监视目录树

import java.io.IOException;

import java.nio.file.FileSystems;

import java.nio.file.FileVisitResult;

import java.nio.file.Files;
/*
nowjava - 时代Java 提供
*/

import java.nio.file.LinkOption;

import java.nio.file.Path;

import java.nio.file.Paths;

import java.nio.file.SimpleFileVisitor;

import java.nio.file.StandardWatchEventKinds;

import java.nio.file.WatchEvent;

import java.nio.file.WatchEvent.Kind;

import java.nio.file.WatchKey;

import java.nio.file.WatchService;

import java.nio.file.attribute.BasicFileAttributes;

import java.util.HashMap;

import java.util.Map;


class WatchRecursive {

  private WatchService watchService;

  private final Map<WatchKey, Path> directories = new HashMap<>();

  private void registerTree(Path start) throws IOException {
  /** 
   来自 时代Java公众号**/


    Files.walkFileTree(start, new SimpleFileVisitor<Path>() {


      @Override

      public FileVisitResult preVisitDirectory(Path dir,

          BasicFileAttributes attrs) throws IOException {

        System.out.println("Registering:" + dir);

        WatchKey key = dir.register(watchService,

            StandardWatchEventKinds.ENTRY_CREATE,

            StandardWatchEventKinds.ENTRY_MODIFY,

            StandardWatchEventKinds.ENTRY_DELETE);

        directories.put(key, dir);

        

        return FileVisitResult.CONTINUE;

      }

    });


  }


  public void watchRNDir(Path start) throws IOException, InterruptedException {

    watchService = FileSystems.getDefault().newWatchService();

    registerTree(start);

    while (true) {

      final WatchKey key = watchService.take();

      for (WatchEvent<?> watchEvent : key.pollEvents()) {

        Kind<?> kind = watchEvent.kind();

        WatchEvent<Path> watchEventPath = (WatchEvent<Path>) watchEvent;

        Path filename = watchEventPath.context();

        if (kind == StandardWatchEventKinds.OVERFLOW) {

          continue;

        }

        if (kind == StandardWatchEventKinds.ENTRY_CREATE) {

          final Path directory_path = directories.get(key);

          final Path child = directory_path.resolve(filename);

          if (Files.isDirectory(child, LinkOption.NOFOLLOW_LINKS)) {

            registerTree(child);

          }

        }

        System.out.println(kind + " -> " + filename);

      }

      boolean valid = key.reset();

      if (!valid) {

        directories.remove(key);