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;/*** <p>Project: scl-cookie - AddCookie</p>* <p>Powered by scl On 2023-09-04 16:36:59</p>* <p>描述：<p>** @author 孙臣龙 [1846080280@qq.com]* @version 1.0* @since 17*/
@WebServlet("/addCookie")
public class AddCookie extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//创建CookieCookie cookie = new Cookie("meite","scl");//设置存活时间cookie.setMaxAge(60);//添加Cookieresp.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;/*** <p>Project: scl-cookie - GetCookie</p>* <p>Powered by scl On 2023-09-04 16:43:04</p>* <p>描述：<p>** @author 孙臣龙 [1846080280@qq.com]* @version 1.0* @since 17*/
@WebServlet("/getCookie")
public class GetCookie extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//获取CookieCookie[] 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CookieCookie cookie = new Cookie("meite","scl");//设置存活时间cookie.setMaxAge(60);//添加Cookieresp.addCookie(cookie);