使用SessionListener统计在线人数

1.编辑监听类:

import  javax.servlet.http.HttpSessionListener;
import  javax.servlet.http.HttpSessionEvent;
import  org.apache.log4j.Logger;

/** */ /**
 * Session监听器
 */

public   class  SessionListener  implements  HttpSessionListener  ... {
  private Logger logger=Logger.getLogger(this.getClass());

  private long count=0;
  public synchronized void sessionCreated(HttpSessionEvent se) ...{
    this.count=this.count+1;
    se.getSession().getServletContext().setAttribute("count",this.count+"");
  }
  public synchronized void sessionDestroyed(HttpSessionEvent se) ...{
    this.count=this.count-1;
    se.getSession().getServletContext().setAttribute("count",this.count+"");
  }
}

 

 2.注册监听到web.xml:

< web - app >
...
   < listener >
     < listener - class > com.link2friend.friend.sessionlistener.SessionListener </ listener - class >
   </ listener >
...
</ web - app >

 

3.网页上使用:

<%=application.getAttribute("count")%>