Java：使用Cookie记录客户端浏览器上次访问时间

package cn.gpxxg.web.servlet;

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.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

@WebServlet("/servletCookieDemo03")
public class ServletCookieDemo03 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");

        // 1、设置返回的格式
        response.setContentType("text/html;charset=utf-8");

        boolean flag = false;
        Cookie[] cookies = request.getCookies();
        for (Cookie cookie : cookies) {
            String name = cookie.getName();
            if ("lastTime".equals(name))
            {
                // 找到了lastTime的cookie，获取值
                flag = true;
                String value = cookie.getValue();
                System.out.println("解码前：" + value);
                value = URLDecoder.decode(value, "utf-8");
                System.out.println("解码后：" + value);

                // 设置新的cookie,记录最新的时间
                setLastTime(response, cookie);

                // 输出到页面上
                response.getWriter().write("<h1>欢迎回来，您上次的时间为" + value + "<h1>");
                break;
            }
        }

        if (flag == false)
        {
            // 如果是一次来，提示欢迎新客户来，希望有一个好的购物体验

            // 1、设置返回的格式
            response.setContentType("text/html;charset=utf-8");

            // 2、记录当前时间到cookie，发送到客户端浏览器
            this.setLastTime(response, null);

            // 3、返回内容
            response.getWriter().write("<h1>欢迎新客户来，希望有一个好的购物体验</h1>");
        }

    }

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

    public void setLastTime(HttpServletResponse response, Cookie cookie1) throws UnsupportedEncodingException {

        // 如果是lastTime的cookie,删除掉重新赋值
        if (cookie1 != null && "lastTime".equals(cookie1.getName()))
            cookie1.setMaxAge(0);

        // 时间格式
        Date date = new Date();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH时mm分ss秒");
        String format = sdf.format(date);
        System.out.println("编码前：" + format);
        format = URLEncoder.encode(format, "utf-8");
        System.out.println("编码后：" + format);

        // 设置coolkie为当前时间
        Cookie cookie = new Cookie("lastTime", format);
        System.out.println(cookie);

        // 设置cookie的有效时间为1天
        cookie.setMaxAge(86400);

        response.addCookie(cookie);

    }
}