Java Web监听器Listener接口是什么

// 用于监听session创建和销毁的监听器
package listener;

import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class SessionListener implements HttpSessionListener {
  @Override
  public void sessionCreated(HttpSessionEvent httpSessionEvent) {
    // 获取本次事件创建session的id
    String sessionId = httpSessionEvent.getSession().getId();
    System.out.println("create session that id = " + sessionId);
  }

  @Override
  public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {
    // 删除session的id
    String sessionId = httpSessionEvent.getSession().getId();
    System.out.println("session has been destroy that id = " + sessionId);
  }
}

<&#63;xml version="1.0" encoding="UTF-8"&#63;>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns="http://xmlns.jcp.org/xml/ns/javaee"
     xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
     id="WebApp_ID" version="3.1">
 <display-name>Archetype Created Web Application</display-name>
 <welcome-file-list>
  <welcome-file>index.jsp</welcome-file>
 </welcome-file-list>

 <listener>
 	<!-- 在listener包下的SessionListener类 -->
  <listener-class>listener.SessionListener</listener-class>
 </listener>

</web-app>