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}