    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;
    023
    024/**
    025 * <p>
    026 * A specialized implementation of {@code FileLocationStrategy} which searches for files in the user's home directory or
    027 * another special configurable directory.
    028 * </p>
    029 * <p>
    030 * This strategy implementation ignores the URL stored in the passed in {@link FileLocator}. It constructs a file path
    031 * from the configured home directory (which is the user's home directory per default, but can be changed to another
    032 * path), optionally the base path, and the file name. If the resulting path points to an existing file, its URL is
    033 * returned.
    034 * </p>
    035 * <p>
    036 * When constructing an instance it can be configured whether the base path should be taken into account. If this option
    037 * is set, the base path is appended to the home directory if it is not <b>null</b>. This is useful for instance to
    038 * select a specific sub directory of the user's home directory. If this option is set to <b>false</b>, the base path is
    039 * always ignored, and only the file name is evaluated.
    040 * </p>
    041 *
    042 */
    043public class HomeDirectoryLocationStrategy implements FileLocationStrategy {
    044    /** Constant for the system property with the user's home directory. */
    045    private static final String PROP_HOME = "user.home";
    046
    047    /** The home directory to be searched for the requested file. */
    048    private final String homeDirectory;
    049
    050    /** The flag whether the base path is to be taken into account. */
    051    private final boolean evaluateBasePath;
    052
    053    /**
    054     * Creates a new instance of {@code HomeDirectoryLocationStrategy} and initializes it with the specified settings.
    055     *
    056     * @param homeDir the path to the home directory (can be <b>null</b>)
    057     * @param withBasePath a flag whether the base path should be evaluated
    058     */
    059    public HomeDirectoryLocationStrategy(final String homeDir, final boolean withBasePath) {
    060        homeDirectory = fetchHomeDirectory(homeDir);
    061        evaluateBasePath = withBasePath;
    062    }
    063
    064    /**
    065     * Creates a new instance of {@code HomeDirectoryLocationStrategy} and initializes the base path flag. The home
    066     * directory is set to the user's home directory.
    067     *
    068     * @param withBasePath a flag whether the base path should be evaluated
    069     */
    070    public HomeDirectoryLocationStrategy(final boolean withBasePath) {
    071        this(null, withBasePath);
    072    }
    073
    074    /**
    075     * Creates a new instance of {@code HomeDirectoryLocationStrategy} with default settings. The home directory is set to
    076     * the user's home directory. The base path flag is set to <b>false</b> (which means that the base path is ignored).
    077     */
    078    public HomeDirectoryLocationStrategy() {
    079        this(false);
    080    }
    081
    082    /**
    083     * Returns the home directory. In this directory the strategy searches for files.
    084     *
    085     * @return the home directory used by this object
    086     */
    087    public String getHomeDirectory() {
    088        return homeDirectory;
    089    }
    090
    091    /**
    092     * Returns a flag whether the base path is to be taken into account when searching for a file.
    093     *
    094     * @return the flag whether the base path is evaluated
    095     */
    096    public boolean isEvaluateBasePath() {
    097        return evaluateBasePath;
    098    }
    099
    100    /**
    101     * {@inheritDoc} This implementation searches in the home directory for a file described by the passed in
    102     * {@code FileLocator}. If the locator defines a base path and the {@code evaluateBasePath} property is <b>true</b>, a
    103     * sub directory of the home directory is searched.
    104     */
    105    @Override
    106    public URL locate(final FileSystem fileSystem, final FileLocator locator) {
    107        if (StringUtils.isNotEmpty(locator.getFileName())) {
    108            final String basePath = fetchBasePath(locator);
    109            final File file = FileLocatorUtils.constructFile(basePath, locator.getFileName());
    110            if (file.isFile()) {
    111                return FileLocatorUtils.convertFileToURL(file);
    112            }
    113        }
    114
    115        return null;
    116    }
    117
    118    /**
    119     * Determines the base path to be used for the current locate() operation.
    120     *
    121     * @param locator the {@code FileLocator}
    122     * @return the base path to be used
    123     */
    124    private String fetchBasePath(final FileLocator locator) {
    125        if (isEvaluateBasePath() && StringUtils.isNotEmpty(locator.getBasePath())) {
    126            return FileLocatorUtils.appendPath(getHomeDirectory(), locator.getBasePath());
    127        }
    128        return getHomeDirectory();
    129    }
    130
    131    /**
    132     * Obtains the home directory to be used by a new instance. If a directory name is provided, it is used. Otherwise, the
    133     * user's home directory is looked up.
    134     *
    135     * @param homeDir the passed in home directory
    136     * @return the directory to be used
    137     */
    138    private static String fetchHomeDirectory(final String homeDir) {
    139        return homeDir != null ? homeDir : System.getProperty(PROP_HOME);
    140    }
    141}