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>