通过session 怎么防止表单的重复提交!

1.在提交表单的时候使用隐藏域；

String tokenValue=new Date().getTime();

2.往session中添加一个随机值；

request.getSession().setAttribute("token",tokenValue);

3.在servlet中对隐藏域的值和session中的值作比较；

servlet 中

String tokenValue=request.getParameter("token");

String sessionToken=request.getSeesion().getAttribute("token");

if(sessionToken !=null && ressionToken.equals(tokenValue)){

　　request.getSession().removeAttribute("token");

}

 1 <%@ page import="java.util.Date" %><%--
 2   Created by IntelliJ IDEA.
 3   User: ty
 4   Date: 2017/4/12
 5   Time: 11:17
 6   To change this template use File | Settings | File Templates.
 7 --%>
 8 <%@ page contentType="text/html;charset=UTF-8" language="java" %>
 9 <htm/l>
10 <head>
11     <title>Title</title>
12 </head>
13 <body>
14 <%
15     String tokenValue=new Date().getTime()+"";
16     request.getSession().setAttribute("token",tokenValue);
17 %>
18 
19      <form action="<%=request.getContextPath()%>/token1" method="post">
20          <input type="hidden" name="token" value="<%=tokenValue%>" />
21          username:<input type="text" name="username"/> <br>
22                   <input type="submit" value="submit">
23 
24      </form>
25 </body>
26 </html>

package main.java.servlet;

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

/**
 * Created by ty on 2017/4/12.
 */
@WebServlet(name = "TokenProcessServlet",urlPatterns = "/token1")
public class TokenProcessServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        String username = request.getParameter("username");
        String tokenValue = request.getParameter("token");
        Object sessionToken = request.getSession().getAttribute("token");
        response.getWriter().print("sessionToken===="+sessionToken+">>>");
        System.out.println("tokenValue="+tokenValue);
        System.out.println("sessionToken="+sessionToken);
              if(sessionToken != null && sessionToken.equals(tokenValue)) {
                  request.getSession().removeAttribute("token");
                  response.sendRedirect(request.getContextPath()+"/successful.jsp");
              }else{
                  response.sendRedirect(request.getContextPath()+"/error1.jsp");
                  return ;
              }


    }

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

    }
}

通过session 怎么防止表单的重复提交!

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