[Untitled] Use cookies to display the user's last visit time

Create a new web project in idea, add the servlet-api.jar package, and create a servlet class of LastServlet in the src package of the project. This class is used to obtain the time in the cookie information and send it to the client.

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.net.URLDecoder;
import java.net.URLEncoder;
import java.text.SimpleDateFormat;
import java.util.Date;

@WebServlet(name = "LastAccessServlet",urlPatterns = "/LastAccessServlet")
public class LastAccessServlet extends HttpServlet {
    
    
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    
        //指定服务器输出的内容为UTF-8，防止乱码
        response.setContentType("text/html;charset=utf-8");
        //获取所有cookie
        Cookie[] cookies=request.getCookies();
        //定义flag的boolean变量，用于判断cookies是否为空
        boolean flag=false;
        //遍历数组，增强for循环
        if (cookies.length>0&&cookies!=null){
    
    
            for (Cookie cookie:cookies) {
    
    
                //获取cookie的名称
                String name = cookie.getName();
                //判断名称是否是lastTime
                if ("lastTime".equals(name)){
    
    
                    //该cookie不是第一次访问
                    flag=true;
                    //响应数据
                    //获取cookie的value
                    String value=cookie.getValue();
                    System.out.println("解码前："+value);
                    //URL解码
                    value= URLDecoder.decode(value,"utf-8");
                    System.out.println("解码后"+value);
                    response.getWriter().write("欢迎回来，您上次访问的时间是"+value);
                    //设置cookie的value
                    //获取当前时间的字符串，重新设置cookie的值，重新发送cookie
                    Date date=new Date();
                    SimpleDateFormat timesdf=new SimpleDateFormat("yyyy年MM月dd日“+”HH:mm:ss");
                    String str_time=timesdf.format(date);
                    System.out.println("编码前："+str_time);
                    //URL编码
                    str_time= URLEncoder.encode(str_time,"utf-8");
                    System.out.println("编码后："+str_time);
                    //设置cookie存活时间
                    cookie.setMaxAge(60*60*24*30);
                    //加入当前的cookie请求时间
                    response.addCookie(cookie);
                    break;
                }
            }
            //如果cookies中没有时间，也就是没有访问过
            if (cookies==null||cookies.length==0||flag==false){
    
    
                //设置cookie的value
                //获取当前的时间的字符串，重新设置cookie的值，重新发送cookie
                Date date=new Date();
                SimpleDateFormat sdf=new SimpleDateFormat("yyyy年MM月dd日“+”HH:mm:ss");
                String str_date=sdf.format(date);
                System.out.println("编码前："+str_date);
                //URL编码
                str_date=URLEncoder.encode(str_date,"utf-8");
                System.out.println("编码后："+str_date);
                Cookie cookie=new Cookie("lastTime",str_date);
                //设置cookie存活时间
                cookie.setMaxAge(60*60*24*30);
                response.addCookie(cookie);
                response.getWriter().write("您好。欢迎首次访问");
            }
        }
    }

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