java 监听文件或者文件夹变化的几种方式

１.log4j的实现的文件内容变化监听

package com.jp.filemonitor;
import org.apache.log4j.helpers.FileWatchdog;
public class Log4jWatchdog {
    public static void main(String[] args) {
        GloablConfig gloablConfig = new GloablConfig("D:\\create_lo\\text.txt");
        gloablConfig.setDelay(10000);
        gloablConfig.start();
        while (true) {
            try {
                Thread.sleep(10000);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }
    }
    public static class GloablConfig extends FileWatchdog{
        protected GloablConfig(String filename) {
            super(filename);
        }

        @Override
        protected void doOnChange() {

            System.out.println(filename);
        }

    }
}

２.common-io实现的文件夹变化的监听

这代码网上很多，可以搜索关键字FileAlterationMonitor，FileAlterationObserver　　FileAlterationObserver，这样就可以看到示例代码了。

３.nio实现文件夹内容变化的监听

package com.jp.filemonitor;

import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardWatchEventKinds;
import java.nio.file.WatchEvent;
import java.nio.file.WatchKey;
import java.nio.file.WatchService;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ResourceListener {
    private static ExecutorService fixedThreadPool = Executors.newCachedThreadPool();
    private WatchService ws;
    private String listenerPath;
    private ResourceListener(String path) {
        try {
            ws = FileSystems.getDefault().newWatchService();
            this.listenerPath = path;
            start();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void start() {
        fixedThreadPool.execute(new Listner(ws,this.listenerPath));
    }

    public static void addListener(String path) throws IOException {
        ResourceListener resourceListener = new ResourceListener(path);
        Path p = Paths.get(path);
        p.register(resourceListener.ws,StandardWatchEventKinds.ENTRY_MODIFY,
            StandardWatchEventKinds.ENTRY_DELETE,
            StandardWatchEventKinds.ENTRY_CREATE);
    }

    public static void main(String[] args) throws IOException {
        ResourceListener.addListener("F:\\");
        ResourceListener.addListener("d:\\");
    }
}

class Listner implements Runnable {
    private WatchService service;
    private String rootPath;

    public Listner(WatchService service,String rootPath) {
        this.service = service;
        this.rootPath = rootPath;
    }

    public void run() {
        try {
            while(true){
                WatchKey watchKey = service.take();
                List<WatchEvent<?>> watchEvents = watchKey.pollEvents();
                for(WatchEvent<?> event : watchEvents){

                    //TODO 根据事件类型采取不同的操作。。。。。。。
                    System.out.println("["+rootPath+event.context()+"]文件发生了["+event.kind()+"]事件"+    event.count());
                }
                watchKey.reset();
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }finally{
            System.out.println("fdsfsdf");
            try {
                service.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }
}