Uses the Java 7 WatchEvent filesystem API from within Scala

dirwatcher.scala

/**
 * watcher.scala
 *
 * Uses the Java 7 WatchEvent filesystem API from within Scala.
 * Based on http://markusjais.com/file-system-events-with-java-7/
 * 
 * @author Chris Eberle <[email protected]>
 * @version 0.1 
 */

import scala.collection.JavaConverters._
import util.control.Breaks._
import java.io.IOException
import java.nio.file.Path
import java.nio.file.StandardWatchEventKinds
import java.nio.file.WatchEvent
import java.nio.file.WatchKey
import java.nio.file.WatchService
import java.nio.file.FileSystems

class DirectoryWatcher(val path:Path) extends Runnable {

  def printEvent(event:WatchEvent[_]) : Unit = {
    val kind = event.kind
    val event_path = event.context().asInstanceOf[Path]
    if(kind.equals(StandardWatchEventKinds.ENTRY_CREATE)) {
      println("Entry created: " + event_path)
    }
    else if(kind.equals(StandardWatchEventKinds.ENTRY_DELETE)) {
      println("Entry deleted: " + event_path)
    }
    else if(kind.equals(StandardWatchEventKinds.ENTRY_MODIFY)) {
      println("Entry modified: " + event_path)
    }
  }

  override def run(): Unit = {
    try {
      val watchService = path.getFileSystem().newWatchService()
      path.register(watchService, StandardWatchEventKinds.ENTRY_CREATE,
                    StandardWatchEventKinds.ENTRY_MODIFY,
                    StandardWatchEventKinds.ENTRY_DELETE)
      breakable {
        while (true) {
          val watchKey = watchService.take()
          watchKey.pollEvents().asScala.foreach( e => {
            printEvent(e)
          })
          if (!watchKey.reset()) {
            println("No longer valid")
            watchKey.cancel()
            watchService.close()
            break
          }
        }
      }
    } catch {
      case ie: InterruptedException => println("InterruptedException: " + ie)
      case ioe: IOException => println("IOException: " + ioe)
      case e: Exception => println("Exception: " + e)
    }
  }
}

println("Starting watch service...")
val path = FileSystems.getDefault().getPath("/home/chris/scala/watch")
val dir_watcher = new DirectoryWatcher(path)
val watch_thread = new Thread(dir_watcher)
watch_thread.start()