apache commons-io相关介绍-monitor包

mons.io.monitor 文件状态监控

mons.io.monitor包的作用监控指定目录下的文件状态。它使用观察者设计模式设计这些类的关系。当文件创建，文件修改和文件删除事件发生时会调用相应的回调函数。

基本使用方法：

package com.demo.monitor;import java.io.File;import mons.io.monitor.FileAlterationListener;import mons.io.monitor.FileAlterationMonitor;import mons.io.monitor.FileAlterationObserver;public class Demo1 {public static void main(String[] args) throws Exception {File directory = new File(new File("."), "src");FileAlterationObserver observer = new FileAlterationObserver(directory);observer.addListener(new MyFileAlterationListener());long interval = 1000;FileAlterationMonitor monitor = new FileAlterationMonitor(interval);monitor.addObserver(observer);monitor.start();}public static class MyFileAlterationListener implementsFileAlterationListener {public void onStart(FileAlterationObserver observer) {// TODO Auto-generated method stubSystem.out.println("--------onStart ---------");}public void onDirectoryCreate(File directory) {// TODO Auto-generated method stubSystem.out.println("--------onDirectoryCreate ---------");}public void onDirectoryChange(File directory) {// TODO Auto-generated method stubSystem.out.println("--------onDirectoryChange ---------");}public void onDirectoryDelete(File directory) {// TODO Auto-generated method stubSystem.out.println("--------onDirectoryDelete ---------");}public void onFileCreate(File file) {// TODO Auto-generated method stubSystem.out.println("--------onFileCreate ---------");}public void onFileChange(File file) {// TODO Auto-generated method stubSystem.out.println("--------onFileChange ---------");}public void onFileDelete(File file) {// TODO Auto-generated method stubSystem.out.println("--------onFileDelete ---------");}public void onStop(FileAlterationObserver observer) {// TODO Auto-generated method stubSystem.out.println("--------onStop ---------");}}

}

monitor.start();开启监控器，每隔interval毫秒，onStart会被执行一次，直接结束时，onStop将会被调用。Listener的创建过程以上代码是直接继承了FileAlterationListener接口，所有的接口函数必须被实现。这个过程比较繁琐。当调用者只关心其中一些事件却不得不实现所有函数。简化的方法是使用程序提供的一个适配器类FileAlterationListenerAdaptor（这里使用了适配器模式）。这样调用者只需重写关注的事件函数，大大简化了代码。代码如下：

package com.demo.monitor;import java.io.File;import mons.io.monitor.FileAlterationListener;import mons.io.monitor.FileAlterationListenerAdaptor;import mons.io.monitor.FileAlterationMonitor;import mons.io.monitor.FileAlterationObserver;public class Demo2 {public static void main(String[] args) throws Exception {File directory = new File(new File("."), "src");FileAlterationObserver observer = new FileAlterationObserver(directory);observer.addListener(new FileAlterationListenerAdaptor(){@Overridepublic void onFileCreate(File file) {System.out.println("---------onFileCreate--------");}});long interval = 1000;FileAlterationMonitor monitor = new FileAlterationMonitor(interval);monitor.addObserver(observer);monitor.start();}}