监听器学习-统计网站在线人数

我不是女神ヾ 2022-03-29 12:54 260阅读 0赞

>     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}