DirectoryWatcherExample.java

package io.arleigh.reporting;

import java.io.IOException;
import java.io.InputStream;
import java.nio.file.FileSystems;
import java.nio.file.Files;
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;


public class DirectoryWatcherExample {

  private static void printContents(Path path) {

    //using NIO.2 unbuffered stream
    int n;
    try (InputStream in = Files.newInputStream(path)) {
      while ((n = in.read()) != -1) {
        System.out.print((char) n);
      }
    } catch (IOException e) {
      System.err.println(e);
    }

  }

  public static void main(String[] args) {
    try {
      WatchService watchService = FileSystems.getDefault().newWatchService();

      String home = System.getProperty("user.home");

      System.out.println(home);

      Path path = Paths.get(home);

      path.register(
          watchService,
          StandardWatchEventKinds.ENTRY_CREATE,
          StandardWatchEventKinds.ENTRY_DELETE,
          StandardWatchEventKinds.ENTRY_MODIFY);

      WatchKey key;
      while ((key = watchService.take()) != null) {
        Path dir = (Path) key.watchable();
        for (WatchEvent<?> event : key.pollEvents()) {
          System.out.println(
              "Event kind:" + event.kind()
                  + ". File affected: " + event.context() + ".");
          // Path fullPath = dir.resolve(((WatchEvent<Path>) event).context());
          // printContents(fullPath);
        }
        key.reset();
      }
    } catch (Exception e) {
      System.exit(1);
    }
  }
}