渚漪Day16——JavaWeb 07【Cookie】

Cookie

• 客户端技术(req,resp)
• 记录上次访问的时间

import javax.servlet.http.Cookie;
import javax.servlet.ServletException;
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.text.DateFormat;
import java.text.SimpleDateFormat;
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 {
        resp.setContentType("text/html");
        resp.setCharacterEncoding("utf-8");

        PrintWriter out = resp.getWriter();

        Cookie[] cookies = req.getCookies();
        DateFormat format= new SimpleDateFormat("yyyy年MM月dd日 HH时mm分ss秒");
        int i;
        for (i = 0; i < cookies.length ; i++) {
            if(cookies[i].getName().equals("LastTime")){
                out.write("上次访问的时间:");
                Date date = new Date(Long.parseLong(cookies[i].getValue()));
                out.write(format.format(date));
                break;

            }
        }
        if(i==cookies.length)
            out.write("这是第一次访问");

        resp.addCookie(new Cookie("LastTime", String.valueOf(System.currentTimeMillis())));

    }

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

• 设置有效期

 Cookie cookie = new Cookie("LastTime", String.valueOf(System.currentTimeMillis()));
        cookie.setMaxAge(60*60*24);

        resp.addCookie(cookie);

• 清除有效期

Cookie cookie = new Cookie("LastTime","清除");
cookie.setMaxAge(0);

resp.addCookie(cookie);