用HttpSessionListener统计在线用户或做账号在线人数管理

public class MySessionListener implements HttpSessionListener{

    /**
     * <p>Title: sessionCreated</p> 
     * <p>Description: </p> 
     * @param se 
     * @see javax.servlet.http.HttpSessionListener#sessionCreated(javax.servlet.http.HttpSessionEvent) 
     */
    @Override
    public void sessionCreated(HttpSessionEvent se) {
        int i = 0;
    }

    /**
     * <p>Title: sessionDestroyed</p> 
     * <p>Description: </p> 
     * @param se 
     * @see javax.servlet.http.HttpSessionListener#sessionDestroyed(javax.servlet.http.HttpSessionEvent) 
     */
    @Override
    public void sessionDestroyed(HttpSessionEvent se) {
         User userInfo = (User)se.getSession().getAttribute(Constants.SESSION_USER_INFO);
         if(null != userInfo){
             //该账户的在线人数减一
             UserService userService = (UserService) SpringContextUtil.getBean("userService");
             userService.UpdateOnlineNum(userInfo.getLoginName(), -1);
         }
         else{
             
         }
    }

}