    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
    033 * href="http://commons.apache.org/vfs/">Commons VFS</a> to determine when a
    034 * file was changed.
    035 * </p>
    036 * <p>
    037 * This reloading strategy is very similar to
    038 * {@link FileHandlerReloadingDetector}, except for the fact that it uses VFS
    039 * and thus can deal with a variety of different configuration sources.
    040 * </p>
    041 * <p>
    042 * This strategy only works with FileConfiguration instances.
    043 * </p>
    044 *
    045 * @author <a
    046 *         href="http://commons.apache.org/configuration/team-list.html">Commons
    047 *         Configuration team</a>
    048 * @since 1.7
    049 */
    050public class VFSFileHandlerReloadingDetector extends FileHandlerReloadingDetector
    051{
    052    /** Stores the logger.*/
    053    private final Log log = LogFactory.getLog(getClass());
    054
    055    /**
    056     * Creates a new instance of {@code VFSFileHandlerReloadingDetector} and
    057     * initializes it with an empty {@code FileHandler} object.
    058     */
    059    public VFSFileHandlerReloadingDetector()
    060    {
    061        super();
    062    }
    063
    064    /**
    065     * Creates a new instance of {@code VFSFileHandlerReloadingDetector} and
    066     * initializes it with the given {@code FileHandler} object and the given
    067     * refresh delay.
    068     *
    069     * @param handler the {@code FileHandler}
    070     * @param refreshDelay the refresh delay
    071     */
    072    public VFSFileHandlerReloadingDetector(final FileHandler handler,
    073            final long refreshDelay)
    074    {
    075        super(handler, refreshDelay);
    076    }
    077
    078    /**
    079     * Creates a new instance of {@code VFSFileHandlerReloadingDetector} and
    080     * initializes it with the given {@code FileHandler} object.
    081     *
    082     * @param handler the {@code FileHandler}
    083     */
    084    public VFSFileHandlerReloadingDetector(final FileHandler handler)
    085    {
    086        super(handler);
    087    }
    088
    089    /**
    090     * {@inheritDoc} This implementation uses Commons VFS to obtain a
    091     * {@code FileObject} and read the date of the last modification.
    092     */
    093    @Override
    094    protected long getLastModificationDate()
    095    {
    096        final FileObject file = getFileObject();
    097        try
    098        {
    099            if (file == null || !file.exists())
    100            {
    101                return 0;
    102            }
    103
    104            return file.getContent().getLastModifiedTime();
    105        }
    106        catch (final FileSystemException ex)
    107        {
    108            log.error("Unable to get last modified time for"
    109                    + file.getName().getURI(), ex);
    110            return 0;
    111        }
    112    }
    113
    114    /**
    115     * Returns the file that is monitored by this strategy. Note that the return
    116     * value can be <b>null </b> under some circumstances.
    117     *
    118     * @return the monitored file
    119     */
    120    protected FileObject getFileObject()
    121    {
    122        if (!getFileHandler().isLocationDefined())
    123        {
    124            return null;
    125        }
    126
    127        try
    128        {
    129            final FileSystemManager fsManager = VFS.getManager();
    130            final String uri = resolveFileURI();
    131            if (uri == null)
    132            {
    133                throw new ConfigurationRuntimeException("Unable to determine file to monitor");
    134            }
    135            return fsManager.resolveFile(uri);
    136        }
    137        catch (final FileSystemException fse)
    138        {
    139            final String msg = "Unable to monitor " + getFileHandler().getURL().toString();
    140            log.error(msg);
    141            throw new ConfigurationRuntimeException(msg, fse);
    142        }
    143    }
    144
    145    /**
    146     * Resolves the URI of the monitored file.
    147     *
    148     * @return the URI of the monitored file or <b>null</b> if it cannot be
    149     *         resolved
    150     */
    151    protected String resolveFileURI()
    152    {
    153        final FileSystem fs = getFileHandler().getFileSystem();
    154        final String uri =
    155                fs.getPath(null, getFileHandler().getURL(), getFileHandler()
    156                        .getBasePath(), getFileHandler().getFileName());
    157        return uri;
    158    }
    159}