Cookie

HTTP Cookie（也叫 Web Cookie 或浏览器 Cookie）是服务器发送到用户浏览器并保存在本地的一小块数据，它会在浏览器下次向同一服务器再发起请求时被携带并发送到服务器上。通常，它用于告知服务端两个请求是否来自同一浏览器，如保持用户的登录状态。

会话跟踪技术

原理图

Cookie

Cookie基本使用

创建web项目

1. 创建webapp骨架项目
2. 导入pom.xml坐标
3. 创建java和resources目录

发送Cookie案例

编写Servlet

package com.taotao.web;
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;
/**
 * create by 刘鸿涛
 * 2022/4/1 13:29
 */
@WebServlet("/aServlet")
public class AServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //发送Cookie
        //1.创建Cookie对象         键、对值
        Cookie cookie = new Cookie("username","taotao");
        //2.发送Cookie，response
        resp.addCookie(cookie);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

运行测试-发送Cookie

得到Cookie案例

编写Servlet

package com.taotao.web;
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;
/**
 * create by 刘鸿涛
 * 2022/4/1 13:29
 */
@WebServlet("/bServlet")
@SuppressWarnings({"all"})
public class BServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取Cookie
        //获取Cookie数组
        Cookie[] cookies = req.getCookies();
        //遍历数组
        for (Cookie cookie: cookies) {
            //获取数据
            String name = cookie.getName();
            if("username".equals(name)){
                String value = cookie.getValue();
                System.out.println(name + " :" + value);
            }
            break;
        }
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

运行测试-获取Cookie

:::info 先访问aServlet发送cookie ::: :::info 访问bServlet得到发送的cookie :::

Cookie原理

响应头set-cookie

Cookie使用细节

cookie存活时间

:::info 设置cookie存活时间，可以让cookie驻留在电脑硬盘上 :::

编写aServlet

package com.taotao.web;
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;
/**
 * create by 刘鸿涛
 * 2022/4/1 13:29
 */
@WebServlet("/aServlet")
public class AServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //发送Cookie
        //1.创建Cookie对象         键、对值
        Cookie cookie = new Cookie("username","taotao");
        //设置cookie的存活时间 1周7天
        cookie.setMaxAge(60*60*24*7);   //单位为秒s
        //2.发送Cookie，response
        resp.addCookie(cookie);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

运行测试

:::info 先访问aServlet，然后关闭浏览器 ::: :::info 再次打开浏览器，访问bServlet，发现可以得到cookie :::

查看电脑硬盘存在的cookie

Cookie存储中文

默认存储中文报错

进行转码：URL编码

package com.taotao.web;
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;
import java.net.URLEncoder;
/**
 * create by 刘鸿涛
 * 2022/4/1 13:29
 */
@WebServlet("/aServlet")
public class AServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //发送Cookie
        //1.创建Cookie对象         键、对值
        String value = "涛涛";
        //URL编码
        value = URLEncoder.encode(value, "UTF-8");
        System.out.println("存储数据：" + value);
        Cookie cookie = new Cookie("username",value);
        //设置cookie的存活时间 1周7天
        cookie.setMaxAge(60*60*24*7);   //单位为秒s
        //2.发送Cookie，response
        resp.addCookie(cookie);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

测试运行

进行解码：UT8-8

package com.taotao.web;
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;
import java.net.URLDecoder;
/**
 * create by 刘鸿涛
 * 2022/4/1 13:29
 */
@WebServlet("/bServlet")
@SuppressWarnings({"all"})
public class BServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取Cookie
        //获取Cookie数组
        Cookie[] cookies = req.getCookies();
        //遍历数组
        for (Cookie cookie: cookies) {
            //获取数据
            String name = cookie.getName();
            if(name.equals("username")){
                String value = cookie.getValue();
                //URL解码
                value = URLDecoder.decode(value, "UTF-8");
                System.out.println(name + " :" + value);
                break;
            }
        }
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

测试运行

Cookie自我理解

cookie的实现是基于HTTP协议的
学了这个cookie，感觉可有意思，还可以设置生命周期
感觉这个cookie中插入点木马病毒，应该也是可以的，
也就是说，只要你们用完浏览器不清除某个站点请求的cookie，那么，那个站点就有可能攻击你