    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 */
    042public class HomeDirectoryLocationStrategy implements FileLocationStrategy {
    043    /** Constant for the system property with the user's home directory. */
    044    private static final String PROP_HOME = "user.home";
    045
    046    /** The home directory to be searched for the requested file. */
    047    private final String homeDirectory;
    048
    049    /** The flag whether the base path is to be taken into account. */
    050    private final boolean evaluateBasePath;
    051
    052    /**
    053     * Creates a new instance of {@code HomeDirectoryLocationStrategy} and initializes it with the specified settings.
    054     *
    055     * @param homeDir the path to the home directory (can be <b>null</b>)
    056     * @param withBasePath a flag whether the base path should be evaluated
    057     */
    058    public HomeDirectoryLocationStrategy(final String homeDir, final boolean withBasePath) {
    059        homeDirectory = fetchHomeDirectory(homeDir);
    060        evaluateBasePath = withBasePath;
    061    }
    062
    063    /**
    064     * Creates a new instance of {@code HomeDirectoryLocationStrategy} and initializes the base path flag. The home
    065     * directory is set to the user's home directory.
    066     *
    067     * @param withBasePath a flag whether the base path should be evaluated
    068     */
    069    public HomeDirectoryLocationStrategy(final boolean withBasePath) {
    070        this(null, withBasePath);
    071    }
    072
    073    /**
    074     * Creates a new instance of {@code HomeDirectoryLocationStrategy} with default settings. The home directory is set to
    075     * the user's home directory. The base path flag is set to <b>false</b> (which means that the base path is ignored).
    076     */
    077    public HomeDirectoryLocationStrategy() {
    078        this(false);
    079    }
    080
    081    /**
    082     * Gets the home directory. In this directory the strategy searches for files.
    083     *
    084     * @return the home directory used by this object
    085     */
    086    public String getHomeDirectory() {
    087        return homeDirectory;
    088    }
    089
    090    /**
    091     * Returns a flag whether the base path is to be taken into account when searching for a file.
    092     *
    093     * @return the flag whether the base path is evaluated
    094     */
    095    public boolean isEvaluateBasePath() {
    096        return evaluateBasePath;
    097    }
    098
    099    /**
    100     * {@inheritDoc} This implementation searches in the home directory for a file described by the passed in
    101     * {@code FileLocator}. If the locator defines a base path and the {@code evaluateBasePath} property is <b>true</b>, a
    102     * sub directory of the home directory is searched.
    103     */
    104    @Override
    105    public URL locate(final FileSystem fileSystem, final FileLocator locator) {
    106        if (StringUtils.isNotEmpty(locator.getFileName())) {
    107            final String basePath = fetchBasePath(locator);
    108            final File file = FileLocatorUtils.constructFile(basePath, locator.getFileName());
    109            if (file.isFile()) {
    110                return FileLocatorUtils.convertFileToURL(file);
    111            }
    112        }
    113
    114        return null;
    115    }
    116
    117    /**
    118     * Determines the base path to be used for the current locate() operation.
    119     *
    120     * @param locator the {@code FileLocator}
    121     * @return the base path to be used
    122     */
    123    private String fetchBasePath(final FileLocator locator) {
    124        if (isEvaluateBasePath() && StringUtils.isNotEmpty(locator.getBasePath())) {
    125            return FileLocatorUtils.appendPath(getHomeDirectory(), locator.getBasePath());
    126        }
    127        return getHomeDirectory();
    128    }
    129
    130    /**
    131     * Obtains the home directory to be used by a new instance. If a directory name is provided, it is used. Otherwise, the
    132     * user's home directory is looked up.
    133     *
    134     * @param homeDir the passed in home directory
    135     * @return the directory to be used
    136     */
    137    private static String fetchHomeDirectory(final String homeDir) {
    138        return homeDir != null ? homeDir : System.getProperty(PROP_HOME);
    139    }
    140}