1、ServletContext记录个数

package cn.demo.listener;import javax.servlet.ServletContext;import javax.servlet.ServletContextEvent;import javax.servlet.ServletContextListener;public class MyServletContextListener implements ServletContextListener {	@Override	public void contextInitialized(ServletContextEvent sce) {		// 容器一启动ServletContext对象就会创建，该方法就会执行		System.out.println("容器创建了...");		ServletContext servletContext = sce.getServletContext();		int count = 0;		servletContext.setAttribute("count", count);	}	@Override	public void contextDestroyed(ServletContextEvent sce) {		// 容器销毁ServletContext对象就销毁，该方法就会执行		System.out.println("容器销毁了...");	}}web.xml配置   
      	
     
      cn.demo.listener.MyServletContextListener
       
    

2、监听session创建

package cn.demo.listener;import java.util.Date;import javax.servlet.ServletContext;import javax.servlet.http.HttpSessionEvent;import javax.servlet.http.HttpSessionListener;/** * 监听session个数 *  */public class MySessionListener implements HttpSessionListener {	@Override	public void sessionCreated(HttpSessionEvent se) {		// 当服务器创建一个session的时候该方法执行		System.out.println("session被创建了..." + se.getSession().getId() + "..." + new Date());		ServletContext servletContext = se.getSession().getServletContext();		int count = (Integer) servletContext.getAttribute("count");		count++;		servletContext.setAttribute("count", count);	}	@Override	public void sessionDestroyed(HttpSessionEvent se) {		System.out.println("session被销毁了..." + se.getSession().getId() + "..." + new Date());		ServletContext servletContext = se.getSession().getServletContext();		int count = (Integer) servletContext.getAttribute("count");		count--;		servletContext.setAttribute("count", count);	}}web.xml  
      	
     
      cn.itcast.listener.MySessionListener
       
    

3、页面显示

showSessionCount.jsp显示

	
当前服务器session个数：${applicationScope.count}