防止表单的重复提交

防止表单的重复提交

表单重复提交的原因:网络延迟,重新加载

表单重复提交的解决办法:前端js控制,后端用token+session来控制(增加程序的容错性)
1、前端用js来进行校验

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登陆页面title>
head>
<script type="text/javascript">
	var flag = false;//标识是否提交过.true代表已经提交,false代表没有提交
	function isSubmit(){
		if(flag){
			//已经提交过了
			return false;
		}else{
			//没有提交过,提交一次
			flag = true;
			return true;
		}
	}
script>
<body>
	<form action="/cookie-demo/loginServlet" method="post" onsubmit="return isSubmit();">
		用户: <input type="text" name="username"/>
		<input type="submit" value="登陆">
	form>
body>
html>

效果演示
防止表单的重复提交_第1张图片
2、后端通过token+session来进行校验,为了展示效果,展示去掉前端代码
一、前端代码

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登陆页面title>
head>
<body>
	<form action="/cookie-demo/loginServlet" method="post">
	<input type="hidden" name="token" value="${token }"/>
		用户: <input type="text" name="username"/>
		<input type="submit" value="登陆">
	form>
body>
html>

2、产生token令牌的servlet

/**
 * 通过UUID随机产生一个token令牌
 * @author 紫炎易霄
 */
@WebServlet("/tokenServlet")
public class TokenServlet extends HttpServlet{
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		//通过UUID生成token令牌,并转发到jsp中,存储到隐藏域里面
		String token = UUID.randomUUID().toString();
		HttpSession session = req.getSession();
		session.setAttribute("token", token);
		req.getRequestDispatcher("/login.jsp").forward(req, resp);
	}
}

3、处理用户请求的servlet

/**
 * 接收表单重复提交
 * @author 紫炎易霄
 */
@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet{
	
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		//防止乱码
		req.setCharacterEncoding("UTF-8");
		resp.setContentType("text/html;charset=utf-8");
		//接收页面传过来的参数
		String username = req.getParameter("username");
		String paramToken = req.getParameter("token");
		HttpSession session = req.getSession();
		String token = (String) session.getAttribute("token");
		if(token != null && token.equals(paramToken)){
			//移除session
			session.removeAttribute("token");
			//说明是第一次提交
			//休眠5秒钟
			try {
				System.out.println(username+"执行数据库插入操作!!!!");
				Thread.sleep(2000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			resp.getWriter().write("数据保存成功!");
		}else{
			resp.getWriter().write("您已经提交过了,请不要再重复提交!");
		}
		
	}
}

效果演示
防止表单的重复提交_第2张图片

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