JavaWeb会话技术详解与案例

  Cookie[] cookies = req.getCookies(); //创建cookie对象，获得浏览器所有的cookie数组

        Cookie cookie = CookieUtils.findCookie(cookies,"lasttime");//通过：cookies:一个名称“lasttime”，找到数组里面对应的cookies,返回这个cookie:值
        

  Cookie  c = new Cookie("lasttime", wer); //创建一个cookie，
  名称为：lasttime，值为：wer变量对应的值

          resp.addCookie(c); //在浏览器添加：增加这个名称的cookie值，
          可以

package com.example.demo16;

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

public class HelloServlet4 extends HttpServlet {

    @Override
    public void init() throws ServletException {
        super.init();

        this.getServletContext().setAttribute("name","张三");
    }

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

        Cookie[] cookies = req.getCookies();

        Cookie cookie = CookieUtils.findCookie(cookies,"lasttime");

        System.out.println(cookie);
        if (cookie==null) {
            resp.setCharacterEncoding("utf-8");
            resp.setContentType("text/html;charset=UTF-8");
            resp.getWriter().println("<h1>您好，欢迎来到本网站！</h1>");


        } else {

resp.setCharacterEncoding("utf-8");
            resp.setContentType("text/htm/UTF-8");
            resp.getWriter().println("你上一次访问时间是:");  //出现了中文错误
            cookie = CookieUtils.findCookie(cookies, "lasttime");
            String value = cookie.getValue();

            resp.getWriter().println(value);

            Date d = new Date();  //变化的
           SimpleDateFormat sc=new SimpleDateFormat("yyyy-MM-dd-HH:mm:ss");

          String wer=sc.format(d);  //字符串

          System.out.println(wer);

 //其实就是要设置：时间，时间值为java， 变化的时间
          //  Cookie c = new Cookie("lasttime","11111"); 这个可以显示
           // Cookie c = new Cookie("lasttime","1-1-1-1-1");
          //  Cookie c = new Cookie("lasttime","2021-11-14");//2021-11-14 20:14不能反映，中文也不能
          //  Cookie c = new Cookie("lasttime","2021:11:14");// 空格不行

          Cookie  c = new Cookie("lasttime", wer);

          resp.addCookie(c);

        }

/*resp.getWriter().println("helloworld");

resp.setStatus(302);
//resp.setHeader("Location","/demo16_war/helloo");


resp.setHeader("Refresh","5,url=/demo16_war/helloo");

*/
        //    String name= (String) this.getServletContext().getAttribute("name");
        // System.out.println(name);
//text();

text();
    }

    protected void text() throws IOException {

        //Properties properties=new Properties();//创建文件对象
        //InputStream is=this.getServletContext().getResourceAsStream("WEB-INF/dp.properties");//这里的路径，

        //  properties.load(is);
//String driverClassName=properties.getProperty("driverClassName");
        // String url=properties.getProperty("url");
        //String  password=properties.getProperty("password");
        //  String usernane=properties.getProperty("username");

        //  System.out.println(driverClassName);
//System.out.println(url);
//System.out.println(password);
//System.out.println(usernane);

        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        try {
            Date d = sdf.parse(toString());
            System.out.println(d);
        } catch (ParseException e) {
            e.printStackTrace();

        }

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

package com.example.demo16;

import javax.servlet.http.Cookie;

public class CookieUtils {

    public static Cookie findCookie(Cookie[] cookies, String name){

        if(cookies==null){
            return null;

        }else {
            for(Cookie cookie:cookies){

if(name.equals(cookie.getName())) {  //找到相等的name名称

    return cookie;
}

            }

            return null;

        }}}

  String werr="我是谁";


          Cookie  c = new Cookie("lasttime", werr);

          resp.addCookie(c);

  resp.setContentType("text/html;charset=UTF-8");
   resp.getWriter().println("<h1>你上一次访问时间是:</h1>");