Cookie 记录最后访问时间

package cn.gs.ly.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LastVisitTimeServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setContentType("text/html; charset=UTF-8");        
        
        PrintWriter out = resp.getWriter();
        out.print("您上次访问的时间是：");        
        //先获取cookie  再赋值
        Cookie [] co = req.getCookies();//所有 Cookie 对象的数组
        for(int i=0;co!=null&&i<co.length;i++){ //遍历cookie数组
            if("last_time".equals(co[i].getName())){//获取cookie名
                String value = co[i].getValue(); //获取cookie值
                long time = Long.parseLong(value); //转换cookie值类型
                out.println(new Date(time).toLocaleString());//显示cookie里的最后一次系统时间
            }
        }
        
        //先查看cookie的最后时间并显示。再获取现在系统当前时间   
        long time = System.currentTimeMillis();
        Cookie c = new Cookie("last_time",time+"");//构造带指定名称和值的 cookie。
        c.setMaxAge(30*24*60*60);//cookie存活时间
        c.setPath(req.getContextPath()); //在当前应用有效 s.setPath("/");
        resp.addCookie(c);//添加cookie
    }
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }
}