监听器学习-统计网站在线人数-蒲公英云

监听器学习-统计网站在线人数

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创建时
    @Override
    public void sessionCreated(HttpSessionEvent se) {
        //  获取ServletContext 对象
        ServletContext ser2 =  se.getSession().getServletContext();
        //  获取在线人数统计变量
        int count = (int)ser2.getAttribute("count");
        ser2.setAttribute("count",++count);
    }
    //session销毁时
    @Override
    public void sessionDestroyed(HttpSessionEvent se) {
        //  获取ServletContext 对象
        ServletContext ser2 =  se.getSession().getServletContext();
        //  获取在线人数统计变量
        int count = (int)ser2.getAttribute("count");
        ser2.setAttribute("count",--count);
    }
    //  application 对象初始化
    @Override
    public void contextInitialized(ServletContextEvent ser) {
        //  获取application
        ServletContext ser2 = ser.getServletContext();
        // 在application对象存储变量统计在线人数
        ser2.setAttribute("count",0);
    }
    @Override
    public void contextDestroyed(ServletContextEvent servletContextEvent) {
    }
}
web.xml 配置监听器
<listener>
   <listener-class>com.suicai.listener.MyListener</listener-class>
</listener>
jsp 取值
${applicationScope.count}