Java实现实时监控目录下文件变化的方法

<!-- https://mvnrepository.com/artifact/commons-io/commons-io -->
<dependency>
  <groupId>commons-io</groupId>
  <artifactId>commons-io</artifactId>
  <version>2.6</version>
</dependency>

import java.io.File;
import org.apache.commons.io.monitor.FileAlterationListenerAdaptor;
import org.apache.commons.io.monitor.FileAlterationObserver;
import org.apache.log4j.Logger;
/**
 * 文件变化监听器
 * 在Apache的Commons-IO中有关于文件的监控功能的代码. 文件监控的原理如下：
 * 由文件监控类FileAlterationMonitor中的线程不停的扫描文件观察器FileAlterationObserver，
 * 如果有文件的变化，则根据相关的文件比较器，判断文件时新增，还是删除，还是更改。（默认为1000毫秒执行一次扫描）
 */
public class FileListener extends FileAlterationListenerAdaptor {
  private Logger log = Logger.getLogger(FileListener.class);
  /**
   * 文件创建执行
   */
  public void onFileCreate(File file) {
    log.info("[新建]:" + file.getAbsolutePath());
  }
  /**
   * 文件创建修改
   */
  public void onFileChange(File file) {
    log.info("[修改]:" + file.getAbsolutePath());
  }
  /**
   * 文件删除
   */
  public void onFileDelete(File file) {
    log.info("[删除]:" + file.getAbsolutePath());
  }
  /**
   * 目录创建
   */
  public void onDirectoryCreate(File directory) {
    log.info("[新建]:" + directory.getAbsolutePath());
  }
  /**
   * 目录修改
   */
  public void onDirectoryChange(File directory) {
    log.info("[修改]:" + directory.getAbsolutePath());
  }
  /**
   * 目录删除
   */
  public void onDirectoryDelete(File directory) {
    log.info("[删除]:" + directory.getAbsolutePath());
  }
  public void onStart(FileAlterationObserver observer) {
    // TODO Auto-generated method stub
    super.onStart(observer);
  }
  public void onStop(FileAlterationObserver observer) {
    // TODO Auto-generated method stub
    super.onStop(observer);
  }
}

public static void main(String[] args) throws Exception{
    // 监控目录
    String rootDir = "D:\\apache-tomcat-7.0.78";
    // 轮询间隔 5 秒
    long interval = TimeUnit.SECONDS.toMillis(1);
    // 创建过滤器
    IOFileFilter directories = FileFilterUtils.and(
        FileFilterUtils.directoryFileFilter(),
        HiddenFileFilter.VISIBLE);
    IOFileFilter files    = FileFilterUtils.and(
        FileFilterUtils.fileFileFilter(),
        FileFilterUtils.suffixFileFilter(".txt"));
    IOFileFilter filter = FileFilterUtils.or(directories, files);
    // 使用过滤器
    FileAlterationObserver observer = new FileAlterationObserver(new File(rootDir), filter);
    //不使用过滤器
    //FileAlterationObserver observer = new FileAlterationObserver(new File(rootDir));
    observer.addListener(new FileListener());
    //创建文件变化监听器
    FileAlterationMonitor monitor = new FileAlterationMonitor(interval, observer);
    // 开始监控
    monitor.start();
  }

public static void main(String[] a) {
    final Path path = Paths.get("D:\\apache-tomcat-7.0.78");
    try (WatchService watchService = FileSystems.getDefault().newWatchService()) {
      //给path路径加上文件观察服务
      path.register(watchService, StandardWatchEventKinds.ENTRY_CREATE,
          StandardWatchEventKinds.ENTRY_MODIFY,
          StandardWatchEventKinds.ENTRY_DELETE);
      while (true) {
        final WatchKey key = watchService.take();
        for (WatchEvent<?> watchEvent : key.pollEvents()) {
          final WatchEvent.Kind<?> kind = watchEvent.kind();
          if (kind == StandardWatchEventKinds.OVERFLOW) {
            continue;
          }
          //创建事件
          if (kind == StandardWatchEventKinds.ENTRY_CREATE) {
            System.out.println("[新建]");
          }
          //修改事件
          if (kind == StandardWatchEventKinds.ENTRY_MODIFY) {
            System.out.println("修改]");
          }
          //删除事件
          if (kind == StandardWatchEventKinds.ENTRY_DELETE) {
            System.out.println("[删除]");
          }
          // get the filename for the event
          final WatchEvent<Path> watchEventPath = (WatchEvent<Path>) watchEvent;
          final Path filename = watchEventPath.context();
          // print it out
          System.out.println(kind + " -> " + filename);
        }
        boolean valid = key.reset();
        if (!valid) {
          break;
        }
      }
    } catch (IOException | InterruptedException ex) {
      System.err.println(ex);
    }
  }