web程序统计在线人数的实现方式！

只需要实现session监听器，然后再根据具体逻辑进行操作:

//统计当前在线用户个数public class UserCountListener implements HttpSessionListener {public void sessionCreated(HttpSessionEvent se) {ServletContext context = se.getSession().getServletContext();Integer num = (Integer) context.getAttribute("num");if(num==null){context.setAttribute("num", 1);}else{num++;context.setAttribute("num", num);}}public void sessionDestroyed(HttpSessionEvent se) {ServletContext context = se.getSession().getServletContext();Integer num = (Integer) context.getAttribute("num");if(num==null){context.setAttribute("num", 1);}else{num--;context.setAttribute("num", num);}}}