利用监听器实现网站在线人数统计

来源：互联网发布：软件提速精灵编辑：程序博客网时间：2024/05/05 22:27

ServletContextListenerImpl.java代码

public class ServletContextListenerImpl implements ServletContextListener {
public void contextDestroyed(ServletContextEvent event) {
ServletContext application = event.getServletContext();
application.removeAttribute("onLineNum");
}
public void contextInitialized(ServletContextEvent event) {
//利用servletContextEvent对象创建servletContext
int num = 0;
ServletContext application = event.getServletContext();
application.setAttribute("onLineNum", num);//初始默认在线人数为0
}
}

HttpSessionListnerImpl.java代码

public class HttpSessionListnerImpl implements HttpSessionListener {

public void sessionCreated(HttpSessionEvent event) {
//通过event获得servletContext对象
ServletContext application = event.getSession().getServletContext();
//拿到servletContext空间中储存的onLineNum
Integer num = (Integer)application.getAttribute("onLineNum");
if(num != null){
//如果存在，则将拿到的数量加一并到重新放入到servletContext空间中
num = num + 1;
application.setAttribute("onLineNum", num);
} else {
//如果不存在，则设置onLineNum为1
application.setAttribute("onLineNum", 1);
}
}

public void sessionDestroyed(HttpSessionEvent event) {
System.out.println("一个session关闭了");
//通过event获得servletContext对象
ServletContext application = event.getSession().getServletContext();
//拿到servletContext空间中储存的onLineNum
Integer num = (Integer)application.getAttribute("onLineNum");
num = num - 1;
//将拿到的数量减一并到重新放入到servletContext空间中
application.setAttribute("onLineNum", num);
}
}

对应的在web.xml文件中进行监听器配置

<listener>
<listener-class>
com.hk.listener.ServletContextListenerImpl
</listener-class>
</listener>

<listener>
<listener-class>
com.hk.listener.HttpSessionListnerImpl
</listener-class>
</listener>

jsp代码

<body>
当前在线人数：${onLineNum }

</body>

测试结果

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