Showing posts with label WatchService. Show all posts
Showing posts with label WatchService. Show all posts

Monday, September 26, 2016

File Change Listener Implementation Using Java


package com.pritom.kumar;

import java.io.File;
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;

/**
 * Created by pritom on 25/09/2016.
 */
public class ChangeFileListener {
    public static void main(String[] args) throws Exception {
        startWatch("C:/tmp");
    }

    public static void startWatch(String location) {
        try {
            Path directory = Paths.get(location);
            println("Start listening directory: [" + location + "]");
            final WatchService watchService = directory.getFileSystem().newWatchService();
            directory.register(watchService, StandardWatchEventKinds.ENTRY_CREATE, StandardWatchEventKinds.ENTRY_DELETE, StandardWatchEventKinds.ENTRY_MODIFY);

            while (true) {
                final WatchKey watchKey = watchService.take();
                handleWatchTriggered(location, watchKey);
                boolean valid = watchKey.reset();
                if (!valid) {
                    throw new Exception("Watcher failed for listen [" + location + "]");
                }
            }
        }
        catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    private static void handleWatchTriggered(String location, WatchKey watchKey) throws Exception {
        List<WatchEvent<?>> watchEventList = watchKey.pollEvents();
        for (WatchEvent watchEvent : watchEventList) {
            if (watchEvent.kind() == StandardWatchEventKinds.ENTRY_CREATE) {
                println("Created: [" + watchEvent.context().toString() + "]");
                File fileCreated = new File(location + "/" + watchEvent.context().toString());
            }
            else if (watchEvent.kind() == StandardWatchEventKinds.ENTRY_DELETE) {
                println("Deleted: [" + watchEvent.context().toString() + "]");
            }
            else if (watchEvent.kind() == StandardWatchEventKinds.ENTRY_MODIFY) {
                println("Modified: [" + watchEvent.context().toString() + "]");
            }
        }
    }

    public static void println(Object o) {
        System.out.println("" + o);
    }
}