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public class UserSessionListener implements HttpSessionListener {
@SuppressWarnings("rawtypes")
@Override
public void sessionCreated(HttpSessionEvent event) {
// TODO Auto-generated method stub
HttpSession session = event.getSession();
ServletContext application = session.getServletContext();
// 在application范围由一个HashSet集保存所有的session
HashSet sessions = (HashSet) application.getAttribute("sessions");
if (sessions == null) {
sessions = new HashSet();
application.setAttribute("sessions", sessions);
}
// 新创建的session均添加到HashSet集中
sessions.add(session);
// 可以在别处从application范围中取出sessions集合
// 然后使用sessions.size()获取当前活动的session数,即为“在线人数”
System.out.println("session-------"+sessions.size());
}
@SuppressWarnings("rawtypes")
@Override
public void sessionDestroyed(HttpSessionEvent event) {
// TODO Auto-generated method stub
HttpSession session = event.getSession();
ServletContext application = session.getServletContext();
HashSet sessions = (HashSet) application.getAttribute("sessions");
synchronized (this) {
// 销毁的session均从HashSet集中移除
sessions.remove(session);
}
System.out.println("session remove-------"+sessions.size());
}
}
<!-- online user -->
<listener>
<listener-class>*.UserSessionListener</listener-class>
</listener>