jsp簡單實現統計在線人數

通過重寫HttpSessionListener接口實現

//session操作類
public class SessionMap {


 private static Map<String,HttpSession> sesMap = new HashMap<String,HttpSession>();

 private static final Object flag = new Object();

 private SessionMap(){

 }

 private static class MapUtilsN{
     private static SessionMap sessionMap = new SessionMap();
 }

 public static SessionMap getInstance(){
     return MapUtilsN.sessionMap;
 }

 public void addMap(String sessionId,HttpSession session){
     synchronized (flag) {
         if(!sesMap.containsKey(sessionId)){
             sesMap.put(sessionId, session);
         }
     }
 }

 public void removeMap(String sessionId){
     synchronized (flag) {
         sesMap.remove(sessionId);
     }
 }

 public int getSize(){
     synchronized (flag) {
         return sesMap.size();
     }
 }

 public HttpSession getSession(String key){
     synchronized (flag) {
         return sesMap.get(key);
     }
  }

}
//監聽session創建及銷毀
public class MySessionListner implements HttpSessionListener{
public void sessionCreated(HttpSessionEvent arg0) {
     SessionMap.getInstance().addMap(arg0.getSession().getId(), arg0.getSession());
 }
public void sessionDestroyed(HttpSessionEvent arg0) {
     SessionMap.getInstance().removeMap(arg0.getSession().getId());
 }
}
 </pre> 


//web.xml中配置監聽器
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
 xmlns="http://java.sun.com/xml/ns/javaee" 
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
 http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  <!-- 配置監聽器 -->
  <listener>  
      <listener-class>  
        practice.listner.MySessionListner  
      </listener-class>  
  </listener>
   <!-- 設置session超時時間 -->
  <session-config>
   <session-timeout>10</session-timeout>
  </session-config>
</web-app>