介绍

    本文主要介绍一种轻量级的文件监控方式，对文件的Create & Change & Delete，都有一个对应的Event方法来进行处理。对于核心的File Monitor Class，我们继承一个监听适配器类FileAlterationListenerAdaptor，这样会更方便，就不用再去重写每个Event方法。

File Generator Class

package shuai.study.file.generator;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Date;

import org.apache.log4j.Logger;

import shuai.study.file.tooler.CommonTooler;

/**
 * @author shengshu
 * 
 */
public class FileGenerator implements Runnable {
	private static final Logger LOG = Logger.getLogger(FileGenerator.class);

	private String directory = null;

	private static Date date = new Date();

	public FileGenerator(String directory) {
		this.directory = directory;
	}

	private void generator(String directory) {
		for (int i = 0; i < 10; i++) {
			String fileName = CommonTooler.getDateTimeFormat(date) + "-" + Thread.currentThread().getId() + i + ".pm";

			LOG.info("[Path]: " + directory + "/" + fileName);

			try {
				// Create file (path: directory/fileName)
				Files.createFile(Paths.get(directory, fileName));
			} catch (IOException ioe) {
				ioe.printStackTrace();
			}
		}
	}

	@Override
	public void run() {
		this.generator(directory);
	}
}

File Monitor Class

package shuai.study.file.monitor;

import java.io.File;
import java.io.IOException;

import org.apache.commons.io.FileUtils;
import org.apache.commons.io.FilenameUtils;
import org.apache.commons.io.filefilter.FileFilterUtils;
import org.apache.commons.io.monitor.FileAlterationListenerAdaptor;
import org.apache.commons.io.monitor.FileAlterationMonitor;
import org.apache.commons.io.monitor.FileAlterationObserver;
import org.apache.log4j.Logger;

import shuai.study.file.tooler.CommonTooler;

/**
 * @author shengshu
 * 
 */
public class FileMonitor extends FileAlterationListenerAdaptor {
	private static final Logger LOG = Logger.getLogger(FileMonitor.class);

	private static FileMonitor fileMonitor;

	private static int pageNumber = 0;

	private FileMonitor() {

	}

	// Get singleton object instance
	public static FileMonitor getFileMonitor() {
		if (fileMonitor == null) {
			synchronized (FileMonitor.class) {
				if (fileMonitor == null) {
					fileMonitor = new FileMonitor();
				}
			}
		}

		return fileMonitor;
	}

	// Create file event
	@Override
	public void onFileCreate(File file) {
		LOG.info("[Create]: " + file.getAbsolutePath());

		String fileAbsolutePath = file.getAbsolutePath();
		String fileAbsoluteParentPath = file.getParent();
		String fileBaseName = FilenameUtils.getBaseName(fileAbsolutePath);

		File destFile = new File(fileAbsoluteParentPath + File.separator + fileBaseName + "-" + CommonTooler.pagingFormat(pageNumber) + ".xml");

		try {
			FileUtils.moveFile(file, destFile);
		} catch (IOException ioe) {
			ioe.printStackTrace();
		}

		pageNumber++;
	}

	// Change file event
	@Override
	public void onFileChange(File file) {
		LOG.info("[Change]: " + file.getAbsolutePath());
	}

	// Delete file event
	@Override
	public void onFileDelete(File file) {
		LOG.info("[Delete]: " + file.getAbsolutePath());
	}

	public void monitor(String directory, int interval) {
		// Observer file whose suffix is pm 
		FileAlterationObserver fileAlterationObserver = new FileAlterationObserver(directory, FileFilterUtils.and(FileFilterUtils.fileFileFilter(),
				FileFilterUtils.suffixFileFilter(".pm")), null);

		// Add listener for event (file create & change & delete)
		fileAlterationObserver.addListener(this);

		// Monitor per interval
		FileAlterationMonitor fileAlterationMonitor = new FileAlterationMonitor(interval, fileAlterationObserver);

		try {
			// Start to monitor
			fileAlterationMonitor.start();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

File Tester Class

package shuai.study.file.tester;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;

import org.apache.log4j.Logger;

import shuai.study.file.generator.FileGenerator;
import shuai.study.file.monitor.FileMonitor;

/**
 * @author shengshu
 * 
 */
public class FileTester {
	private static final Logger LOG = Logger.getLogger(FileTester.class);

	private static String directory = "/home/omc/tmp";

	public static void main(String[] args) {
		// Create directory if it does not exist 
		try {
			Files.createDirectory(Paths.get(directory));
		} catch (IOException ioe) {
			ioe.printStackTrace();
		}

		LOG.info("File Monitor...");
		// Start to monitor file event per 500 milliseconds
		FileMonitor.getFileMonitor().monitor(directory, 500);

		LOG.info("File Generater...");
		// New runnable instance
		FileGenerator fileGeneratorRunnable = new FileGenerator(directory);

		// Start to multi-thread for generating file
		for (int i = 0; i < 10; i++) {
			Thread fileGeneratorThread = new Thread(fileGeneratorRunnable);
			fileGeneratorThread.start();
		}
	}

}

Common Tool Class

package shuai.study.file.tooler;

import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * @author shengshu
 * 
 */
public class CommonTooler {

	// Date time format
	public static String getDateTimeFormat(Date date) {
		SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyyMMdd-HHmm");
		String dateTime = simpleDateFormat.format(date);

		return dateTime;
	}

	// Page format
	public static String pagingFormat(int pageNumber) {
		String pageNumberStr = "P00";

		if (pageNumber < 0) {
			throw new NumberFormatException("The page number should not be negative");
		}

		if (pageNumber < 10) {
			pageNumberStr = String.format("P0%d", pageNumber);
		} else {
			pageNumberStr = String.format("P%d", pageNumber);
		}

		return pageNumberStr;
	}

}