| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License |
| */ |
| |
| package org.apache.storm.daemon.common; |
| |
| import static java.nio.file.StandardWatchEventKinds.ENTRY_MODIFY; |
| |
| import java.io.IOException; |
| import java.nio.file.Path; |
| import java.nio.file.WatchEvent; |
| import java.nio.file.WatchKey; |
| import java.nio.file.WatchService; |
| import java.util.Collections; |
| import java.util.List; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| public class FileWatcher implements Runnable { |
| |
| private static final Logger LOG = LoggerFactory.getLogger(FileWatcher.class); |
| |
| private final WatchService watcher; |
| private volatile boolean stopped = false; |
| private final Path watchedFile; |
| private final Callback callback; |
| List<WatchEvent.Kind<Path>> kinds; |
| |
| public FileWatcher(final Path watchedFile, Callback callback) throws IOException { |
| this(watchedFile, callback, Collections.singletonList(ENTRY_MODIFY)); |
| } |
| |
| public FileWatcher(final Path watchedFile, Callback callback, List<WatchEvent.Kind<Path>> kinds) throws IOException { |
| this.watchedFile = watchedFile; |
| this.callback = callback; |
| Path parent = watchedFile.getParent(); |
| this.watcher = parent.getFileSystem().newWatchService(); |
| this.kinds = kinds; |
| parent.register(watcher, this.kinds.toArray(new WatchEvent.Kind[0])); |
| } |
| |
| public void start() { |
| Thread t = new Thread(this, "FileWatcher-" + watchedFile.getFileName()); |
| t.setDaemon(true); |
| LOG.info("Starting FileWatcher on {}", watchedFile); |
| t.start(); |
| } |
| |
| public void stop() { |
| LOG.info("Stopping FileWatcher on {}", watchedFile); |
| this.stopped = true; |
| } |
| |
| @Override |
| public void run() { |
| while (!stopped) { |
| WatchKey watchKey; |
| try { |
| watchKey = watcher.take(); |
| } catch (InterruptedException ex) { |
| LOG.warn("FileWatch for {} is interrupted", watchedFile, ex); |
| Thread.currentThread().interrupt(); |
| return; |
| } |
| for (WatchEvent<?> event : watchKey.pollEvents()) { |
| if (this.kinds.contains(event.kind()) && event.context().equals(watchedFile.getFileName())) { |
| try { |
| LOG.info("Event {} on {}; invoking callback", event.kind(), watchedFile); |
| callback.run(); |
| } catch (Exception ex) { |
| LOG.error("Error invoking FileWatcher callback for {}", watchedFile, ex); |
| } |
| } |
| } |
| watchKey.reset(); |
| } |
| } |
| |
| public interface Callback { |
| void run() throws Exception; |
| } |
| } |