ServletContextListener监听器

该监听器会在Servlet初始化前调用初始化方法。在Servlet销毁后调用销毁方法。

实例

监听器

package com.sea.listener;import com.sea.Count;
import org.omg.PortableInterceptor.Interceptor;import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import java.io.*;public class MyListener implements ServletContextListener {public void contextInitialized(ServletContextEvent sce) {System.out.println("初始化");ServletContext servletContext = sce.getServletContext();InputStream inputStream = servletContext.getResourceAsStream("/count/count.txt");InputStreamReader inputStreamReader = new InputStreamReader(inputStream);BufferedReader bufferedReader = new BufferedReader(inputStreamReader);Count count = new Count(0);try {System.out.println("a:");String s = bufferedReader.readLine();count.add(Integer.parseInt(s));} catch (IOException e) {e.printStackTrace();}servletContext.setAttribute("count",count);}public void contextDestroyed(ServletContextEvent sce) {System.out.println("销毁");ServletContext servletContext = sce.getServletContext();String path = servletContext.getRealPath("/count");path = path+"/count.txt";File file = new File(path);try {PrintWriter writer = new PrintWriter(file);Count count = (Count) servletContext.getAttribute("count");writer.println(count.getCount());System.out.println(count.getCount());writer.close();} catch (FileNotFoundException e) {e.printStackTrace();}}}

Web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"version="4.0"><servlet><servlet-name>MyServlet</servlet-name><servlet-class>com.sea.servlet.MyServlet</servlet-class><load-on-startup>0</load-on-startup></servlet><servlet-mapping><servlet-name>MyServlet</servlet-name><url-pattern>/my</url-pattern></servlet-mapping><--配置监听器!-><listener><listener-class>com.sea.listener.MyListener</listener-class></listener>
</web-app>

该实例可以实现访问计数的持久化