cookie實作頁面顯示上次訪問時間

cookie實作頁面顯示上次訪問時間

1.代碼分析

package cn.bytedance.showtime;

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;

/**
 * Created with IntelliJ IDEA.
 *
 * @Auther: 這是靚仔呀
 * @Date: 2020/12/04/10:53 下午
 * @Description: a demo for showing time
 */

@WebServlet("/TimeTeller")
public class TimeTeller extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //設定contentType編碼，獲得cookies物件
        resp.setContentType("text/html;charset=utf-8");
        Cookie[] cookies = req.getCookies();
        //定義標識位，作用：自己看代碼悟
        boolean flag = true;
        if (cookies != null && cookies.length != 0){
            for (Cookie cookie : cookies) {
                String name = cookie.getName();
                if ("lastTime".equals(name)){
                    flag = false;
                    //獲取lastTime的value值，URLDecoder解碼后顯示在頁面上
                    String value = cookie.getValue();
                    System.out.println("解碼前:"+value);
                    value = URLDecoder.decode(value,"utf-8");
                    System.out.println("解碼后:"+value);
                    resp.getWriter().println("<h4>歡迎回來，你上次訪問時間是:</h4>"+value);

                    //修改cookie的新值
                    SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
                    String str_date = simpleDateFormat.format(new Date());
                    System.out.println("編碼前:"+str_date);
                    str_date = URLEncoder.encode(str_date, "utf-8");
                    System.out.println("編碼后:"+str_date);
                    //修改cookie的值和生命周期，發送cookie
                    cookie.setValue(str_date);
                    cookie.setMaxAge(60*60*24);
                    resp.addCookie(cookie);

                }
            }
        }

        if (cookies == null || cookies.length ==0 || flag){
            resp.getWriter().println("當前你是首次訪問頁面..");
            //創建cookie物件，并且將cookie保存到客戶端
            Cookie cookie = new Cookie("lastTime","");
            //時間格式化
            SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
            String str_date = simpleDateFormat.format(new Date());

            System.out.println("編碼前:"+str_date);
            //對str進行URLEncoder編碼，因為cookie的value不可以有特殊字符，比如空格
            str_date = URLEncoder.encode(str_date, "utf-8");
            System.out.println("編碼后:"+str_date);
            //修改cookie的值和生命周期，發送cookie
            cookie.setValue(str_date);
            cookie.setMaxAge(60*60*24);
            resp.addCookie(cookie);
        }
    }

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

2.效果展示
a.第一次訪問頁面時

b.重繪后

c.在瀏覽器中查看cookie資訊

3.總結

勉勉強強