filter实现监听的三种方式

1方式一实现servletContextListener，代码如下：

package com.ask.listener;

import javax.servlet.ServletContextEvent;

import javax.servlet.ServletContextListener;

public class Demo1 implements ServletContextListener{

public Demo1(){

System.out.println("Demo1");

}

public void contextDestroyed(ServletContextEvent arg0) {

System.out.println("contextDestroyed");

}

public void contextInitialized(ServletContextEvent arg0) {

System.out.println("contextInitialized");

}

2. 方式二实现servletRequestListener，代码如下:

package com.ask.listener;

import javax.servlet.ServletRequestEvent;

import javax.servlet.ServletRequestListener;

public class Demo2 implements ServletRequestListener{

public Demo2(){

System.out.println("Demo2");

}

public void requestDestroyed(ServletRequestEvent arg0) {

System.out.println("requestDestroyed");

}

public void requestInitialized(ServletRequestEvent arg0) {

System.out.println("requestInitialized");

}

}

3. 方式三实现httpSessionListener，代码如下:

package com.ask.listener;

import javax.servlet.http.HttpSessionEvent;

import javax.servlet.http.HttpSessionListener;

public class Demo3 implements HttpSessionListener {

public Demo3(){

System.out.println("Demo3");

}

public void sessionCreated(HttpSessionEvent arg0) {

System.out.println("sessionCreated");

}

public void sessionDestroyed(HttpSessionEvent arg0) {

System.out.println("sessionDestroyed");

}

}

4.servlet中show类中代码如下:

package com.ask.servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

public class Show extends HttpServlet {

@Override

protected void service(HttpServletRequest req, HttpServletResponse res)

throws ServletException, IOException {

HttpSession session=req.getSession();

session.setMaxInactiveInterval(1);

System.out.println("实现监听的三种方式");

res.getWriter().write("实现监听的三种方式");

}

}

4. xml配置文件如下:

<?xml version="1.0"encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns="http://java.sun.com/xml/ns/javaee"xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"id="WebApp_ID"version="3.0">

<display-name>firstServlet</display-name>

<welcome-file-list>

<welcome-file>index.html</welcome-file>

<welcome-file>index.htm</welcome-file>

<welcome-file>index.jsp</welcome-file>

<welcome-file>default.html</welcome-file>

<welcome-file>default.htm</welcome-file>

<welcome-file>default.jsp</welcome-file>

</welcome-file-list>

<listener>

<listener-class>com.ask.listener.Demo1</listener-class>

</listener>

<listener>

<listener-class>com.ask.listener.Demo2</listener-class>

</listener>

<listener>

<listener-class>com.ask.listener.Demo3</listener-class>

</listener>

<servlet>

<servlet-name>show</servlet-name>

<servlet-class>com.ask.servlet.Show</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>show</servlet-name>

<url-pattern>/show</url-pattern>

</servlet-mapping>

</web-app>

5. 程序运行如下：先加载构造方法-在初始化-发送请求-创建session-请求结束