监听器统计在线人数

 

 

package com.zyb.listener;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;


public class MyListener
  implements HttpSessionListener, ServletContextListener
{
  //session对象创建表示用户登录
  public void sessionCreated(HttpSessionEvent se) {
    ServletContext sc = se.getSession().getServletContext();
    
    int count = ((Integer)sc.getAttribute("count")).intValue();
    
    sc.setAttribute("count", Integer.valueOf(++count));
  }



  //session对象销毁表示用户推出登录
  public void sessionDestroyed(HttpSessionEvent se) {
    ServletContext sc = se.getSession().getServletContext();
    
    int count = ((Integer)sc.getAttribute("count")).intValue();
    
    sc.setAttribute("count", Integer.valueOf(--count));
  }



  //创建application对象（服务器一启动就会运行）
  public void contextInitialized(ServletContextEvent sce) {
    ServletContext sc = sce.getServletContext();
    
    sc.setAttribute("count", Integer.valueOf(0));
  }
  
  public void contextDestroyed(ServletContextEvent sce) {}
}