JSP改造Cookie案例以及Session的快速入门

<%@ page import="java.util.Date" %>
<%@ page import="java.text.SimpleDateFormat" %>
<%@ page import="java.net.URLEncoder" %>
<%@ page import="java.net.URLDecoder" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>itcast</title>
</head>
<body>

<%

    //1..获取所有的Cookie
    Cookie[] cookies = request.getCookies();
    boolean flag = false;//没有cookie为lastTime

    //2.遍历Cookie数组
    if (cookies != null && cookies.length > 0){
        for (Cookie cookie : cookies) {
            //3.获取cookie的名称
            String name = cookie.getName();
            //4.判断名称是否是：lastTime
            if ("lastTime".equals(name)){
                //有该cookie，不是第一次访问
                flag = true;//有lastTime的cookie
                //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 format = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");//更改为中国格式的时间
                String str_date = format.format(date);

                //URL编码
                System.out.println("编码前:"+str_date);
                str_date = URLEncoder.encode(str_date, "UTF-8");
                System.out.println("编码后:"+str_date);

                cookie.setValue(str_date);
                //设置cookie存活时间
                cookie.setMaxAge(60 * 60 * 24 * 30);//一个月

                response.addCookie(cookie);//发送cookie

                //响应数据
                //获取cookie的value，时间
                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);

%>

                <h1>欢迎回来，您上次访问时间为：<%=value%>></h1>

<%


                //找到直接停止
                break;
            }
        }
    }

    if (cookies == null || cookies.length == 0 || flag == false ){
        //没有，第一次访问

        //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 format = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");//更改为中国格式的时间
        String str_date = format.format(date);

        //URL编码
        System.out.println("编码前:"+str_date);
        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);//一个月
        response.addCookie(cookie);//发送cookie

%>
        <h1>您好，欢迎您首次访问</h1>
<%
    }
%>
</body>
</html>

Session的快速入门

概念：服务器端会话技术，在一次会话的多次请求间共享数据，将数据保存在服务器端的对象中，HttpSession

快速入门：

　　1.获取Session对象

HttpSession session = request.getSession();

　　2.使用HttpSession对象:

　　　　Object getAttribute(String name)

　　　　void setAttribute(String name,Object value)

　　　　void removeAttribute(String name)

session存储数据：

@WebServlet(name = "SessionDemo1", value = "/SessionDemo1")
public class SessionDemo1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //使用Session共享数据

        //1.获取session
        HttpSession session = request.getSession();
        //2.存储数据
        session.setAttribute("msg", "hello session");
    }
}

session获取数据

@WebServlet(name = "SessionDemo2", value = "/SessionDemo2")
public class SessionDemo2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //使用Session共享数据

        //1.获取session
        HttpSession session = request.getSession();
        //2.获取数据
        Object msg = session.getAttribute("msg");
        System.out.println(msg);

    }
}