1. Cookie.setMaxAge(72460*60)
2. Cookie.setPath(“/day0X”);
3. Httpwatch观察
4. Cookie.setMaxAge(0)删除同名Cookie

import java.io.IOException;
import java.util.Date;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/*
 * http://localhost:8080/day07/Demo2?name=jack回车
 */
public class Demo2 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        String name = request.getParameter("name");
        if(name==null){
            name="default";
        }

        //取得客户端的所有Cookie的值
        Cookie[] cookies = request.getCookies();
        if(cookies==null){
            Cookie cookie = new Cookie("name_"+name,System.currentTimeMillis()+"");
            cookie.setMaxAge(1*24*60*60);
            response.addCookie(cookie);
            response.setContentType("text/html;charset=UTF-8");
            response.getWriter().write("欢迎"+name+"首次光临,访问时间：" + new Date().toLocaleString());
        }else{
            //查找名为name的Cookie
            Cookie nameCookie = null;
            for(Cookie c : cookies){
                if(c.getName().equals("name_"+name)){
                    nameCookie = c;
                    break;
                }
            }
            //找到了
            if(nameCookie!=null){
                String strTime = nameCookie.getValue();
                response.setContentType("text/html;charset=UTF-8");
                long lastTime = Long.parseLong(strTime);
                response.getWriter().write("欢迎"+name+"再次光临,你上次访问时间：" + new Date(lastTime).toLocaleString());
                //更新时间
                Cookie cookie = new Cookie("name_"+name,System.currentTimeMillis()+"");
                cookie.setMaxAge(1*24*60*60);
                response.addCookie(cookie);
            }
        }
    }
}