防止重复提交demo

时间：2023-12-31 10:31:14

利用session防止重复提交

思路：

前端控制：在点击提交按钮后设置按钮不可用。

后台控制：利用session，在初次进入表单页面的时候前生成一个随机token，将token保存到session并返回到前端页面，前端提交页面，后台获取前端提交的token值与session中的token比较。

主要代码：

package servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import servlet.token.TokenProccessor;

public class FormServlet extends HttpServlet{

    private static final long serialVersionUID = 1L;

    @Override

    protected void doGet(HttpServletRequest req, HttpServletResponse resp)

            throws ServletException, IOException {

        // 生成token

        String token = TokenProccessor.getInstance().makenToken();

        System.out.println("FormServlet中生成的token:" + token);

        req.getSession().setAttribute("token", token);

        // 进入表单提交页面

        req.getRequestDispatcher("/form.jsp").forward(req, resp);

    }

    @Override

    protected void doPost(HttpServletRequest req, HttpServletResponse resp)

            throws ServletException, IOException {

        this.doGet(req, resp);

    }

}

处理提交的Servlet

package servlet;

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{

    private static final long serialVersionUID = 1L;

    @Override

    protected void doGet(HttpServletRequest req, HttpServletResponse resp)

            throws ServletException, IOException {

        req.setCharacterEncoding("UTF-8");

        // 判断是否重复提交

        boolean b = isRepeatSubmit(req);

        if (true == b) {

            System.out.println("重复提交");

            return ;

        }

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

        System.out.println("处理请求!");

        String userName = req.getParameter("username");

        try {

            // 模拟系统处理

            Thread.sleep(3*1000);

        } catch (InterruptedException e) {

            e.printStackTrace();

        }

        System.out.println("插入数据:"+userName);

    }

    private boolean isRepeatSubmit(HttpServletRequest req) {

        String client_token = req.getParameter("token");

        // 用户提交表单时不存在token 表示直接刷新页面重复提交

        if (client_token == null) {

            return true;

        }

        // 返回后再次提交,当前用户不存在token重复提交

        String server_token = (String) req.getSession().getAttribute("token");

        if(server_token==null){

            return true;

        }

        // Session中令牌与表单提交不一致 重复提交

        if (!client_token.equals(server_token)) {

            return true;

        }

        return false;

    }

    @Override

    protected void doPost(HttpServletRequest req, HttpServletResponse resp)

            throws ServletException, IOException {

        this.doGet(req, resp);

    }

}

页面

<%@ 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="${pageContext.request.contextPath }/DoFormServlet" method="post">

        <%-- <input type="hidden" name="token" value="<%=session.getAttribute("token")%>"> --%>

        用户名:<input type="text" name="username">

        <input type="hidden" name="token" value="${token }">

        <input type="submit" value="提交" id="submit">

    </form>

</body>

<script type="text/javascript">

    function doSubmit(){

        var btnSubmit = document.getElementById("submit");

        btnSubmit.disabled="disabled";

        return true;

    }

</script>

</html>

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