001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *     http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.configuration2.reloading;
019
020import org.apache.commons.configuration2.ex.ConfigurationRuntimeException;
021import org.apache.commons.configuration2.io.FileHandler;
022import org.apache.commons.configuration2.io.FileSystem;
023import org.apache.commons.logging.Log;
024import org.apache.commons.logging.LogFactory;
025import org.apache.commons.vfs2.FileObject;
026import org.apache.commons.vfs2.FileSystemException;
027import org.apache.commons.vfs2.FileSystemManager;
028import org.apache.commons.vfs2.VFS;
029
030/**
031 * <p>
032 * A file-based reloading strategy that uses <a href="https://commons.apache.org/vfs/">Commons VFS</a> to determine when
033 * a file was changed.
034 * </p>
035 * <p>
036 * This reloading strategy is very similar to {@link FileHandlerReloadingDetector}, except for the fact that it uses VFS
037 * and thus can deal with a variety of different configuration sources.
038 * </p>
039 * <p>
040 * This strategy only works with FileConfiguration instances.
041 * </p>
042 *
043 * @since 1.7
044 */
045public class VFSFileHandlerReloadingDetector extends FileHandlerReloadingDetector {
046    /** Stores the logger. */
047    private final Log log = LogFactory.getLog(getClass());
048
049    /**
050     * Creates a new instance of {@code VFSFileHandlerReloadingDetector} and initializes it with an empty
051     * {@code FileHandler} object.
052     */
053    public VFSFileHandlerReloadingDetector() {
054    }
055
056    /**
057     * Creates a new instance of {@code VFSFileHandlerReloadingDetector} and initializes it with the given
058     * {@code FileHandler} object and the given refresh delay.
059     *
060     * @param handler the {@code FileHandler}
061     * @param refreshDelay the refresh delay
062     */
063    public VFSFileHandlerReloadingDetector(final FileHandler handler, final long refreshDelay) {
064        super(handler, refreshDelay);
065    }
066
067    /**
068     * Creates a new instance of {@code VFSFileHandlerReloadingDetector} and initializes it with the given
069     * {@code FileHandler} object.
070     *
071     * @param handler the {@code FileHandler}
072     */
073    public VFSFileHandlerReloadingDetector(final FileHandler handler) {
074        super(handler);
075    }
076
077    /**
078     * {@inheritDoc} This implementation uses Commons VFS to obtain a {@code FileObject} and read the date of the last
079     * modification.
080     */
081    @Override
082    protected long getLastModificationDate() {
083        final FileObject file = getFileObject();
084        try {
085            if (file == null || !file.exists()) {
086                return 0;
087            }
088
089            return file.getContent().getLastModifiedTime();
090        } catch (final FileSystemException ex) {
091            log.error("Unable to get last modified time for" + file.getName().getURI(), ex);
092            return 0;
093        }
094    }
095
096    /**
097     * Gets the file that is monitored by this strategy. Note that the return value can be <b>null </b> under some
098     * circumstances.
099     *
100     * @return the monitored file
101     */
102    protected FileObject getFileObject() {
103        if (!getFileHandler().isLocationDefined()) {
104            return null;
105        }
106
107        try {
108            final FileSystemManager fsManager = VFS.getManager();
109            final String uri = resolveFileURI();
110            if (uri == null) {
111                throw new ConfigurationRuntimeException("Unable to determine file to monitor");
112            }
113            return fsManager.resolveFile(uri);
114        } catch (final FileSystemException fse) {
115            final String msg = "Unable to monitor " + getFileHandler().getURL().toString();
116            log.error(msg);
117            throw new ConfigurationRuntimeException(msg, fse);
118        }
119    }
120
121    /**
122     * Resolves the URI of the monitored file.
123     *
124     * @return the URI of the monitored file or <b>null</b> if it cannot be resolved
125     */
126    protected String resolveFileURI() {
127        final FileSystem fs = getFileHandler().getFileSystem();
128        return fs.getPath(null, getFileHandler().getURL(), getFileHandler().getBasePath(), getFileHandler().getFileName());
129    }
130}