    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 */
    017package org.apache.commons.configuration2.io;
    018
    019import java.io.File;
    020import java.net.URL;
    021
    022import org.apache.commons.lang3.StringUtils;
    023import org.apache.commons.lang3.SystemProperties;
    024
    025/**
    026 * <p>
    027 * A specialized implementation of {@code FileLocationStrategy} which searches for files in the user's home directory or
    028 * another special configurable directory.
    029 * </p>
    030 * <p>
    031 * This strategy implementation ignores the URL stored in the passed in {@link FileLocator}. It constructs a file path
    032 * from the configured home directory (which is the user's home directory per default, but can be changed to another
    033 * path), optionally the base path, and the file name. If the resulting path points to an existing file, its URL is
    034 * returned.
    035 * </p>
    036 * <p>
    037 * When constructing an instance it can be configured whether the base path should be taken into account. If this option
    038 * is set, the base path is appended to the home directory if it is not <strong>null</strong>. This is useful for instance to
    039 * select a specific sub directory of the user's home directory. If this option is set to <strong>false</strong>, the base path is
    040 * always ignored, and only the file name is evaluated.
    041 * </p>
    042 */
    043public class HomeDirectoryLocationStrategy implements FileLocationStrategy {
    044
    045    /**
    046     * Obtains the home directory to be used by a new instance. If a directory name is provided, it is used. Otherwise, the
    047     * user's home directory is looked up.
    048     *
    049     * @param homeDir the passed in home directory
    050     * @return the directory to be used
    051     */
    052    private static String fetchHomeDirectory(final String homeDir) {
    053        return homeDir != null ? homeDir : SystemProperties.getUserHome();
    054    }
    055
    056    /** The home directory to be searched for the requested file. */
    057    private final String homeDirectory;
    058
    059    /** The flag whether the base path is to be taken into account. */
    060    private final boolean evaluateBasePath;
    061
    062    /**
    063     * Creates a new instance of {@code HomeDirectoryLocationStrategy} with default settings. The home directory is set to
    064     * the user's home directory. The base path flag is set to <strong>false</strong> (which means that the base path is ignored).
    065     */
    066    public HomeDirectoryLocationStrategy() {
    067        this(false);
    068    }
    069
    070    /**
    071     * Creates a new instance of {@code HomeDirectoryLocationStrategy} and initializes the base path flag. The home
    072     * directory is set to the user's home directory.
    073     *
    074     * @param withBasePath a flag whether the base path should be evaluated
    075     */
    076    public HomeDirectoryLocationStrategy(final boolean withBasePath) {
    077        this(null, withBasePath);
    078    }
    079
    080    /**
    081     * Creates a new instance of {@code HomeDirectoryLocationStrategy} and initializes it with the specified settings.
    082     *
    083     * @param homeDir the path to the home directory (can be <strong>null</strong>)
    084     * @param withBasePath a flag whether the base path should be evaluated
    085     */
    086    public HomeDirectoryLocationStrategy(final String homeDir, final boolean withBasePath) {
    087        homeDirectory = fetchHomeDirectory(homeDir);
    088        evaluateBasePath = withBasePath;
    089    }
    090
    091    /**
    092     * Determines the base path to be used for the current locate() operation.
    093     *
    094     * @param locator the {@code FileLocator}
    095     * @return the base path to be used
    096     */
    097    private String fetchBasePath(final FileLocator locator) {
    098        if (isEvaluateBasePath() && StringUtils.isNotEmpty(locator.getBasePath())) {
    099            return FileLocatorUtils.appendPath(getHomeDirectory(), locator.getBasePath());
    100        }
    101        return getHomeDirectory();
    102    }
    103
    104    /**
    105     * Gets the home directory. In this directory the strategy searches for files.
    106     *
    107     * @return the home directory used by this object
    108     */
    109    public String getHomeDirectory() {
    110        return homeDirectory;
    111    }
    112
    113    /**
    114     * Returns a flag whether the base path is to be taken into account when searching for a file.
    115     *
    116     * @return the flag whether the base path is evaluated
    117     */
    118    public boolean isEvaluateBasePath() {
    119        return evaluateBasePath;
    120    }
    121
    122    /**
    123     * {@inheritDoc} This implementation searches in the home directory for a file described by the passed in
    124     * {@code FileLocator}. If the locator defines a base path and the {@code evaluateBasePath} property is <strong>true</strong>, a
    125     * sub directory of the home directory is searched.
    126     */
    127    @Override
    128    public URL locate(final FileSystem fileSystem, final FileLocator locator) {
    129        if (StringUtils.isNotEmpty(locator.getFileName())) {
    130            final String basePath = fetchBasePath(locator);
    131            final File file = FileLocatorUtils.constructFile(basePath, locator.getFileName());
    132            if (file.isFile()) {
    133                return FileLocatorUtils.convertFileToURL(file);
    134            }
    135        }
    136
    137        return null;
    138    }
    139}