继续接着监听器的分类进行，来看第二种分类中的第二小类。
MyServletContextAttributeListener.java源代码：
package com.listener; import javax.servlet.ServletContextAttributeEvent; import javax.servlet.ServletContextAttributeListener; import javax.servlet.annotation.WebListener; /** * Application Lifecycle Listener implementation class MyServletContextAttributeListener * */ @WebListener public class MyServletContextAttributeListener implements ServletContextAttributeListener { /** * Default constructor. */ public MyServletContextAttributeListener() { } /** * @see ServletContextAttributeListener#attributeAdded(ServletContextAttributeEvent) */ public void attributeAdded(ServletContextAttributeEvent servletContextAttributeEvent) { System.out.println("ServletContext_attributeAdded:"+servletContextAttributeEvent.getName()); } /** * @see ServletContextAttributeListener#attributeRemoved(ServletContextAttributeEvent) */ public void attributeRemoved(ServletContextAttributeEvent servletContextAttributeEvent) { System.out.println("ServletContext_attributeRemoved:"+servletContextAttributeEvent.getName()); } /** * @see ServletContextAttributeListener#attributeReplaced(ServletContextAttributeEvent) */ public void attributeReplaced(ServletContextAttributeEvent servletContextAttributeEvent) { System.out.println("ServletContext_attributeReplaced:"+servletContextAttributeEvent.getName()); } }
MyHttpSessionAttributeListener.java源代码：
package com.listener; import javax.servlet.annotation.WebListener; import javax.servlet.http.HttpSessionAttributeListener; import javax.servlet.http.HttpSessionBindingEvent; /** * Application Lifecycle Listener implementation class MyHttpSessionAttributeListener * */ @WebListener public class MyHttpSessionAttributeListener implements HttpSessionAttributeListener { /** * Default constructor. */ public MyHttpSessionAttributeListener() { } /** * @see HttpSessionAttributeListener#attributeAdded(HttpSessionBindingEvent) */ public void attributeAdded(HttpSessionBindingEvent sessionBindingEvent) { System.out.println("HttpSession_attributeAdded:"+sessionBindingEvent.getName()); } /** * @see HttpSessionAttributeListener#attributeRemoved(HttpSessionBindingEvent) */ public void attributeRemoved(HttpSessionBindingEvent sessionBindingEvent) { System.out.println("HttpSession_attributeRemoved:"+sessionBindingEvent.getName()); } /** * @see HttpSessionAttributeListener#attributeReplaced(HttpSessionBindingEvent) */ public void attributeReplaced(HttpSessionBindingEvent sessionBindingEvent) { System.out.println("HttpSession_attributeReplaced:"+sessionBindingEvent.getName()); } }
ServletRequestAttributeListener.java源代码：
package com.listener; import javax.servlet.ServletRequestAttributeEvent; import javax.servlet.ServletRequestAttributeListener; import javax.servlet.annotation.WebListener; /** * Application Lifecycle Listener implementation class MyServletRequestAttributeListener * */ @WebListener public class MyServletRequestAttributeListener implements ServletRequestAttributeListener { /** * Default constructor. */ public MyServletRequestAttributeListener() { } /** * @see ServletRequestAttributeListener#attributeRemoved(ServletRequestAttributeEvent) */ public void attributeRemoved(ServletRequestAttributeEvent servletRequestAttributeEvent) { System.out.println("ServletRequest_attributeRemoved:"+servletRequestAttributeEvent.getName()); } /** * @see ServletRequestAttributeListener#attributeAdded(ServletRequestAttributeEvent) */ public void attributeAdded(ServletRequestAttributeEvent servletRequestAttributeEvent) { System.out.println("ServletRequest_attributeAdded:"+servletRequestAttributeEvent.getName()); } /** * @see ServletRequestAttributeListener#attributeReplaced(ServletRequestAttributeEvent) */ public void attributeReplaced(ServletRequestAttributeEvent servletRequestAttributeEvent) { System.out.println("ServletRequest_attributeReplaced:"+servletRequestAttributeEvent.getName()); } }
我们使用的JSP页面包括：
index.jsp页面：
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title here</title> </head> <body> <h1>我是JSP页面</h1> <hr/> <button οnclick="location.href='<%=request.getContextPath()%>/init.jsp';">Init</button> <button οnclick="location.href='<%=request.getContextPath()%>/destory.jsp';">Destory</button> </body> </html>
init.jsp页面：
<%@page import="com.domain.Admin"%> <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title here</title> </head> <body> <h1>这是初始化值的页面</h1> <hr/> <% request.setAttribute("requestName", "requestValue"); request.getSession().setAttribute("sessionName", "sessionValue"); request.getSession().getServletContext().setAttribute("contextName", "contextValue"); %> <button οnclick="location.href='<%=request.getContextPath()%>/init.jsp';">Init</button> <button οnclick="location.href='<%=request.getContextPath()%>/destory.jsp';">Destory</button> </body> </html>
destory.jsp页面：
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title here</title> </head> <body> <h1>这是销毁值的页面</h1> <hr/> <% request.removeAttribute("requestName"); request.getSession().removeAttribute("sessionName"); request.getSession().getServletContext().removeAttribute("contextName"); %> <button οnclick="location.href='<%=request.getContextPath()%>/init.jsp';">Init</button> <button οnclick="location.href='<%=request.getContextPath()%>/destory.jsp';">Destory</button> </body> </html>
运行结果：
我们通过访问index页面开始：
点击init按钮：
再次点击init按钮：
点击destory按钮：
我们来看第三小类。
本质就在于把服务器中不经常使用的Session对象暂时序列化到系统文件系统或者数据库系统中，当使用时反序
列化到内存中，整个过程由服务器自动完成。使用的并不是很多。
示意图：
Tomcat中两种session钝化管理器
session钝化机制由SessionManager管理。
第一种：
第二种：
Servlet规范
包括两个监听器，都不需要再web.xml中注册。
绑定：vlaueBound()方法
解除绑定：valueUnbound()方法
钝化：sessionWillPassivate()方法
活化：sessionDidActivate()方法
只提供上述两个监听器的实例源码：
package com.domain; import java.io.Serializable; import javax.servlet.http.HttpSessionActivationListener; import javax.servlet.http.HttpSessionBindingEvent; import javax.servlet.http.HttpSessionBindingListener; import javax.servlet.http.HttpSessionEvent; public class User implements HttpSessionBindingListener,HttpSessionActivationListener,Serializable { private String username; private String password; public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public void valueBound(HttpSessionBindingEvent httpsessionbindingevent) { System.out.println("valueBound Name:"+httpsessionbindingevent.getName()); } public void valueUnbound(HttpSessionBindingEvent httpsessionbindingevent) { System.out.println("valueUnbound Name:"+httpsessionbindingevent.getName()); } public void sessionWillPassivate(HttpSessionEvent httpsessionevent) { System.out.println("sessionWillPassivate "+httpsessionevent.getSource()); } public void sessionDidActivate(HttpSessionEvent httpsessionevent) { System.out.println("sessionDidActivate "+httpsessionevent.getSource()); } } 我们在init页面和destory页面使用request对象添加User对象实例，就可以测试了。
