HttpSessionListener,ServletContextListener, ServletContextAttributeListener,ServletContainer监听在线人数

最新推荐文章于 2021-03-23 13:11:35 发布

杨过悔

最新推荐文章于 2021-03-23 13:11:35 发布

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分类专栏： Jsp编程笔记

本文链接：https://blog.youkuaiyun.com/u013571243/article/details/42321367

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本文介绍了一个用于统计在线人数的监听器实现，该监听器通过实现HttpSessionListener接口来监听session创建和销毁事件，从而更新在线人数计数，并将当前在线人数作为属性存储在ServletContext中。

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配置文件

	<listener>
		<listener-class>com.SessionCount</listener-class>
	</listener>

实现HttpSessionListener接口监听sesson事件

package com;

import java.util.Set;

import javax.servlet.ServletContainerInitializer;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextAttributeEvent;
import javax.servlet.ServletContextAttributeListener;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.ServletException;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class SessionCount implements HttpSessionListener,
		ServletContextListener, ServletContextAttributeListener,
		ServletContainerInitializer {
	private int count;
	private ServletContext context = null;

	public SessionCount() {
		count = 0;

	}

	public void setContext(HttpSessionEvent event) {
		event.getSession().getServletContext()
				.setAttribute("onLine", new Integer(count));
	}

	@Override
	public void onStartup(Set<Class<?>> arg0, ServletContext arg1)
			throws ServletException {

 	}

	@Override
	public void attributeAdded(ServletContextAttributeEvent arg0) {
		PrintLog("attributeAdded/" + arg0.getName() + "-" + arg0.getValue());

	}

	@Override
	public void attributeRemoved(ServletContextAttributeEvent arg0) {
		PrintLog("attributeRemoved/" + arg0.getName() + "-" + arg0.getValue());

	}

	@Override
	public void attributeReplaced(ServletContextAttributeEvent arg0) {
		PrintLog("attributeReplaced/" + arg0.getName() + "-" + arg0.getValue());

	}

	@Override
	public void contextDestroyed(ServletContextEvent arg0) {
		this.context = null;

	}

	@Override
	public void contextInitialized(ServletContextEvent arg0) {
		this.context = arg0.getServletContext();

	}

	@Override
	public void sessionCreated(HttpSessionEvent event) {
		count++;
		setContext(event);
		PrintLog("onLine_:" + count);
	}

	@Override
	public void sessionDestroyed(HttpSessionEvent event) {
		count--;
		setContext(event);
		PrintLog("onLine_:" + count);
	}

	private void PrintLog(String log) {
		System.out.println("log:" + log);
	}
}