Cookie

概念：客户端会话技术，将数据保存到客户端

浏览器会自动存储Cookie，下一次请求会自动带着Cookie

使用步骤

　　1.创建Cookie对象，绑定数据（第一次请求）

new Cookie(String name,String value)

　　2. 发送Cookie对象（响应）

response.addCookie(Cookie cookie)

　　3.获取Cookie对象，拿到数据（第二次请求）

Cookie[] request.getCookie()

 内部使用map的结构来存储数据

package cn.itcast.cookie;

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 java.io.IOException;

/**
 * @author 旗木五五开
 * @create 2020-03-23 16:55
 * 快速入门
 */
@WebServlet("/cookieDemo1")
public class CookieDemo1 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//        1.创建Cookie对象
        Cookie c = new Cookie("msg", "hello");
//        2.发送Cookie(浏览器返回)
        response.addCookie(c);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}

package cn.itcast.cookie;

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 java.io.IOException;

/**
 * @author 旗木五五开
 * @create 2020-03-23 17:01
 */
@WebServlet("/cookieDemo2")
public class CookieDemo2 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//        3.获取Cookie
        Cookie[] cs = request.getCookies();
//        获取数据，遍历Cookies
        if (cs!=null){
            for (Cookie c : cs) {
                String name = c.getName();
                String value = c.getValue();
                System.out.println(name+":"+value);
            }
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}

 

 这时候用其他浏览器访问demo2控制台上不会输出内容。因为cookie为空