JavaWeb之Cookie的简单使用！！！

什么是Cookie

Cookie:客户端会话技术，将数据保存到客户端，以后每次请求都携带Cookie数据进行访问

Cookie 数据存放在浏览器端(客户端)

创建Cookie

1.创建Cookie

Cookie cookie = new Cookie("key","value");

2.使用response响应Cookie给客户端（浏览器）

response.addCookie(cookie);

/*
 * Copyright (c) 2020, 2023,  All rights reserved.
 *
 */
package cn;
 
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.Cookie;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
 
import java.io.IOException;
import java.lang.annotation.Retention;
 
/**
 * 
Project: scl-cookie - AddCookie
 * 
Powered by scl On 2023-09-04 16:36:59
 * 
描述：
 *
 * @author 孙臣龙 [1846080280@qq.com]
 * @version 1.0
 * @since 17
 */
@WebServlet("/addCookie")
public class AddCookie extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //创建Cookie
        Cookie cookie = new Cookie("meite","scl");
        //设置存活时间
        cookie.setMaxAge(60);
        //添加Cookie
        resp.addCookie(cookie);
    }
}

3.获取Cookie

Cookie[] cookies = request.getCookies();
for(Cookie str : cookies){
System.out.println(str.getName()+str.getValue());
}

/*
 * Copyright (c) 2020, 2023,  All rights reserved.
 *
 */
package cn;
 
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.Cookie;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
 
import java.io.IOException;
 
/**
 * 
Project: scl-cookie - GetCookie
 * 
Powered by scl On 2023-09-04 16:43:04
 * 
描述：
 *
 * @author 孙臣龙 [1846080280@qq.com]
 * @version 1.0
 * @since 17
 */
@WebServlet("/getCookie")
public class GetCookie extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取Cookie
        Cookie[] cookies = req.getCookies();
        for(Cookie  str : cookies){
            System.out.println(str.getName()+str.getValue());
        }
    }
}

Cookie过期时间

setMaxAge(int seconds):设置Cookie存活时间

1.正数：将Cookie写入浏览器所在的电脑硬盘，持久化存储，到期自动删除 

2.负数：默认值，Cookie存储在浏览器内存中，当浏览器关闭，内存释放，则Cookie被销毁。

3.零：删除对应Cookie

 //创建Cookie
        Cookie cookie = new Cookie("meite","scl");
        //设置存活时间
        cookie.setMaxAge(60);
        //添加Cookie
        resp.addCookie(cookie);