监听器Listener
监听器
6个事件类，均以event结尾
*某些操作，如启动/关闭容器，创建/销毁会话，都将触发一种事件发生，当发生了某种事件，容器将创建对应的事件类对象
8个监听接口，均以Listener结尾
监听器定义了监听方法，可以处理对应的事件
ServletAPI中的6个事件类：
ServletContextEvent：该类表示上下文（ServletContext）事件，当应用上下文对象发生变化，如创建或销毁上下文对象时，将触发上下文事件
ServletContextAttributeEvent：该类表示上下文（ServletContext）属性事件，当应用上下文属性改变，例如增加、删除、覆盖上下文中的属性时，将触发上下文属性事件
ServletRequestEvent：该类表示请求（ServletRequest）事件，当请求对象发生改变，例如创建或者销毁请求对象，将触发此事件
ServletRequestAttributeEvent：该类表示请求（ServletRequest）属性事件，当请求中的属性发生改变，触发该事件
HttpSessionEvent：该类表示会话（HttpSession）事件，当会话对象发生改变，例如创建或者销毁会话对象，活化或者钝化会话对象，将触发此事件
HttpSessionBindingEvent：该类表示会话（HttpSession）绑定事件，当会话中的属性发生变化，例如增加删除覆盖会话中
Servlet API针对每种事件类型，都定义了至少一种借口来处理该事件，这些接口都以Listener结尾，成为监听器接口，共有如下8种接口。
ServletConetxListener：上下文监听器，监听ServletContextEvent事件
ServletContextaAttributeListener：上下文属性监听器，用来监听ServletRequestAttributeEvent事件
ServletRequestListener：请求监听器，监听ServletRequestEvent事件。
ServletRequestAttributeListener:请求属性监听器，用来监听ServletRequestAttributeEvent事件
HttpSessionListener：会话监听器，监听HttpSessionEvent事件
HttpSessionActivationListener：会话活化监听器，监听HttpSessionEvent事件
HttpSessionAttributeListener：会话属性监听器，监听HttpSessionBindingEvent事件
HttpSessionBindingListener：会话绑定监听器，监听HttpSessionBindingEvent事件。
使用监听器的小例子：
计算登录次数：
package cn.itcast.service; import javax.servlet.ServletContext; import javax.servlet.ServletContextEvent; import javax.servlet.ServletContextListener; public class CounterListener implements ServletContextListener{ public void contextDestroyed(ServletContextEvent arg0) { System.out.println("我是销毁方法"); ServletContext context=arg0.getServletContext(); CounterService countService=new CounterService(); countService.saveNub((Integer) context.getAttribute("counter")); } public void contextInitialized(ServletContextEvent arg0) { ServletContext context=arg0.getServletContext(); CounterService countService=new CounterService(); context.setAttribute("counter",countService.getNub() ); } } <listener> <listener-class>cn.itcast.service.CounterListener</listener-class> </listener>
使用监听器开发的步骤：
1、根据实际情况，选择需要使用的监听器，如监听上下文对象创建或销毁的事件，则使用ServletContextListener
2、创建新的类，实现选择的监听器接口，兵书写具体实现代码
3、在web.xml中配置监听器
上面的例子全貌：
create table counter ( nub integer not null unique ) package cn.itcast.dao; import org.hibernate.Query; import org.hibernate.Session; import cn.itcast.domain.Counter; import cn.itcast.utils.SessionFactoryUtil; public class CounterDao { public Session getSession(){ return SessionFactoryUtil.getSession(); } public void saveNub(int nub){ String hql="update Counter set nub=?"; Query query=getSession().createQuery(hql); query.setParameter(0, nub); query.executeUpdate(); } public int getNub(){ String hql="from Counter"; Query query=getSession().createQuery(hql); Counter count=(Counter) query.uniqueResult(); return count.getNub(); } } package cn.itcast.domain; import java.io.Serializable; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.Table; @Table @Entity public class Counter implements Serializable{ private static final long serialVersionUID = 1L; private int nub; @Column public int getNub() { return nub; } public void setNub(int nub) { this.nub = nub; } public Counter(){ } public Counter(int nub){ this.nub=nub; } } <?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="cn.itcast.domain.Counter" table="COUNTER"> <composite-id> <key-property name="nub" column="nub" type="java.lang.Integer"/> </composite-id> </class> </hibernate-mapping> package cn.itcast.service; import javax.servlet.ServletContext; import javax.servlet.ServletContextEvent; import javax.servlet.ServletContextListener; public class CounterListener implements ServletContextListener{ public void contextDestroyed(ServletContextEvent arg0) { System.out.println("我是销毁方法"); ServletContext context=arg0.getServletContext(); CounterService countService=new CounterService(); countService.saveNub((Integer) context.getAttribute("counter")); } public void contextInitialized(ServletContextEvent arg0) { ServletContext context=arg0.getServletContext(); CounterService countService=new CounterService(); context.setAttribute("counter",countService.getNub() ); } } package cn.itcast.service; import org.hibernate.Transaction; import cn.itcast.dao.CounterDao; public class CounterService { private CounterDao counterDao=new CounterDao(); public int getNub(){ return counterDao.getNub(); } public void saveNub(int nub){ Transaction transaction=counterDao.getSession().beginTransaction(); try{ counterDao.saveNub(nub); transaction.commit(); }catch(Exception e){ e.printStackTrace(); transaction.rollback(); } } } package cn.itcast.test; import org.junit.Test; import cn.itcast.service.CounterService; import cn.itcast.utils.SessionFactoryUtil; @SuppressWarnings("unused") public class Test01 { @Test public void test1() { SessionFactoryUtil su=new SessionFactoryUtil(); } @Test public void test2(){ CounterService counterService=new CounterService(); counterService.saveNub(-1); System.out.println(counterService.getNub()); } } package cn.itcast.utils; import java.io.IOException; import javax.servlet.Filter; import javax.servlet.FilterChain; import javax.servlet.FilterConfig; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.ServletResponse; /** * 字符编码过滤器 * @author Administrator * */ public class CharacterEncodingFilter implements Filter{ private String encoding; public void destroy() { } public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2) throws IOException, ServletException { arg0.setCharacterEncoding(encoding); arg1.setCharacterEncoding(encoding); arg2.doFilter(arg0, arg1); } public void init(FilterConfig arg0) throws ServletException { this.encoding=arg0.getInitParameter("encoding"); } } package cn.itcast.utils; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.cfg.Configuration; import org.hibernate.service.ServiceRegistry; import org.hibernate.service.ServiceRegistryBuilder; public class SessionFactoryUtil { private static SessionFactory factory; private static ThreadLocal<Session> threadLocal=new ThreadLocal<Session>(); static{ Configuration config=new Configuration().configure(); ServiceRegistry resgistry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry(); factory=config.buildSessionFactory(resgistry); } public static Session getSession(){ Session session=threadLocal.get(); if(session==null){ session=factory.openSession(); threadLocal.set(session); } return session; } } package cn.itcast.utils; import java.awt.BasicStroke; import java.awt.Color; import java.awt.Font; import java.awt.Graphics2D; import java.awt.image.BufferedImage; import java.io.IOException; import java.io.OutputStream; import java.util.Random; import javax.imageio.ImageIO; public class VerifyCode { private int w=70; private int h=35; private Random r=new Random(); private String[] fontNames={"宋体","华文楷体","微软雅体","楷体_GB2312"}; private String codes="23456789abdcefghjkmnopqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ"; private Color bgColor=new Color(255,255,255); private String text; private Color randomColor(){ int red=r.nextInt(150); int green=r.nextInt(150); int blue=r.nextInt(150); return new Color(red,green,blue); } public char randomChar(){ return codes.charAt(r.nextInt(codes.length())); } private Font randomFont(){ int index=r.nextInt(fontNames.length); String fontName=fontNames[index]; int style=r.nextInt(4); int size=r.nextInt(5)+24; return new Font(fontName,style,size); } private void drawLine(BufferedImage image){ int num=3; Graphics2D g2=(Graphics2D)image.getGraphics(); for(int i=0;i<num;i++){ int x1=r.nextInt(w); int y1=r.nextInt(h); int x2=r.nextInt(w); int y2=r.nextInt(h); g2.setStroke(new BasicStroke(1.5F)); g2.setColor(Color.BLUE); g2.drawLine(x1, y1, x2, y2); } } private BufferedImage createImage(){ BufferedImage bi=new BufferedImage(w,h,BufferedImage.TYPE_INT_RGB); Graphics2D g2=(Graphics2D)bi.createGraphics(); g2.setColor(bgColor); g2.fillRect(0, 0, w, h); return bi; } private void setText(String text){ this.text=text; } public String getText(){ return text; } public BufferedImage getImage(){ BufferedImage image=createImage(); Graphics2D g2=(Graphics2D)image.createGraphics(); StringBuilder sb=new StringBuilder(); for(int i=0;i<4;i++){ String s=randomChar()+""; sb.append(s); float x=i*1.0F*w/4; g2.setFont(randomFont()); g2.setColor(randomColor()); g2.drawString(s, x, h-5); } this.setText(sb.toString()); drawLine(image); return image; } public static void output(BufferedImage image,OutputStream out){ try { ImageIO.write(image, "JPEG", out); } catch (IOException e) { e.printStackTrace(); } } } package cn.itcast.web; import java.awt.image.BufferedImage; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import cn.itcast.utils.VerifyCode; @SuppressWarnings("static-access") public class CheckCodeServlet extends HttpServlet { private static final long serialVersionUID = 1L; public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request,response); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { VerifyCode verify=new VerifyCode(); BufferedImage image=verify.getImage(); String text=verify.getText(); request.getSession().setAttribute("checkCode", text); verify.output(image, response.getOutputStream()); } } package cn.itcast.web; import java.io.IOException; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class LoginServlet extends HttpServlet { private static final long serialVersionUID = 1L; public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request,response); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { ServletContext context=this.getServletContext(); String name=request.getParameter("username"); String password=request.getParameter("password"); String checkCode=request.getParameter("checkCode"); String text=(String) request.getSession().getAttribute("checkCode"); int x=(Integer) context.getAttribute("counter")+1; System.out.println(name+" "+password+" "+checkCode+" "+text); context.setAttribute("counter", x); request.setAttribute("loginName",name); request.getRequestDispatcher("/success.jsp").forward(request, response); } } <?xml version='1.0' encoding='utf-8'?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <!-- Database connection settings --> <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property> <property name="connection.url">jdbc:oracle:thin:@localhost:1521:DB</property> <property name="connection.username">scott</property> <property name="connection.password">961012gz</property> <property name="dialect">org.hibernate.dialect.OracleDialect</property> <property name="show_sql">true</property> <!-- <mapping class="cn.itcast.domain.Counter"/> --> <mapping resource="cn/itcast/domain/Counter.hbm.xml"/> </session-factory> </hibernate-configuration> <?xml version="1.0" encoding="UTF-8"?> <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <display-name></display-name> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> <servlet> <servlet-name>checkCodeServlet</servlet-name> <servlet-class>cn.itcast.web.CheckCodeServlet</servlet-class> </servlet> <servlet> <description>This is the description of my J2EE component</description> <display-name>This is the display name of my J2EE component</display-name> <servlet-name>LoginServlet</servlet-name> <servlet-class>cn.itcast.web.LoginServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>checkCodeServlet</servlet-name> <url-pattern>/checkCode</url-pattern> </servlet-mapping> <servlet-mapping> <servlet-name>LoginServlet</servlet-name> <url-pattern>/login</url-pattern> </servlet-mapping> <filter> <filter-name>CharacterEncoding</filter-name> <filter-class>cn.itcast.utils.CharacterEncodingFilter</filter-class> <init-param> <param-name>encoding</param-name> <param-value>utf-8</param-value> </init-param> </filter> <filter-mapping> <filter-name>CharacterEncoding</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <listener> <listener-class>cn.itcast.service.CounterListener</listener-class> </listener> </web-app> <%@ 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>My JSP 'login.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"> --> <script> function change(){ var img=document.getElementsByName("img")[0]; img.src="checkCode?date="+new Date().getTime(); } </script> </head> <body> <form action="login" method="post"> 用户名：<input type="text" name="username"><br/> 密码：<input type="password" name="password"><br/> 验证码：<input type="text" size="5" name="checkCode"/><img src="checkCode" name="img"><a href="javascript:void(0)" onclick="change()">刊不清，换一张</a><br/> <input type="submit" value="登录"> </form> </body> </html> <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <% 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 'success.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> 欢迎${requestScope.loginName }莅临本系统<br/> <p align="right">访问量${applicationScope.counter }</p> </body> </html>
Listener: 监听器
1、初次见面：AWT
2、二次见面：SAX
监听器：
它是一个接口，内容由我们来实现
它需要注册，例如注册在按钮上
监听器中的方法，会在特殊事件发生时被调用！
观察着：
事件源
小偷
事件
偷东西
监听器
警察
监听器中的方法：抓捕
javaWeb中的监听器
事件源：三大域
ServletContext
生命周期监听：ServletContextListener，它有两个方法，一个在出生时调用，一个在死亡时调用；
属性监听：ServletContextAttributeListener，它有三个方法，一个是在添加属性的时候调用，一个是在替换属性的时候调用，一个是在移除属性时调用
HttpSession
生命周期监听：HttpSessionListener，它有两个方法，一个在出生时调用，一个在死亡时调用；
属性监听：HttpSessionAttributeListener，它有三个方法，一个是在添加属性的时候调用，一个是在替换属性的时候调用，一个是在移除属性时调用
ServletRequest
生命周期监听：ServletRequestListener，它有两个方法，一个在出生时调用，一个在死亡时调用；
属性监听：ServletRequestAttributeListener，它有三个方法，一个是在添加属性的时候调用，一个是在替换属性的时候调用，一个是在移除属性时调用
javaWeb中完成编写监听器：
写一个监听器类：要求必须去实现某个监听器接口
注册，是在web.xml中配置来完成
一个生命周期监听和属性监听例子：
package cn.itcast.web.listener; import javax.servlet.ServletContextEvent; import javax.servlet.ServletContextListener; /** * ServletContext生死监听 * @author Administrator * * 可以在这个监听器存放一些在tomcat启动时就要完成的代码！ * */ public class Alistener implements ServletContextListener { public void contextDestroyed(ServletContextEvent arg0) { System.out.println("我还会再回来的！"); } public void contextInitialized(ServletContextEvent arg0) { System.out.println("我胡汉三又回来了"); } } package cn.itcast.web.listener; import javax.servlet.ServletContextAttributeEvent; import javax.servlet.ServletContextAttributeListener; public class Blistener implements ServletContextAttributeListener{ public void attributeAdded(ServletContextAttributeEvent arg0) { System.out.println("您向application中添加了一个名为"+arg0.getName()+",值为："+arg0.getValue()+"的属性"); } public void attributeRemoved(ServletContextAttributeEvent arg0) { System.out.println(arg0.getName()+"="+arg0.getValue());//最后一次相见 } public void attributeReplaced(ServletContextAttributeEvent arg0) { System.out.println(arg0.getName()+ "="+arg0.getValue()+","+arg0.getServletContext().getAttribute(arg0.getName()));//返回的是之前的值，最后一次相见 } } <listener> <listener-class>cn.itcast.web.listener.Alistener</listener-class> </listener> <listener> <listener-class>cn.itcast.web.listener.Blistener</listener-class> </listener> <%@ 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>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> <% application.setAttribute("xxx", "XXX"); %> This is my JSP page. <br> </body> </html> <%@ 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>My JSP 'remove.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> <% application.removeAttribute("xxx"); %> This is my JSP page. <br> </body> </html> <%@ 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>My JSP 'repeat.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> <% application.setAttribute("xxx", "YYY"); %> </body> </html>
另外两个监听：感知监听（与HttpSession相关）
它用来添加到javaBean上，而不是添加到三大域
无需在web.xml注册
HttpSessionBindingListener:添加到javabean上，javabean就知道自己是否添加到session中了
监听bean添加到session的例子：
package cn.itcast.web.listener; import javax.servlet.http.HttpSessionBindingEvent; import javax.servlet.http.HttpSessionBindingListener; public class User implements HttpSessionBindingListener { 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 User() { super(); // TODO Auto-generated constructor stub } public User(String username, String password) { super(); this.username = username; this.password = password; } public void valueBound(HttpSessionBindingEvent arg0) { System.out.println("啊，session添加了我！"); } public void valueUnbound(HttpSessionBindingEvent arg0) { System.out.println("啊，无情的session抛弃了我！"); } } <%@ page language="java" import="java.util.*,cn.itcast.web.listener.User" 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>My JSP 'add.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> <% User user=new User("gz","6545"); session.setAttribute("user", user); %> </body> </html> <%@ 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>My JSP 'remove.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> <% session.removeAttribute("user"); %> </body> </html>
session的序列化：
程序有session的时候，意外关闭程序，会自动将session的序列化文件保存起来。重启项目，序列化文件消失，之前的session加载回服务器
存放文件夹例子：E:\anzhuang\tomcat7\apache-tomcat-7.0.70-windows-x86\apache-tomcat-7.0.70\work\Catalina\localhost\8-2_2
文件例子：SESSIONS.ser
废弃session的序列化：
在context.xml中的<Context>标签体内加上
<Manager pathname="" />
Session的钝化和活化：
在一些比较大的网站的时候，访问量过多的话，可能会导致系统占用内存过多。一中利用session钝化优化的手段，就是在context中设置session自动钝化，也就是说在一段时间内，
如果session没有被访问，session就被序列化到硬盘上，再次使用该session的时候，session自动从硬盘上反序列化到内存中。
在Context中设置：
<Manager className="org.apache.catalina.session.PersistentManager" maxIdleSwap="1"><!-- maxIdleSwap代表session的钝化周期，单位分钟 -->
<Store CLASSnAME="org.apache.catalina.session.FileStore" directory="mysession"/><!-- session的序列化文件的存放路径 -->
</manager>
HttpSessionActivationListener:添加到javabean上，监听bean随着session的钝化活化的过程
最后一个监听，监听bean的钝化和活化过程：
package cn.itcast; import java.io.Serializable; import javax.servlet.http.HttpSessionActivationListener; import javax.servlet.http.HttpSessionEvent; public class User implements HttpSessionActivationListener,Serializable { /** * */ private static final long serialVersionUID = 1L; /** * 注意：这个User必须实现序列化接口，否则无法写入硬盘 */ public void sessionDidActivate(HttpSessionEvent arg0) { System.out.println("啊，~我和session一起重返地球了！"); } public void sessionWillPassivate(HttpSessionEvent arg0) { System.out.print("啊，~我陪session去火星了，地球已经不安全了！"); } } <%@ page language="java" import="java.util.*,cn.itcast.User" 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>My JSP 'a.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> <h1>向session中保存数据</h1> <% session.setAttribute("xxx", "我是一只快乐的小session"); session.setAttribute("yyy",new User()); %> </body> </html> <%@ 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>My JSP 'b.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> <h2>获取session中的数据</h2> <% /* out.print(session.getAttribute("xxx")); */ out.println(session.getAttribute("yyy")); %> </body> </html> context中的配置： <Manager className="org.apache.catalina.session.PersistentManager" maxIdleSwap="1"> <Store className="org.apache.catalina.session.FileStore" directory="mysession"/> </Manager>
