servlet中的监听器深入

首先，什么是监听器？

监听器主要有以下几种：

现在，我们来一一试过，把所有的事件监听器全部写好，按照输出，我们来分析：

首先是：ServletContextEvent事件：

package com.xust.jia.listener;import java.text.SimpleDateFormat;import java.util.Date;import javax.servlet.ServletContextEvent;import javax.servlet.ServletContextListener;public class Listenerapplication implements ServletContextListener{@Overridepublic void contextDestroyed(ServletContextEvent arg0) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date())+"application结束");System.out.println();System.out.println();}@Overridepublic void contextInitialized(ServletContextEvent arg0) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date())+"application开始");System.out.println();System.out.println();}}

接下来是

ServletContextAttributeEvent:

package com.xust.jia.listener;import java.text.SimpleDateFormat;import java.util.Date;import javax.servlet.ServletContextAttributeEvent;import javax.servlet.ServletContextAttributeListener;public class Listernerapplicationattr implements ServletContextAttributeListener{@Overridepublic void attributeAdded(ServletContextAttributeEvent arg0) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date())+"application的属性被新建"+arg0.getName());System.out.println();System.out.println();}@Overridepublic void attributeRemoved(ServletContextAttributeEvent arg0) {// TODO Auto-generated method stubSimpleDateFormat sdFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdFormat.format(new Date())+"application的"+arg0.getName()+"属性被删除");System.out.println();System.out.println();}@Overridepublic void attributeReplaced(ServletContextAttributeEvent arg0) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date())+"application的"+arg0.getName()+"属性值被修改为:"+arg0.getValue());System.out.println();System.out.println();}}

HttpSessionEvent事件的HttpSessionListener接口：

package com.xust.jia.listener;import java.text.SimpleDateFormat;import java.util.Date;import javax.servlet.http.HttpSessionEvent;import javax.servlet.http.HttpSessionListener;public class Listenersession implements HttpSessionListener{@Overridepublic void sessionCreated(HttpSessionEvent se) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date()) + "session对象被创建" + se.getSession());System.out.println();System.out.println();}@Overridepublic void sessionDestroyed(HttpSessionEvent se) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date())+"session对象被销毁" + se.getSource()+se.getClass());System.out.println();System.out.println();}}

HttpSessionEvent事件的HttpSessionActivationListener接口：

这个接口并不是直接监听的，而是依附于具体的实体类对象中，即由具体需要的实体类进行实现这个接口，实现这个接口所定义的方法，这样，当在使用到这个实体类的对象时，就会触发这个监听器，从而执行对应的方法：

首先，我们现在实体类中实现这个接口：

package com.xust.jia.listener;import java.text.SimpleDateFormat;import java.util.Date;import javax.servlet.http.HttpSessionActivationListener;import javax.servlet.http.HttpSessionEvent;public class Man implements HttpSessionActivationListener{@Overridepublic void sessionDidActivate(HttpSessionEvent se) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date()) +"这是session的didActive方法");System.out.println();System.out.println();}@Overridepublic void sessionWillPassivate(HttpSessionEvent se) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date())+"这是session的Willpassivate方法");System.out.println();System.out.println();}public Man() {super();// TODO Auto-generated constructor stub}}

接下来，我们重写一个测试页面：

<%@page import="java.text.SimpleDateFormat"%><%@page import="com.xust.jia.listener.Man"%><%@page import="java.util.Date" %><%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%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>这是测试session的activationListener接口</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>    <h1>测试session的activationListener接口</h1>    <%    if(session.getAttribute("act") == null)    {    Man man = new Man();    session.setAttribute("act", man);    }    System.out.println(session.getId()+session.getAttribute("act"));    Date d = new Date(session.getCreationTime());    System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(d));     %>  </body></html>

然后，在对服务器进行配置：

其中，htmlday1是项目名称，然后，在里面写入：

接下来，我们先打开配置的xml,然后通过xml来访问测试页面进行测试：

说明这个测试页面里的语句被执行，然后关闭服务器，重新打开服务器,发现在E:盘下多了一个文件夹，a:

发现多了一个SESSION文件，打开如下：

在控制台输出以下信息：

注意，关闭服务器是正常关闭，不是直接关闭。

HttpSessionBindingEvent事件的HttpSessionAttributeListener接口：

package com.xust.jia.listener;import java.text.SimpleDateFormat;import java.util.Date;import javax.servlet.http.HttpSessionAttributeListener;import javax.servlet.http.HttpSessionBindingEvent;public class Listenersessionattr implements HttpSessionAttributeListener{@Overridepublic void attributeAdded(HttpSessionBindingEvent event) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date())+"session的"+event.getName()+"属性被增加,值为:"+event.getValue());System.out.println();System.out.println();}@Overridepublic void attributeRemoved(HttpSessionBindingEvent event) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date())+"session的"+event.getName()+"属性被删除，值为:"+event.getValue());System.out.println();System.out.println();}@Overridepublic void attributeReplaced(HttpSessionBindingEvent event) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date())+"session的"+event.getName()+"属性值被修改为:"+event.getValue());System.out.println();System.out.println();}}

HttpSessionBindingEvent事件的HttpSessionBindingListener接口：

因为这个接口比较特殊，是在实体类中进行实现方法，而且不需要在Web.xml文件中进行配置，所以，我们只是简单的检测验证一下这个接口：

package com.xust.jia.listener;import java.text.SimpleDateFormat;import java.util.Date;import javax.servlet.http.HttpSessionBindingEvent;import javax.servlet.http.HttpSessionBindingListener;public class Person implements HttpSessionBindingListener{@Overridepublic void valueBound(HttpSessionBindingEvent event) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date())+"这是Binding的Bound"+event.getName()+event.getValue());System.out.println();System.out.println();}@Overridepublic void valueUnbound(HttpSessionBindingEvent event) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date())+"这是Binding的Unbound"+event.getName()+event.getValue());System.out.println();System.out.println();}public Person() {super();// TODO Auto-generated constructor stub}}

接下来，我们在servlet类中进行调用这个类，然后把这个类对象加载到会话的属性中，最后使用session的方法，销毁这个session：

在servlet的post或者get方法中写入如下代码：

Person person = new Person();HttpSession hsHttpSession = request.getSession();hsHttpSession.setAttribute("person", person);hsHttpSession.invalidate();

接下来，我们调入这个servlet方法中，进行测试：

显示结果如下：

ServletRequestEvent事件：

package com.xust.jia.listener;import java.text.SimpleDateFormat;import java.util.Date;import javax.servlet.ServletRequestEvent;import javax.servlet.ServletRequestListener;public class Listenerrequest implements ServletRequestListener{@Overridepublic void requestDestroyed(ServletRequestEvent arg0) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date())+"request被创建");System.out.println();System.out.println();}@Overridepublic void requestInitialized(ServletRequestEvent arg0) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date())+"request被销毁");System.out.println();System.out.println();}}

ServletRequestAttributeEvent事件：

package com.xust.jia.listener;import java.text.SimpleDateFormat;import java.util.Date;import javax.servlet.ServletRequestAttributeEvent;import javax.servlet.ServletRequestAttributeListener;public class Listenerrequestattr implements ServletRequestAttributeListener{@Overridepublic void attributeAdded(ServletRequestAttributeEvent arg0) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date())+"request的"+arg0.getName()+"属性被创建，值为:"+arg0.getValue());System.out.println();System.out.println();}@Overridepublic void attributeRemoved(ServletRequestAttributeEvent arg0) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date())+"request的"+arg0.getName()+"属性被删除，值为:"+arg0.getValue());System.out.println();System.out.println();}@Overridepublic void attributeReplaced(ServletRequestAttributeEvent arg0) {// TODO Auto-generated method stubSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println();System.out.println();System.out.println(sdf.format(new Date())+"request的"+arg0.getName()+"属性被修改，值为:"+arg0.getValue());System.out.println();System.out.println();}}

接下来，我们写一个测试页面：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%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>secondjsp 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="../CSS/index.css"><script type="text/javascript" src="./js/jquery.js"></script><script type="text/javascript">$(document).ready(function() {$("#div").hide();$("#button").click(function() {$("#div").show();});});</script></head><body><%String nameString = "小李子";String pswdString = "1234567";String sexString = "男";String ageString = "21";/* String nmString = request.getParameter("user");String pdString = request.getParameter("pswd");String sString = request.getParameter("sex");String aString = request.getParameter("age"); *//* nameString = new String(nmString.getBytes("ISO-8859-1"), "UTF-8");pswdString = new String(pdString.getBytes("ISO-8859-1"), "UTF-8");sexString = new String(sString.getBytes("ISO-8859-1"), "UTF-8");ageString = new String(aString.getBytes("ISO-8859-1"), "UTF-8"); */session.setAttribute("name", nameString);session.setAttribute("pswd", pswdString);session.setAttribute("sex", sexString);session.setAttribute("age", ageString);request.setAttribute("name", nameString);request.setAttribute("pswd", pswdString);request.setAttribute("sex", sexString);request.setAttribute("age", ageString);pageContext.setAttribute("name", nameString);pageContext.setAttribute("pswd", pswdString);pageContext.setAttribute("sex", sexString);pageContext.setAttribute("age", ageString);application.setAttribute("name", nameString);application.setAttribute("pswd", pswdString);application.setAttribute("sex", sexString);application.setAttribute("age", ageString);application.setAttribute("name", "123");application.setAttribute("pswd", "456");application.setAttribute("sex", "女");application.setAttribute("age", "25");request.setAttribute("name", "123");request.setAttribute("pswd", "456");request.setAttribute("sex", "女");request.setAttribute("age", "25");session.setAttribute("name", "123");session.setAttribute("pswd", "456");session.setAttribute("sex", "女");session.setAttribute("age", "25");String namepageContextString = (String) pageContext.getAttribute("name");String namesessionString = (String) session.getAttribute("name");String namerequestString = (String) request.getAttribute("name");String nameapplicationString = (String) application.getAttribute("name");String pswdpageContextString = (String) pageContext.getAttribute("pswd");String pswdsessionString = (String) session.getAttribute("pswd");String pswdrequestString = (String) request.getAttribute("pswd");String pswdapplicationString = (String) application.getAttribute("pswd");String sexpageContextString = (String) pageContext.getAttribute("sex");String sexsessionString = (String) session.getAttribute("sex");String sexrequestString = (String) request.getAttribute("sex");String sexapplicationString = (String) application.getAttribute("sex");String agepageContextString = (String) pageContext.getAttribute("age");String agesessionString = (String) session.getAttribute("age");String agerequestString = (String) request.getAttribute("age");String ageapplicationString = (String) application.getAttribute("age");%><div align="center"><button id="button">点击进行pageContext测试</button><br> <a href="JSP/four.jsp">点击进行session测试</a><br> <b>进行application测试:重启浏览器，并转到此链接：http://localhost:8080/htmlday1/JSP/four.jsp</b></div><div align="center" id="div"style="font-family: 楷体;font-size: 25px;color: green;">客户信息：<br> pageContext:<br> 姓名：<%=namepageContextString%><br>密码：<%=pswdpageContextString%><br> 性别：<%=sexpageContextString%><br>年龄：<%=agepageContextString%><br> session:<br> 姓名：<%=namesessionString%><br>密码：<%=pswdsessionString%><br> 性别：<%=sexsessionString%><br>年龄：<%=agesessionString%><br> request:<br> 姓名：<%=namerequestString%><br>密码：<%=pswdrequestString%><br> 性别：<%=sexrequestString%><br>年龄：<%=agerequestString%><br> application:<br> 姓名：<%=nameapplicationString%><br>密码：<%=pswdapplicationString%><br> 性别：<%=sexapplicationString%><br>年龄：<%=ageapplicationString%><br> <a href="JSP/Login.jsp">回到信息输入界面</a></div></body></html>

在这个页面中，我们对request,pageContext,session,application的属性进行设置，修改。

其次还有一个页面，可以帮助我们完成测试：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%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>fourjsp 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>  <%  String namepageContextString = (String)pageContext.getAttribute("name");  String namesessionString = (String)session.getAttribute("name");  String namerequestString = (String)request.getAttribute("name");  String nameapplicationString = (String)application.getAttribute("name");  String pswdpageContextString = (String)pageContext.getAttribute("pswd");  String pswdsessionString = (String)session.getAttribute("pswd");  String pswdrequestString = (String)request.getAttribute("pswd");  String pswdapplicationString = (String)application.getAttribute("pswd");  String sexpageContextString = (String)pageContext.getAttribute("sex");  String sexsessionString = (String)session.getAttribute("sex");  String sexrequestString = (String)request.getAttribute("sex");  String sexapplicationString = (String)application.getAttribute("sex");  String agepageContextString = (String)pageContext.getAttribute("age");  String agesessionString = (String)session.getAttribute("age");  String agerequestString = (String)request.getAttribute("age");  String ageapplicationString = (String)application.getAttribute("age");   %>    客户信息：<br>    pageContext:<br>    姓名：<%=namepageContextString %><br>    密码：<%=pswdpageContextString %><br>    性别：<%=sexpageContextString %><br>    年龄：<%=agepageContextString %><br>    session:<br>    姓名：<%=namesessionString %><br>    密码：<%=pswdsessionString %><br>    性别：<%=sexsessionString %><br>    年龄：<%=agesessionString %><br>    request:<br>    姓名：<%=namerequestString %><br>    密码：<%=pswdrequestString %><br>    性别：<%=sexrequestString %><br>    年龄：<%=agerequestString %><br>    application:<br>    姓名：<%=nameapplicationString %><br>    密码：<%=pswdapplicationString %><br>    性别：<%=sexapplicationString %><br>    年龄：<%=ageapplicationString %><br>  </body></html>

接下来：

因为session并不会在关闭浏览器的时候，及时的销毁session对象，所以，我们在web.xml中进行设置自动销毁时间：

  <session-config>  <session-timeout>1</session-timeout>  </session-config>

然后启动项目，对这些事件进行监听：

当服务器开始启动时，就会创建一个application对象，然后服务器对application对象的属性进行操作：

为什么会有一个request对象被销毁呢？

因为浏览器打开有一个首页，但是我们需要浏览器跳转到指定的页面，所以手动的修改了url地址，只要url的地址发生改变，那么，就会产生一个request请求，那么就会有一个request请求被销毁。

因为我们新打开一个浏览器，所以就产生一个新的会话，就会创建一个新的session对象，当我们打开测试的页面时，因为在测试页面里对session，application等进行属性设置，修改，所以：

因为在jsp内部引入了jQuery文件，所以会发生request对象的销毁与新建：

这里是因为，我们设置了session的自动销毁时间是1分钟，所以当超过一分钟的时候，会自动的销毁session，此时如果刷新页面，则会：

到了这里，我们，对3大对象，6个事件八个接口进行了测试，可以检测到application创建销毁的接口，application属性改变的接口,request创建销毁的接口,request属性改变的接口，session创建销毁的接口，session属性改变的接口，以及session的active和Binding的接口事件。

所以，3大对象6种事件8个接口，到了这里就测试完毕了。