JavaWeb_Cookie-优快云博客

本文链接：https://blog.youkuaiyun.com/king_xbstudy/article/details/124210715

本文档展示了如何使用Java Servlet通过Cookie来记录用户的上一次访问时间，包括获取Cookie、设置有效期及处理中文编码。

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cookie

1.Java

package com.xb.servlet;

import javax.servlet.ServletException;
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.PrintWriter;
import java.util.Date;

//保存用户上一次访问的时间
public class CookieDemo01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //服务器，告诉你来的时间，把这个时间封装成一个信件，下次来，就晓得你来了

        //解决中文乱码
        req.setCharacterEncoding("utf-8");
        resp.setCharacterEncoding("utf-8");


        PrintWriter out = resp.getWriter();

        //Cookie，服务器端从客户端获取
        Cookie[] cookies = req.getCookies();//这里返回数组，说明Cookie可能存在多个

        //判断Cookie是否存在
        if (cookies!=null){
            //存在
            out.write("你上一次访问的时间:");
            for (int i = 0; i < cookies.length; i++) {
                Cookie cookie = cookies[i];
                //获取cookie的名字
                if (cookie.getName().equals("lastLoginTime")){
                    //获取Cookie的值
                    cookie.getValue();
                    long lastLoginTime = Long.parseLong(cookie.getValue());
                    Date date = new Date(lastLoginTime);
                    out.write(date.toLocaleString());
                }
            }
        }else {
            out.write("这是您第一次访问");
        }

        //服务器给客户端响应一个cookie
        Cookie cookie = new Cookie("lastLoginTime", System.currentTimeMillis()+"");
        //设置cookie有效期1天
        cookie.setMaxAge(24*60*60);
        resp.addCookie(cookie);


    }

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

2.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
                            http://xmlns.jcp.rog/xml/ns/javaee/web-app_4_0.xsd"
        version="4.0"
        metadata-complete="true">

    <servlet>
        <servlet-name>CookieDemo01</servlet-name>
        <servlet-class>com.xb.servlet.CookieDemo01</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>CookieDemo01</servlet-name>
        <url-pattern>/c1</url-pattern>
    </servlet-mapping>
</web-app>