       System.out.println("向数据库注册用户");

   }
   //判断表单号是否有效
   private boolean isTokenValid(HttpServletRequest request) {
       //得到客户机带过来的表单号
       String clientToken = request.getParameter("token");
       //判断客户机是否带表单号过来
       //如果没带过来，我也认为你是重复提交
       if(clientToken==null){
           return false;
       }

       //判断服务器里有没有表单号
       String serverToken = (String) request.getSession().getAttribute("token");
       //服务端里如果没有的话，也不行
       if(serverToken == null){
           return false;
       }
       //客户端和服务端不想等的话也不行
       if(!clientToken.equals(serverToken)){
           return false;
       }
       return true;
   }

   protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       doGet(request, response);
   }

}

/*********************************************************************************form.jsp***********************************************/

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
   <form action="/day07/DoFormServlet" method="post">
       <input type="hidden" name="token" value="${token}">
         用户名：<input type="text" name="username"><br>
         <input type="submit" value="提交">
   </form>
</body>
</html>

/****************************************************************DoFormServlet**************************************************************/