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 *     https://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
047    /** Stores the logger. */
048    private final Log log = LogFactory.getLog(getClass());
049
050    /**
051     * Creates a new instance of {@code VFSFileHandlerReloadingDetector} and initializes it with an empty
052     * {@code FileHandler} object.
053     */
054    public VFSFileHandlerReloadingDetector() {
055    }
056
057    /**
058     * Creates a new instance of {@code VFSFileHandlerReloadingDetector} and initializes it with the given
059     * {@code FileHandler} object.
060     *
061     * @param handler the {@code FileHandler}
062     */
063    public VFSFileHandlerReloadingDetector(final FileHandler handler) {
064        super(handler);
065    }
066
067    /**
068     * Creates a new instance of {@code VFSFileHandlerReloadingDetector} and initializes it with the given
069     * {@code FileHandler} object and the given refresh delay.
070     *
071     * @param handler the {@code FileHandler}
072     * @param refreshDelay the refresh delay
073     */
074    public VFSFileHandlerReloadingDetector(final FileHandler handler, final long refreshDelay) {
075        super(handler, refreshDelay);
076    }
077
078    /**
079     * Gets the file that is monitored by this strategy. Note that the return value can be <strong>null </strong> under some
080     * circumstances.
081     *
082     * @return the monitored file
083     */
084    protected FileObject getFileObject() {
085        if (!getFileHandler().isLocationDefined()) {
086            return null;
087        }
088
089        try {
090            final FileSystemManager fsManager = VFS.getManager();
091            final String uri = resolveFileURI();
092            if (uri == null) {
093                throw new ConfigurationRuntimeException("Unable to determine file to monitor");
094            }
095            return fsManager.resolveFile(uri);
096        } catch (final FileSystemException e) {
097            final String msg = "Unable to monitor " + getFileHandler().getURL().toString();
098            log.error(msg);
099            throw new ConfigurationRuntimeException(msg, e);
100        }
101    }
102
103    /**
104     * {@inheritDoc} This implementation uses Commons VFS to obtain a {@code FileObject} and read the date of the last
105     * modification.
106     */
107    @Override
108    protected long getLastModificationDate() {
109        final FileObject file = getFileObject();
110        try {
111            if (file == null || !file.exists()) {
112                return 0;
113            }
114
115            return file.getContent().getLastModifiedTime();
116        } catch (final FileSystemException ex) {
117            log.error("Unable to get last modified time for" + file.getName().getURI(), ex);
118            return 0;
119        }
120    }
121
122    /**
123     * Resolves the URI of the monitored file.
124     *
125     * @return the URI of the monitored file or <strong>null</strong> if it cannot be resolved
126     */
127    protected String resolveFileURI() {
128        final FileSystem fs = getFileHandler().getFileSystem();
129        return fs.getPath(null, getFileHandler().getURL(), getFileHandler().getBasePath(), getFileHandler().getFileName());
130    }
131}