Watching a Directory Tree - Java File Path IO

Java examples for File Path IO:File Watcher

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Description

Watching a Directory Tree

Demo Code

import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
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 {

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

      @Override/*from  ww w . j  a va  2  s . c om*/
      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);
        if (directories.isEmpty()) {
          break;
        }
      }
    }
    watchService.close();
  }
}
public class Main {
  public static void main(String[] args) {
    Path path = Paths.get("C:/folder1");
    WatchRecursive watch = new WatchRecursive();
    try {
      watch.watchRNDir(path);
    } catch (IOException | InterruptedException ex) {
      System.err.println(ex);
    }
  }
}

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