    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
    027 * for files in the user's home directory or another special configurable
    028 * directory.
    029 * </p>
    030 * <p>
    031 * This strategy implementation ignores the URL stored in the passed in
    032 * {@link FileLocator}. It constructs a file path from the configured home
    033 * directory (which is the user's home directory per default, but can be changed
    034 * to another path), optionally the base path, and the file name. If the
    035 * resulting path points to an existing file, its URL is returned.
    036 * </p>
    037 * <p>
    038 * When constructing an instance it can be configured whether the base path
    039 * should be taken into account. If this option is set, the base path is
    040 * appended to the home directory if it is not <b>null</b>. This is useful for
    041 * instance to select a specific sub directory of the user's home directory. If
    042 * this option is set to <b>false</b>, the base path is always ignored, and only
    043 * the file name is evaluated.
    044 * </p>
    045 *
    046 */
    047public class HomeDirectoryLocationStrategy implements FileLocationStrategy
    048{
    049    /** Constant for the system property with the user's home directory. */
    050    private static final String PROP_HOME = "user.home";
    051
    052    /** The home directory to be searched for the requested file. */
    053    private final String homeDirectory;
    054
    055    /** The flag whether the base path is to be taken into account. */
    056    private final boolean evaluateBasePath;
    057
    058    /**
    059     * Creates a new instance of {@code HomeDirectoryLocationStrategy} and
    060     * initializes it with the specified settings.
    061     *
    062     * @param homeDir the path to the home directory (can be <b>null</b>)
    063     * @param withBasePath a flag whether the base path should be evaluated
    064     */
    065    public HomeDirectoryLocationStrategy(final String homeDir, final boolean withBasePath)
    066    {
    067        homeDirectory = fetchHomeDirectory(homeDir);
    068        evaluateBasePath = withBasePath;
    069    }
    070
    071    /**
    072     * Creates a new instance of {@code HomeDirectoryLocationStrategy} and
    073     * initializes the base path flag. The home directory is set to the user's
    074     * home directory.
    075     *
    076     * @param withBasePath a flag whether the base path should be evaluated
    077     */
    078    public HomeDirectoryLocationStrategy(final boolean withBasePath)
    079    {
    080        this(null, withBasePath);
    081    }
    082
    083    /**
    084     * Creates a new instance of {@code HomeDirectoryLocationStrategy} with
    085     * default settings. The home directory is set to the user's home directory.
    086     * The base path flag is set to <b>false</b> (which means that the base path
    087     * is ignored).
    088     */
    089    public HomeDirectoryLocationStrategy()
    090    {
    091        this(false);
    092    }
    093
    094    /**
    095     * Returns the home directory. In this directory the strategy searches for
    096     * files.
    097     *
    098     * @return the home directory used by this object
    099     */
    100    public String getHomeDirectory()
    101    {
    102        return homeDirectory;
    103    }
    104
    105    /**
    106     * Returns a flag whether the base path is to be taken into account when
    107     * searching for a file.
    108     *
    109     * @return the flag whether the base path is evaluated
    110     */
    111    public boolean isEvaluateBasePath()
    112    {
    113        return evaluateBasePath;
    114    }
    115
    116    /**
    117     * {@inheritDoc} This implementation searches in the home directory for a
    118     * file described by the passed in {@code FileLocator}. If the locator
    119     * defines a base path and the {@code evaluateBasePath} property is
    120     * <b>true</b>, a sub directory of the home directory is searched.
    121     */
    122    @Override
    123    public URL locate(final FileSystem fileSystem, final FileLocator locator)
    124    {
    125        if (StringUtils.isNotEmpty(locator.getFileName()))
    126        {
    127            final String basePath = fetchBasePath(locator);
    128            final File file =
    129                    FileLocatorUtils.constructFile(basePath,
    130                            locator.getFileName());
    131            if (file.isFile())
    132            {
    133                return FileLocatorUtils.convertFileToURL(file);
    134            }
    135        }
    136
    137        return null;
    138    }
    139
    140    /**
    141     * Determines the base path to be used for the current locate() operation.
    142     *
    143     * @param locator the {@code FileLocator}
    144     * @return the base path to be used
    145     */
    146    private String fetchBasePath(final FileLocator locator)
    147    {
    148        if (isEvaluateBasePath()
    149                && StringUtils.isNotEmpty(locator.getBasePath()))
    150        {
    151            return FileLocatorUtils.appendPath(getHomeDirectory(),
    152                    locator.getBasePath());
    153        }
    154        return getHomeDirectory();
    155    }
    156
    157    /**
    158     * Obtains the home directory to be used by a new instance. If a directory
    159     * name is provided, it is used. Otherwise, the user's home directory is
    160     * looked up.
    161     *
    162     * @param homeDir the passed in home directory
    163     * @return the directory to be used
    164     */
    165    private static String fetchHomeDirectory(final String homeDir)
    166    {
    167        return homeDir != null ? homeDir : System.getProperty(PROP_HOME);
    168    }
    169}