Servlet---Listener

package com.an.tomcatservlet;

import javax.servlet.ServletContextAttributeEvent;
import javax.servlet.ServletContextAttributeListener;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.ServletRequest;
import javax.servlet.ServletRequestAttributeEvent;
import javax.servlet.ServletRequestAttributeListener;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
import javax.servlet.http.HttpSessionActivationListener;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionBindingListener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

/**
 * @author apy
 * @description
 * @date 2021/10/21 17:29
 */
public class MyListener implements ServletRequestListener
        ,ServletRequestAttributeListener
        ,ServletContextListener
        ,ServletContextAttributeListener
        ,HttpSessionListener
        ,HttpSessionBindingListener
        ,HttpSessionActivationListener
        ,HttpSessionAttributeListener{

    public void requestInitialized(ServletRequestEvent sre) {
        ServletRequest servletRequest = sre.getServletRequest();
        // do something...
    }

    public void requestDestroyed(ServletRequestEvent sre) {

    }

    public void attributeAdded(ServletRequestAttributeEvent srae) {

    }

    public void attributeRemoved(ServletRequestAttributeEvent srae) {

    }

    public void attributeReplaced(ServletRequestAttributeEvent srae) {

    }

    public void contextInitialized(ServletContextEvent sce) {

    }

    public void contextDestroyed(ServletContextEvent sce) {

    }

    public void attributeAdded(ServletContextAttributeEvent event) {

    }

    public void attributeRemoved(ServletContextAttributeEvent event) {

    }

    public void attributeReplaced(ServletContextAttributeEvent event) {

    }

    public void sessionCreated(HttpSessionEvent se) {

    }

    public void sessionDestroyed(HttpSessionEvent se) {

    }

    public void valueBound(HttpSessionBindingEvent event) {

    }

    public void valueUnbound(HttpSessionBindingEvent event) {

    }

    /**
     * 【servlet Listener】
     *      why？
     *          解决 共享对象 内容发生变化 时， 在发生前、发生后 做处理；
     *
     *          Servlet2.3 提供了 对 ServletContext、HttpSession对象的变化的 监听器；
     *          Servlet2.4 增加了 对 ServletRequest对象的变化的 监听器；
     *
     *      what？
     *          ServletContext监听器：监听 ServletContext对象，可以 使 web应用 得知 web组件的 加载、卸载情况等；
     *              ServletContextListener
     *              ServletContextAttributeListener
     *
     *              ServletContextEvent
     *              ServletContextAttributeEvent
     *
     *          HttpSession监听器：监听 HttpSession对象变化，可以 使 web应用 了解 会话期间的状态 并 做出响应；
     *              HttpSessionListener
     *              HttpSessionActivationListener  实现数据 内存->磁盘，磁盘->内存；
     *
     *              HttpSessionEvent
     *
     *
     *              HttpSessionAttributeListener
     *              HttpSessionBindingListener
     *
     *              HttpSessionBindingEvent
     *
     *
     *          ServletRequest监听器：监听 ServletRequest对象变化，可以 使 web应用 控制web请求的生命周期；
     *              ServletRequestListener
     *              ServletRequestAttributeListener
     *
     *              ServletRequestEvent
     *              ServletRequestAttributeEvent
     *
     *      How？
     *          创建普通Java类，实现 对应的Listener,重写相应的方法；
     *          在web.xml中配置相应的 Listener；
     */
}