jsp 内置对象登录 cookie + session

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概述
一共两个页面当直接访问产品列表的时候, 会判断用户是否登录, 如果用户没有登录, 则直接 3 秒跳转. 如果用户登录, 则不进行跳转登录页面: 对于登录页面来说, 直接输入用户名, 密码. 和数据库进行对比, 进行登录. 并进行密码的本地保存
ps 一般是需要对密码加密进行本地保存的
代码如下
配置文件
<!DOCTYPE web-app PUBLIC
“-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN”
“http://java.sun.com/dtd/web-app_2_3.dtd” >

<web-app>
<display-name>Archetype Created Web Application</display-name>
<servlet>
<servlet-name>login</servlet-name>
<jsp-file>/Login.jsp</jsp-file>
<init-param>
<param-name>driver</param-name>
<param-value>com.mysql.cj.jdbc.Driver</param-value>
</init-param>
<init-param>
<param-name>url</param-name>
<param-value>jdbc:mysql://47.94.95.84:32786/test</param-value>
</init-param>
<init-param>
<param-name>user</param-name>
<param-value>test</param-value>
</init-param>
<init-param>
<param-name>password</param-name>
<param-value>**</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>login</servlet-name>
<url-pattern>/login.html</url-pattern>
</servlet-mapping>
</web-app>

登录界面
<%@ page import=”java.sql.Connection” %>
<%@ page import=”java.sql.PreparedStatement” %>
<%@ page import=”java.sql.ResultSet” %>
<%@ page import=”java.sql.DriverManager” %><%–
Created by IntelliJ IDEA.
User: ming
Date: 19-3-13
Time: 下午 10:02
To change this template use File | Settings | File Templates.
–%>
<%@ page contentType=”text/html;charset=UTF-8″ language=”java” %>
<html>
<head>
<title> 登录页面 </title>
</head>
<form action=”./login.html” method=”post”>
<input type=”text” name=”username” id=”username”/>
<input type=”password” name=”password” id=”password”/>
<input type=”submit” value=”submit”/>
</form>
<script>
// js 脚本, 读取客户端的 cookie
let cookie = {};
let all = document.cookie;
let list = all.split(“;”);
for(let i = 0; i < list.length; i++){
let p = list[i].indexOf(“=”);
let space = list[i].indexOf(” “);
let name = list[i].substring(space + 1, p);
let value = list[i].substring(p+1);
value = decodeURIComponent(value);
cookie[name]=value;
}
// 填充到 value
if(cookie[“flage”] == “true”) {
document.getElementById(“username”).setAttribute(“value”, cookie[“user”]);
document.getElementById(“password”).setAttribute(“value”, cookie[“password”]);
}
</script>
<body>
<%
String dbdriver = config.getInitParameter(“driver”);
String dburl = config.getInitParameter(“url”);
String dbuser = config.getInitParameter(“user”);
String dbpassword = config.getInitParameter(“password”);
// 连接对象
Connection connection = null;
// 操作
PreparedStatement preparedStatement = null;
// 结果
ResultSet resultSet = null;
// 用户 id
String mid = null;
// 标志位
boolean falge = false;
try{
Class.forName(dbdriver);
// 获得连接
connection = DriverManager.getConnection(dburl, dbuser, dbpassword);
// 编写 sql 验证 ID 密码
String sql = “SELECT mid FROM member WHERE name = ? AND password = ?”;
// 实例化操作对象
preparedStatement = connection.prepareStatement(sql);
// 设置查询内容
preparedStatement.setString(1, request.getParameter(“username”));
preparedStatement.setString(2, request.getParameter(“password”));
// 执行查询
resultSet = preparedStatement.executeQuery();
// 如果可以查询到，表示合法用户
if(resultSet.next()){
mid = resultSet.getString(1);
// 修改标志位
falge = true;
}
}catch (Exception e){
e.printStackTrace();
}finally {
try{
resultSet.close();
preparedStatement.close();
connection.close();
}catch (Exception e){
e.printStackTrace();
}
}
// 判断是否登录成功
if(falge){
// 登录成功
// 保存 session 保存 cookie
session.setAttribute(“mid”, mid);
// 保存 cookie
Cookie cookieMid = new Cookie(“mid”, mid);
Cookie cookieUser = new Cookie(“user”, request.getParameter(“username”));
Cookie cookiePassword = new Cookie(“password”, request.getParameter(“password”));
// 增加登录态 cookie
Cookie cookieFlage = new Cookie(“flage”, “true”);
// 客户端增加 Cookie
response.addCookie(cookieMid);
response.addCookie(cookieUser);
response.addCookie(cookiePassword);
response.addCookie(cookieFlage);
// 设置定时跳转
response.setHeader(“refresh”, “3;URL=product.jsp”);
%>
登录成功即将跳转到首页产品界面
未跳转点击 <a hre=”./product.jsp”> 点击此处 </a>
<%
}else{
// 查询用户是否已经登录
if(session.getAttribute(“mid”) == null) {
Cookie cookieFlage = new Cookie(“flage”, “false”);
response.addCookie(cookieFlage);
}
}
%>
</body>
</html>

产品界面
<%–
Created by IntelliJ IDEA.
User: ming
Date: 19-3-14
Time: 下午 2:51
To change this template use File | Settings | File Templates.
–%>
<%@ page contentType=”text/html;charset=UTF-8″ language=”java” %>
<html>
<head>
<title>Title</title>
</head>
<body>
此为商品列表
<script>
// 判断当前登录态
// js 脚本, 读取客户端的 cookie
let cookie = {};
let all = document.cookie;
let list = all.split(“;”);
for(let i = 0; i < list.length; i++){
let p = list[i].indexOf(“=”);
let space = list[i].indexOf(” “);
let name = list[i].substring(space + 1, p);
let value = list[i].substring(p+1);
value = decodeURIComponent(value);
cookie[name]=value;
}
// 获取登录状态
if(cookie[“flage”] != “true”){
// 登录状态
alert(“ 请您登录 3 秒将会跳转 ”);
}
</script>
<%
// 服务器端验证
if(session.getAttribute(“mid”) == null) {
// 执行页面跳转
response.setHeader(“refresh”, “2;URL=/login.html”);
}
%>
</body>
</html>