javaweb之每次访问的时候都在浏览器上返回上次访问的时间，原码

package tools;

import javax.servlet.http.Cookie;

public class Cookiechoose {

	public static Cookie CookiegetCookieByName(Cookie[] cookies,String cookieName) {
		if(cookies==null) {
			return null;
		}else {
			for(Cookie cookie:cookies) {
				if(cookie.getName().equals(cookieName)) {
					return cookie;
				}
			}
			return null;
		}
	}

}

package cn.itcast.servlet;

import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

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 tools.Cookiechoose;

/**
 * Servlet implementation class Time
 */
@WebServlet("/Time")
public class Time extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public Time() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//获取所有的cookie，化为一个数组
		Cookie[] cookies=request.getCookies();
		//通过自己构建的工具类来选出特定名字的cookie，这里设置的名字是last
		Cookie cookie=Cookiechoose.CookiegetCookieByName(cookies, "last");
		//创建一个date对象，按照Format将其改为字符串
		Date date=new Date();
		SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		String sDate=sdf.format(date);
		//如果获取的为空，则是第一次访问
		if(cookie==null) {
			//在页面上打上welcome
			response.getWriter().print("welcome");
			//第一次，所以要创建一个cookie对象，名字起为last，值为当前的时间
			Cookie c=new Cookie("last",sDate);
			//设置cookie的声明周期，0则是每次回话结束后就消失，60*60则是一小时，里面的单位是秒
			c.setMaxAge(60*60);
			//将这个cookie返回给客户端浏览器
			response.addCookie(c);
		}else {
			//这里代表第二次访问，获取以前的时间并打印出来
			String lasttime=cookie.getValue();
			response.getWriter().print("lasttime:"+lasttime+"");
			//设置一个新的时间
			cookie.setValue(sDate);
			cookie.setMaxAge(60*60);
			response.addCookie(cookie);
		}
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}