Cookie 登录时间 中文编码转换

会话

用cookie实现了一个登录的时间

package com.kevin.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;

/**
 * @program: javaweb-session-cookie
 * @author: 解城文 梧州学院软件开发中心
 * @create: 2021-10-31 19:07
 **/
//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，你来的时间，把这个时间封装成成一个新建，你下次带来，我就知道你来了

        //解决中文乱码
        resp.setContentType("text/html");
        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){
    
    
            //如果存在怎么办
            out.write("你上一次访问的时间是");
            for (int i = 0; i < cookies.length; i++) {
    
        //在这里使用itar 回车生成for的快捷键
                Cookie cookie = cookies[i];
                //获取cookie的名字
                if (cookie.getName().equals("lastLoginTime")){
    
    
                    //获取cookie的值
                    String value = cookie.getValue();
                    long lastLoginTime = Long.parseLong(cookie.getValue());  //将字符串变为时间戳 转为long 在转为date
                    Date date = new Date(lastLoginTime);
                    out.write(date.toLocaleString());
                }
            }
    }else{
    
    
            out.write("这是您第一次访问本站");
        }
        //服务器给客户端响应一个cookie
        Cookie cookie = new Cookie("lastLoginTime", System.currentTimeMillis()+"");
        resp.addCookie(cookie);
    }

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

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns="http://java.sun.com/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
                      http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
         version="3.0"
         metadata-complete="true">
    <servlet>
        <servlet-name>CookieDemo01</servlet-name>
        <servlet-class>com.kevin.servlet.CookieDemo01</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>CookieDemo01</servlet-name>
        <url-pattern>/c1</url-pattern>
    </servlet-mapping>
</web-app>

即使浏览器关闭了，cookie依然存在，

Cookie

1.从请求中拿到cookie信息

Cookie[] cookies = req.getCookies();  //获得cookie
cookie.getName() //获得cookie中的key
cookie.getValue(); //获得value的值
Cookie cookie = new Cookie("lastLoginTime", System.currentTimeMillis()+"");  //新建一个cookie的值
cookie.setMaxAge(24*60*60);   //设置cookie的有效期为一天
resp.addCookie(cookie); //响应给客户端一个cookie    

2.服务器响应给客户端cookie
cookie：一般都会保存在本地的用户目录下 appdata C:\Users\Alex\AppData
一个网站cookie是否存在上限！

public class CookieDemo02 extends HttpServlet {
    
    
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
    

        Cookie cookie = new Cookie("lastLoginTime", System.currentTimeMillis()+"");
        cookie.setMaxAge(0);  //cookie有效期为一天
        resp.addCookie(cookie);
    }
}

package com.kevin.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.net.URLDecoder;
import java.net.URLEncoder;
import java.util.Date;

/**
 * @program: javaweb-session-cookie
 * @author: 解城文 梧州学院软件开发中心
 * @create: 2021-11-01 11:21
 **/
//中文数据传递
public class CookieDemo03 extends HttpServlet {
    
    
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
    
        //Cookie,服务器端从客户端获取
        resp.setContentType("text/html;charset=utf-8");
        req.setCharacterEncoding("utf-8");
        resp.setCharacterEncoding("utf-8");
        Cookie[] cookies = req.getCookies();//这里返回数组，说明cookie可能存在多个

        PrintWriter out = resp.getWriter();
        //判断cookie是否存在
        if(cookies != null){
    
    
            //如果存在怎么办
            out.write("你上一次访问的时间是");
            for (int i = 0; i < cookies.length; i++) {
    
        //在这里使用itar 回车生成for的快捷键
                Cookie cookie = cookies[i];
                //获取cookie的名字
                if (cookie.getName().equals("lastLoginTime")){
    
    
                    //System.out.println(cookie.getValue());
                    URLDecoder.decode(cookies.getValue(),"utf-8");    //解码
                }
            }
        }else{
    
    
            out.write("这是您第一次访问本站");
        }
        Cookie cookie = new Cookie("name",URLEncoder.encode("解城文","utf-8"));  //编码
        resp.addCookie(cookie);
    }

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