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