课时12 什么叫监听器Listener
AWT、SAX
监听器：
一个接口，内容由用户实现
需要注册
监听器中的方法，会在特殊事件发生时被调用
观察者
事件源
事件
监听器
课时13 监听器概述以及生命周期监听器
事件源
1、ServletContext 生命周期监听 ServletContextListener 创建 contextInitialized 销毁 contextDestroyed ServletContextEvent -getServletContext() 属性监听 ServletContextAttributeListener 添加 attributeAdded 替换 attributeReplaced 移除 attributeRemoved ServletContextAttributeEvent -getName() -getValue() 2、HttpSession 生命周期监听 HttpSessionListener 创建 sessionCreated 销毁 sessionDestroyed HttpSessionEvent -getSession() 属性监听 HttpSessionAttributeListener 添加 attributeAdded 替换 attributeReplaced 移除 attributeRemoved HttpSessionBindingEvent -getSession() -getName() -getValue() 3、ServletRequest 生命周期监听 ServletRequestListener 创建 requestDestroyed 销毁 requestInitialized ServletRequestEvent -getServletRequest() -getServletContext() 属性监听 ServletRequestAttributeListener 添加 attributeAdded 替换 attributeReplaced 移除 attributeRemoved ServletRequestAttributeEvent -getName() -getValue()
编写监听器
继承父类，实现方法
package com.pengshiyu.listener; import javax.servlet.ServletContextEvent; import javax.servlet.ServletContextListener; public class AListener implements ServletContextListener{ @Override public void contextInitialized(ServletContextEvent sce) { } @Override public void contextDestroyed(ServletContextEvent sce) { } }
配置监听器web.xml
<listener> <listener-class>com.pengshiyu.listener.AListener</listener-class> </listener>
课时14 监听器之属性监听器
设置属性
package com.pengshiyu.servlet; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; public class AServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { getServletContext().setAttribute("key", "value"); response.getWriter().print("Hello"); } }
监听属性变化
package com.pengshiyu.listener; import javax.servlet.ServletContextAttributeEvent; import javax.servlet.ServletContextAttributeListener; public class AListener implements ServletContextAttributeListener { @Override public void attributeAdded(ServletContextAttributeEvent event) { System.out.println(event.getName() + ":" + event.getValue()); } @Override public void attributeRemoved(ServletContextAttributeEvent event) { System.out.println(event.getName() + ":" + event.getValue()); } @Override public void attributeReplaced(ServletContextAttributeEvent event) { System.out.println(event.getName() + ":" + event.getValue() + "->" + event.getServletContext().getAttribute(event.getName())); } }
课时15 感知监听器
都与HttpSession相关
添加到JavaBean上
不需要再web.xml中注册
package com.pengshiyu.bean; import javax.servlet.http.HttpSessionBindingEvent; import javax.servlet.http.HttpSessionBindingListener; public class User implements HttpSessionBindingListener { private String name; @Override public void valueBound(HttpSessionBindingEvent event) { System.out.println("session值绑定了: " + event.getName() + "=" + event.getValue()); } @Override public void valueUnbound(HttpSessionBindingEvent event) { System.out.println("session值解除绑定了: " + event.getName() + "=" + event.getValue()); } }
package com.pengshiyu.servlet; import com.pengshiyu.bean.User; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; public class AServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { User user = new User(); request.getSession().setAttribute("user", user); response.getWriter().print("Hello"); } }
课时16 session的序列化
session会在程序关闭的时候序列化到硬盘
再次启动程序，硬盘上的session会反序列化到内存
课时17 session的钝化和活化
<Context reloadable="true"> <Manager className="org.apche.catalina.session.PersistentManager" maxIdleSwap="1"> <Store className="org.apche.catalina.session.FileStore" directory="mysession"> </Store> </Manager> </Context>
钝化保存，活化重新加载
课时18 监听器之HttpSessionActivationListener
package com.pengshiyu.bean; import javax.servlet.http.HttpSessionActivationListener; import javax.servlet.http.HttpSessionEvent; public class User implements HttpSessionActivationListener, java.io.Serializable { @Override public void sessionWillPassivate(HttpSessionEvent se) { } @Override public void sessionDidActivate(HttpSessionEvent se) { } }
