    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.builder.combined;
    018
    019import java.util.Collection;
    020
    021import org.apache.commons.configuration2.builder.BuilderParameters;
    022import org.apache.commons.configuration2.builder.FileBasedBuilderParametersImpl;
    023import org.apache.commons.configuration2.ex.ConfigurationException;
    024
    025/**
    026 * <p>
    027 * A specialized implementation of {@link ConfigurationBuilderProvider} which
    028 * determines the name of the result configuration class based on the extension
    029 * of the file to load.
    030 * </p>
    031 * <p>
    032 * This class works analogously to its base class {@link BaseConfigurationBuilderProvider};
    033 * especially, the resulting builder is created based on reflection. It extends
    034 * the super class's functionality by a specific mechanism for determining the
    035 * resulting configuration class: At construction time two configuration class
    036 * names and a file extension are passed in. If a file name is provided in the
    037 * builder's initialization parameters and this file name has the specified
    038 * extension, then the first configuration class name is used; otherwise the
    039 * default configuration class name is selected.
    040 * </p>
    041 * <p>
    042 * There are some tags for {@code CombinedConfigurationProvider} which can
    043 * produce different results depending on the configuration files they have to
    044 * load. This class can be used to implement this feature in a generic way.
    045 * </p>
    046 *
    047 * @since 2.0
    048 */
    049public class FileExtensionConfigurationBuilderProvider extends
    050        BaseConfigurationBuilderProvider
    051{
    052    /** Constant for the file extension separator. */
    053    private static final char EXT_SEPARATOR = '.';
    054
    055    /** The matching configuration class. */
    056    private final String matchingConfigurationClass;
    057
    058    /** The file extension. */
    059    private final String extension;
    060
    061    /**
    062     * Creates a new instance of
    063     * {@code FileExtensionConfigurationBuilderProvider}.
    064     *
    065     * @param bldrCls the name of the builder class
    066     * @param reloadBldrCls the name of a builder class to be used if reloading
    067     *        support is required (<b>null</b> if reloading is not supported)
    068     * @param matchingConfigCls the name of the configuration class to be used
    069     *        if the provided file extension matches (must not be <b>null</b>)
    070     * @param defConfigClass the name of the configuration class to be used if
    071     *        the provided file extension does not match (must not be
    072     *        <b>null</b>)
    073     * @param ext the file extension to select the configuration class (must not
    074     *        be <b>null</b>)
    075     * @param paramCls a collection with the names of parameters classes; an
    076     *        instance of a parameters object with basic properties is created
    077     *        automatically and does not need to be contained in this list; the
    078     *        collection can be <b>null</b> if no additional parameter objects
    079     *        are needed
    080     * @throws IllegalArgumentException if a required parameter is missing
    081     */
    082    public FileExtensionConfigurationBuilderProvider(final String bldrCls,
    083            final String reloadBldrCls, final String matchingConfigCls,
    084            final String defConfigClass, final String ext, final Collection<String> paramCls)
    085    {
    086        super(bldrCls, reloadBldrCls, defConfigClass, paramCls);
    087        if (matchingConfigCls == null)
    088        {
    089            throw new IllegalArgumentException(
    090                    "Matching configuration class must not be null!");
    091        }
    092        if (ext == null)
    093        {
    094            throw new IllegalArgumentException(
    095                    "File extension must not be null!");
    096        }
    097
    098        matchingConfigurationClass = matchingConfigCls;
    099        extension = ext;
    100    }
    101
    102    /**
    103     * Returns the name of the matching configuration class. This class is used
    104     * if the file extension matches the extension of this provider.
    105     *
    106     * @return the matching configuration class
    107     */
    108    public String getMatchingConfigurationClass()
    109    {
    110        return matchingConfigurationClass;
    111    }
    112
    113    /**
    114     * Returns the file extension of this provider.
    115     *
    116     * @return the file extension to match
    117     */
    118    public String getExtension()
    119    {
    120        return extension;
    121    }
    122
    123    /**
    124     * {@inheritDoc} This implementation tries to find a
    125     * {@link FileBasedBuilderParametersImpl} object in the parameter objects. If
    126     * one is found, the extension of the file name is obtained and compared
    127     * against the stored file extension. In case of a match, the matching
    128     * configuration class is selected, otherwise the default one.
    129     */
    130    @Override
    131    protected String determineConfigurationClass(final ConfigurationDeclaration decl,
    132            final Collection<BuilderParameters> params) throws ConfigurationException
    133    {
    134        final String currentExt = extractExtension(fetchCurrentFileName(params));
    135        return getExtension().equalsIgnoreCase(currentExt) ? getMatchingConfigurationClass()
    136                : getConfigurationClass();
    137    }
    138
    139    /**
    140     * Tries to obtain the current file name from the given list of parameter
    141     * objects.
    142     *
    143     * @param params the parameter objects
    144     * @return the file name or <b>null</b> if unspecified
    145     */
    146    private static String fetchCurrentFileName(
    147            final Collection<BuilderParameters> params)
    148    {
    149        for (final BuilderParameters p : params)
    150        {
    151            if (p instanceof FileBasedBuilderParametersImpl)
    152            {
    153                final FileBasedBuilderParametersImpl fp = (FileBasedBuilderParametersImpl) p;
    154                return fp.getFileHandler().getFileName();
    155            }
    156        }
    157        return null;
    158    }
    159
    160    /**
    161     * Extracts the extension from the given file name. The name can be
    162     * <b>null</b>.
    163     *
    164     * @param fileName the file name
    165     * @return the extension (<b>null</b> if there is none)
    166     */
    167    private static String extractExtension(final String fileName)
    168    {
    169        if (fileName == null)
    170        {
    171            return null;
    172        }
    173
    174        final int pos = fileName.lastIndexOf(EXT_SEPARATOR);
    175        return (pos < 0) ? null : fileName.substring(pos + 1);
    176    }
    177}