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