思路：使用session的监听器
参拷：http://xace.iteye.com/blog/424250
监听器类
package com.chinacache.utils;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
import com.chinacache.entity.User;
public class OnLineUtil implements HttpSessionListener, HttpSessionAttributeListener, ServletContextListener {
private ServletContext application = null;
private Map<String, User> allUser = null;
@Override
/**
* session 创建时会调用这个方法
*/
public void sessionCreated(HttpSessionEvent se) {
allUser = (Map<String, User>) application.getAttribute("userMap");
String sessionId = se.getSession().getId();
if (allUser.get(sessionId) == null) {
allUser.put(sessionId, null);
}
}
@Override
/**
* 调用session.invalidate()时被调用
*/
public void sessionDestroyed(HttpSessionEvent se) {
String sessionId = se.getSession().getId();
if (allUser != null && allUser.get(sessionId) != null) {
allUser.remove(sessionId);
}
}
@Override
/**
* 应用启动时调用
*/
public void contextInitialized(ServletContextEvent sce) {
application = sce.getServletContext();
application.setAttribute("userMap", new HashMap<String, User>());
}
@Override
public void contextDestroyed(ServletContextEvent sce) {
// TODO Auto-generated method stub
}
@Override
/**
* session 中属性被增回时
*/
public void attributeAdded(HttpSessionBindingEvent se) {
String sessionId = se.getSession().getId();
if (allUser != null) {
User user = (User) se.getSession().getAttribute("currUser");
if (user.getUser_name() != null) {
allUser.put(sessionId, user);
}
}
}
@Override
public void attributeRemoved(HttpSessionBindingEvent se) {
// TODO Auto-generated method stub
}
@Override
/**
* session 中属性更改时
*/
public void attributeReplaced(HttpSessionBindingEvent se) {
HttpSession session = se.getSession();
String id = session.getId();
if (allUser != null) {
User user = (User) session.getAttribute("currUser");
if (user.getUser_name() != null) {
allUser.put(id, user);
}
}
}
}
web.xml
<listener> <listener-class>com.chinacache.utils.OnLineUtil</listener-class> </listener>
jsp展示（使用了ztree）
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<%@ page import="java.util.*"%>
<%@ page import="com.chinacache.entity.User"%>
<%@ taglib prefix="s" uri="http://www.springframework.org/tags/form"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet"
href="${projectPath}/resources/ztree/zTreeStyle/zTreeStyle.css"
type="text/css">
<script type="text/javascript"
src="${projectPath}/resources/ztree/jquery.ztree.core-3.5.min.js"></script>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Welcome to Starscream!</title>
</head>
<body>
<div class="container">
<div class="zTreeDemoBackground left">
<ul id="treeDemo" class="ztree"></ul>
</div>
</div>
</body>
<SCRIPT type="text/javascript">
var zNodes =<%
Map<String, User> l = (Map<String, User>)application.getAttribute("userMap");
Map<String,List<String>> users=new HashMap<String,List<String>>();
for(String id : l.keySet()){
String cgf=l.get(id).getCfg_value();
String username=l.get(id).getUser_name();
if(users.get(cgf)==null){
users.put(cgf, new ArrayList<String>());
}
users.get(cgf).add(username);
}
StringBuilder node= new StringBuilder("[{ name:'在线人员(").append(l.size()).append("人)'");
if(users.size()>0){
node.append(", open:true");
node.append(", children: [");
for(String cgf:users.keySet()){
List<String> usernames= users.get(cgf);
node.append(String.format("{ name:'%s(%s人)',",cgf,usernames.size()));
if(usernames.size()>0){
node.append("children: [");
for(String name:usernames){
node.append("{ name:'").append(name).append("'},");
}
node.deleteCharAt(node.length()-1);
}else{
node.append(", isParent:true");
}
node.append("]},");
}
node.deleteCharAt(node.length() - 1);
node.append("]");
} else {
node.append(", isParent:true");
}
node.append("}]");
out.println(node.toString());
%>;
var setting = { };
$(document).ready(function(){
$.fn.zTree.init($("#treeDemo"), setting, zNodes);
});
</SCRIPT>
</html>
LoginController.java
package com.chinacache.controller;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import org.apache.log4j.Logger;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.SessionAttributes;
import com.chinacache.entity.User;
@Controller
@SessionAttributes({ "currUser", "projectPath", "funcMap" })
public class LoginController {
private static Logger logger = Logger.getLogger(LoginController.class);
@RequestMapping("/")
public String showLoginPage(Model model) {
logger.info("showLoginPage is call!");
return "login";
}
@RequestMapping(value = "/user", method = RequestMethod.POST)
public String userLogin(@RequestParam(value = "user", required = false) User user, HttpServletRequest request, Model model) {
model.addAttribute("currUser", user);
return "forward:/home";
}
@RequestMapping(value = "/logout")
public String LogOut(HttpServletRequest request,Model model){
HttpSession session = request.getSession();
if(session!=null){
model.addAttribute("currUser",new User());
session.removeAttribute("currUser");
session.invalidate();
}
return "login";
}
}
由于使用@SessionAttributes把model里的属性赋值给session中，在调用LogOut后跳到login页（此时model里还存放着user信息，会自动赋给新session），所以把model里的值User赋值空user，在判断当前session中的user中的属性（如username）是否为null，如果为null表示还没有登入即不会放到在线列表中
转的：http://xace.iteye.com/blog/424250
javax.servlet.http.HttpSession 这个类是很常用的，每当我们浏览网站，不论有没有登陆，都会产生1个session，它记录了和浏览者相关的数据；
下面介绍session的2个监听器接口：
1）javax.servlet.http.HttpSessionBindingListener;
实现这个接口的类，每当被存放到session或从session中移除都会出发接口中相应的方法，从而实现监听的效果；
2）javax.servlet.http.HttpSessionListener;
实现这个接口的类，本身就是1个监听器，每当有session生成或消亡时，都触发接口中相应的方法，从而实现监听器的效果；
HttpSessionListener 的实现类本身就是一个监听器，要使用它需要在 web.xml 中启动这个监听器，例如
Xml代码
- <listener>
- <listener-class>packname.classname</listener-class>
- </listener>
3）这2个监听器是有区别的
前者的触发取决于 session 中加入的属性；
后者的触发取决于 session 本身的产生和消亡；
与shangshu 之类似的还有
对ServletContext的监听和对Request监听
应用：当前在线人数列表
在线人数列表是对所有人起作用，数据应放到application中。即ServletContext对象
OnLineDemo.java
Java代码
- package demo;
- import java.util.ArrayList;
- import java.util.List;
- import javax.servlet.ServletContext;
- import javax.servlet.ServletContextEvent;
- import javax.servlet.ServletContextListener;
- import javax.servlet.http.HttpSessionAttributeListener;
- import javax.servlet.http.HttpSessionBindingEvent;
- import javax.servlet.http.HttpSessionEvent;
- import javax.servlet.http.HttpSessionListener;
- /*
- * <listener> <listener-class>demo.OnLineDemo</listener-class>
- * </listener>
- */
- public class OnlineDemo implements ServletContextListener, HttpSessionListener,
- HttpSessionAttributeListener {
- // 声明一个ServletContext对象
- private ServletContext application = null;
- public void contextInitialized(ServletContextEvent sce) {
- // 容器初始化时，向application中存放一个空的容器
- this.application = sce.getServletContext();
- this.application.setAttribute("alluser", new ArrayList());
- }
- public void contextDestroyed(ServletContextEvent sce) {
- }
- public void sessionCreated(HttpSessionEvent se) {
- }
- public void sessionDestroyed(HttpSessionEvent se) {
- // 将用户名称从列表中删除
- List l = (List) this.application.getAttribute("alluser");
- String value = (String) se.getSession().getAttribute("uname");
- l.remove(value);
- this.application.setAttribute("alluser", l);
- }
- public void attributeAdded(HttpSessionBindingEvent se) {
- // 如果登陆成功，则将用户名保存在列表之中
- List l = (List) this.application.getAttribute("alluser");
- l.add(se.getValue());
- this.application.setAttribute("alluser", l);
- }
- public void attributeRemoved(HttpSessionBindingEvent se) {
- }
- public void attributeReplaced(HttpSessionBindingEvent se) {
- }
- }
online.jsp
Html代码
- <%@ page contentType="text/html;charset=gb2312"%>
- <%@ page import="java.util.*"%>
- <form action="online.jsp" method="post">
- 用户名：
- <input type="text" name="name">
- <input type="submit" value="登陆">
- <a href="logout.jsp">注销</a>
- </form>
- <!-- 向session接收输入的用户名 -->
- <%
- if(request.getParameter("name")!=null)
- session.setAttribute("uname",request.getParameter("name")) ;
- %>
- <h2>在线人员</h2>
- <hr>
- <%
- List l = (List)application.getAttribute("allUser");
- for(Object o : l)
- out.println(o);
- %>
logout.jsp
Html代码
- <%
- session.invalidate() ;
- %>