| /* |
| * 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.commons.vfs2.util; |
| |
| import java.lang.ref.WeakReference; |
| |
| import org.apache.commons.vfs2.FileChangeEvent; |
| import org.apache.commons.vfs2.FileListener; |
| import org.apache.commons.vfs2.FileName; |
| import org.apache.commons.vfs2.FileObject; |
| import org.apache.commons.vfs2.FileSystem; |
| |
| /** |
| * Wrap a listener with a WeakReference. |
| * |
| * @since 2.0 |
| */ |
| public class WeakRefFileListener implements FileListener |
| { |
| private final FileSystem fs; |
| private final FileName name; |
| private final WeakReference<FileListener> listener; |
| |
| protected WeakRefFileListener(final FileObject file, final FileListener listener) |
| { |
| this.fs = file.getFileSystem(); |
| this.name = file.getName(); |
| this.listener = new WeakReference<FileListener>(listener); |
| } |
| |
| /** |
| * This will install the {@code listener} at the given {@code file}. |
| * @param file The FileObject to listen on. |
| * @param listener The FileListener |
| */ |
| public static void installListener(final FileObject file, final FileListener listener) |
| { |
| final WeakRefFileListener weakListener = new WeakRefFileListener(file, listener); |
| |
| file.getFileSystem().addListener(file, new WeakRefFileListener(file, weakListener)); |
| } |
| |
| /** |
| * returns the wrapped listener. If it is gone, the WeakRefFileListener wrapper will |
| * remove itself from the list of listeners. |
| * @return The FileListener. |
| * @throws Exception if an error occurs. |
| */ |
| protected FileListener getListener() throws Exception |
| { |
| final FileListener listener = this.listener.get(); |
| if (listener == null) |
| { |
| final FileObject file = fs.resolveFile(name); |
| file.getFileSystem().removeListener(file, this); |
| } |
| return listener; |
| } |
| |
| /** |
| * Called when a file is created. |
| * @param event The FileChangeEvent. |
| * @throws Exception if an error occurs. |
| */ |
| @Override |
| public void fileCreated(final FileChangeEvent event) throws Exception |
| { |
| final FileListener listener = getListener(); |
| if (listener == null) |
| { |
| return; |
| } |
| listener.fileCreated(event); |
| } |
| |
| /** |
| * Called when a file is deleted. |
| * @param event The FileChangeEvent. |
| * @throws Exception if an error occurs. |
| */ |
| @Override |
| public void fileDeleted(final FileChangeEvent event) throws Exception |
| { |
| final FileListener listener = getListener(); |
| if (listener == null) |
| { |
| return; |
| } |
| listener.fileDeleted(event); |
| } |
| |
| /** |
| * Called when a file is changed. |
| * <p> |
| * This will only happen if you monitor the file using {@link org.apache.commons.vfs2.FileMonitor}. |
| * |
| * @param event The FileChangeEvent. |
| * @throws Exception if an error occurs. |
| */ |
| @Override |
| public void fileChanged(final FileChangeEvent event) throws Exception |
| { |
| final FileListener listener = getListener(); |
| if (listener == null) |
| { |
| return; |
| } |
| listener.fileChanged(event); |
| } |
| } |