使用cookie进行登录操作
要求：1、登录的账号是首次登录则显示成功登录；
2、登录的账号非首次登录则显示最后一次登录的时间。
由于技术有限，目前所作的是固定账户名相同的，并非采用数据库进行对比。
首先需要设置登录界面，login.jsp文件：
<%--
Created by IntelliJ IDEA.
User: TY
Date: 2022/8/17
Time: 13:54
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>
<form action="/homework" method="post" ><br>
用户名<input id="username" name="username" type="text" ><br>
密码 <input name="password" type="password"><br>
<button type="submit">提交</button>
</form>
<%--<span style="color:red"></span>--%>
<span style="width: auto">${sessionScope.msg}</span>
</body>
</html>
然后可以设置一个登陆成功界面进行跳转，success.jsp：
<%--
Created by IntelliJ IDEA.
User: TY
Date: 2022/8/17
Time: 14:38
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>
<h1>成功登录</h1>
</body>
</html>
然后对主要文件cookie.java进行书写：
package com.hqyj.gwr.homework;
import com.sun.applet2.AppletParameters;
import com.sun.org.apache.bcel.internal.generic.IF_ACMPEQ;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.xml.crypto.Data;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.text.SimpleDateFormat;
import java.util.Date;
@WebServlet("/homework")
public class homework extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String encode = URLEncoder.encode("password", "UTF-8");
String username=request.getParameter("username");
String password=request.getParameter("password");
Cookie cookie = new Cookie("password", encode);
//将cookie放在响应中传入浏览器
response.addCookie(cookie);
Cookie username1= new Cookie("username", "123456");
response.addCookie(username1);
Date date = new Date();
String s = date.toString();
System.out.println(s);
Cookie[] cookies = request.getCookies();
for (Cookie c:cookies){
String name = c.getName();
String value = c.getValue();
//对拿到的cookie进行解码
String decode = URLDecoder.decode(value,"UTF-8");
response.setContentType("text/html;charset=utf-8");//固定写法
}
if ("zhangsan".equals(username)){
Date d= new Date();
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String now = df.format(d);
PrintWriter writer = response.getWriter();
writer.print("上次您登录的时间是："+now);
}else{
request.getRequestDispatcher("/success.jsp").forward(request,response);
}
}}
cookie存储的东西只能是字符串并且大小有限制；获取数据的方法与数组类似。