web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
<display-name>servlet</display-name>
<servlet>
<description></description>
<display-name>Session</display-name>
<servlet-name>Session</servlet-name>
<servlet-class>com.xiangshuai.SessionDemo</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Session</servlet-name>
<url-pattern>/session</url-pattern>
</servlet-mapping>
</web-app>
SessionDemo.java
package com.xiangshuai;
import java.io.IOException;
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 javax.servlet.http.HttpSession;
/**
* @author xiangshuai
* cookie,session自我理解
*/
public class SessionDemo extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public SessionDemo() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession session = request.getSession();
Cookie[] cookies = request.getCookies();
if(cookies==null){//第一次请求
session.setAttribute("username", "lisi");
Cookie cookie = new Cookie("JSESSIONID", session.getId());
/*JSESSIONID的这个cookie的值是此session 的id,cookie的生命周期 1.如果设置了cookie.setMaxAge,那么在一次请求完成,即一次请求响应到浏览器后开始算
* 到setMaxAge这个时间止(那么和浏览器关不关闭已经没关系,因为此COOKIE的相关信息已存到磁盘,而非浏览器缓存),2.如果没有设置持久化到硬盘即没有cookie.setMaxAge,那么生命周期就是浏览器关掉即此cookie消亡*/
cookie.setMaxAge(2*60);
/* 将此cookie持久化到客户端,设置此cookie的生命周期为2分钟,即使客户端关闭
* 下次用此浏览器发起请求在cookie的生命周期2分钟以内,会继续从客户端磁盘中找到这个cookie的信息,
* tomcat容器会继续封装到request中在请求头中带这个cookie发起请求,当request获得session时request.getSession(),通过这个
* JSESSIONID 得到这个cookie的value,通过这个value在tomcat容器中(Map<String JSESSIONIDcookieValue,Session session>)找到对应的session
* 如果session还未销毁,默认是30分钟(从浏览器最后一次回话完成开始算到设置销毁时间--默认是30分钟)
* */
response.addCookie(cookie);
/* 添加到response缓存域中,由tomcat解析response缓存域响应到浏览端,只有响应到浏览端,浏览器才能做出反应,将setMaxAge
的cookie持久化到磁盘,没有setMaxAge的cookie只会保持到浏览器,浏览器一关cookie就找不到了
*
* */
}
Object username = session.getAttribute("username");
System.out.println(session.toString());
response.getWriter().append(username+"").append(session.getId());
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}