目录
目录
概念
- 实现特定接口的普通java类
*监听特定对象的创建、销毁或属性变化：-
对象自己创建自己用：无需监听
-
对象别人创建自己用：需要监听
-
Servlet中需要监听的对象：
-
Request--->request监听器
-
session--->session相关监听器
-
servletContext---->servletContext监听器
-
-
监听器功能
监听创建或销毁
- Interface ServletRequestListener 监听request对象的创建或销毁
- Interface HttpSessionListener 监听session对象的创建或销毁
- Interface ServletContextListener 监听servletContext对象的创建或销毁
Demo:
package per.liyue.code.listener;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
public class ServletRequestListenerDemo implements ServletRequestListener {
@Override
public void requestDestroyed(ServletRequestEvent sre) {
//获取值
Object obj = sre.getServletRequest().getAttribute("testName");
System.out.println("获取到的属性值为：" + obj);
System.out.println("销毁对象时候操作...");
}
@Override
public void requestInitialized(ServletRequestEvent sre) {
System.out.println("创建对象时候操作...");
}
}
<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
This is my JSP page. <br>
<%request.setAttribute("testName", "testvalue"); %>
</body>
</html>
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>WebDemo2</display-name>
<listener>
<listener-class>per.liyue.code.listener.ServletRequestListenerDemo</listener-class>
</listener>
</web-app>
监听属性变化
-
Interface ServletRequestAttributeListener 监听request对象属性变化: 添加、移除、修改
-
Interface HttpSessionAttributeListener 监听session对象属性变化: 添加、移除、修改
-
Interface ServletContextAttributeListener 监听servletContext对象属性变化
session相关监听
- Interface HttpSessionBindingListener 监听对象绑定到session上的事件
- Interface HttpSessionActivationListener(了解) 监听session序列化及反序列化的事件