概念

客户端会话技术

快速入门

使用步骤

1、创建Cookie对象，绑定数据
2、发送Cookie对象
3、获取Cookie，拿到数据

package com.example.javawebs.cookiedemo;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
@WebServlet("/cookieServlet1")
public class cookieServlet1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //创建cookie对象
        Cookie c = new Cookie("msg", "hello");
        //设置cookie存活时间  将cookie持久化到硬盘 30秒  还有更多属性可以设置
        c.setMaxAge(30);
        //发送cookie
        response.addCookie(c);
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request,response);
    }
}

package com.example.javawebs.cookiedemo;
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;
@WebServlet("/cookieServlet2")
public class cookieServlet2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取cookie
        Cookie[] cs = request.getCookies();
        //获取数据，遍历cookie
        if (cs != null){
            for (Cookie c : cs) {
                String name = c.getName();
                String value = c.getValue();
                System.out.println(name+":"+value);
            }
        }
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request,response);
    }
}

多个Cookie

package com.example.javawebs.cookiedemo;
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;
@WebServlet("/cookieServlet3")
public class cookieServlet3 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //创建cookie对象
        Cookie c1 = new Cookie("msg", "hello");
        Cookie c2 = new Cookie("name", "lww");
        Cookie c3 = new Cookie("high", "180");
        //发送cookie
        response.addCookie(c1);
        response.addCookie(c2);
        response.addCookie(c3);
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request,response);
    }
}

Cookie 上次登录时间demo

package com.example.javawebs.cookiedemo;
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;
import java.net.URLEncoder;
import java.text.SimpleDateFormat;
import java.util.Date;
@WebServlet("/cookieServlet4")
public class cookieServlet4 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        Cookie[] cookies = request.getCookies();
        boolean flag = false; //没有cookie为lastTime
        if (cookies != null && cookies.length >0){
            for (Cookie cookie : cookies) {
                String name = cookie.getName();
                if ("lastTime".equals(name)){
                    String value = cookie.getValue();
                    value = URLDecoder.decode(value,"utf-8");
                    response.getWriter().write("欢迎回来,上次访问时间为："+value);
                    flag = true;
                    //美国时间，需要转为中国时间
                    Date date = new Date();
                    SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
                    String str_date = sdf.format(date);
                    str_date = URLEncoder.encode(str_date, "utf-8");
                    cookie.setValue(str_date);
                    cookie.setMaxAge(60*60*24*30);
                    response.addCookie(cookie);
                    break;
                }
            }
        }
        if (cookies==null || cookies.length==0 || flag==false){
            //美国时间，需要转为中国时间
            Date date = new Date();
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
            String str_date = sdf.format(date);
            str_date = URLEncoder.encode(str_date, "utf-8");
            Cookie cookie = new Cookie("lastTime", str_date);
            cookie.setMaxAge(60*60*24*30);
            response.addCookie(cookie);
            response.getWriter().write("欢迎首次登录");
        }
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request,response);
    }
}

JSP 完成上面demo

<%@ page import="java.util.Date" %>
<%@ page import="java.text.SimpleDateFormat" %>
<%@ page import="java.net.URLEncoder" %>
<%@ page import="java.net.URLDecoder" %>
<%--
  Created by IntelliJ IDEA.
  User: 77239
  Date: 2022/1/3
  Time: 23:34
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<%
    Cookie[] cookies = request.getCookies();
    boolean flag = false; //没有cookie为lastTime
    if (cookies != null && cookies.length >0){
        for (Cookie cookie : cookies) {
            String name = cookie.getName();
            if ("lastTime".equals(name)){
                flag = true;
                String value = cookie.getValue();
                value = URLDecoder.decode(value,"utf-8");
                //这里需要导入jsp api包，才可以使用out.write()
                response.getWriter().write("欢迎回来,上次访问时间为："+value);
                //美国时间，需要转为中国时间
                Date date = new Date();
                SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
                String str_date = sdf.format(date);
                str_date = URLEncoder.encode(str_date, "utf-8");
                cookie.setValue(str_date);
                cookie.setMaxAge(60*60*24*30);
                response.addCookie(cookie);
                break;
            }
        }
    }
    if (cookies==null || cookies.length==0 || flag==false){
        //美国时间，需要转为中国时间
        Date date = new Date();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
        String str_date = sdf.format(date);
        str_date = URLEncoder.encode(str_date, "utf-8");
        Cookie cookie = new Cookie("lastTime", str_date);
        cookie.setMaxAge(60*60*24*30);
        response.addCookie(cookie);
        response.getWriter().write("欢迎首次登录");
    }
%>
</body>
</html>