image.png

一、Cookie

（1）Cookie 基本使用

image.png

发送 cookie

package com.test.web;

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;

// 发送cookie demo
@WebServlet("/servletSetCookie")
public class ServletSetCookie extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp){
        // 创建cookie对象
        Cookie cookie = new Cookie("myCookie", "123123");
        // 发送cookie
        resp.addCookie(cookie);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp){
        this.doGet(req, resp);
    }
}

获取cookie

package com.test.web;

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;

// 获取 cookie demo
@WebServlet("/servletGetCookie")
public class ServletGetCookie extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp){
        Cookie[] cookies = req.getCookies();
        for (Cookie cookie : cookies) {

            String name = cookie.getName();
            if (name.equals("myCookie")) {
                System.out.println("成功获取到之前设置的cookie " + name + ":" + cookie.getValue());
                break;
            }
        }
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp){
        this.doGet(req, resp);
    }
}

（2）Cookie 原理

image.png

设置cookie：后端服务通过 set-cookie:username=zs 响应头来告知浏览器创建一个名为username，值为zs的 cookie
获取cookie：后端服务接收这次请求时，在请求头 cookie 里面获取的所有cookie

（3）Cookie 细节

image.png

二、Session

（1）Session 基本使用

image.png

存储 Session

package com.test.web.session;

import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;

@WebServlet("/servletSetSession")
public class ServletSetSession extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp){
        // 获取session对象
        HttpSession session = req.getSession();
        // 设置session
        session.setAttribute("username", "张三");
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp){
        this.doGet(req, resp);
    }
}

获取 Session

package com.test.web.session;

import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

@WebServlet("/servletGetSession")
public class ServletGetSession extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp){
        // 获取session对象
        HttpSession session = req.getSession();
        Object username = session.getAttribute("username");
        System.out.println("成功获取存储的 username:" + username);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp){
        this.doGet(req, resp);
    }
}