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.convert; 018 019import java.lang.reflect.Array; 020import java.util.ArrayList; 021import java.util.Collection; 022import java.util.Iterator; 023import java.util.LinkedList; 024 025/** 026 * <p> 027 * An abstract base class for concrete {@code ListDelimiterHandler} 028 * implementations. 029 * </p> 030 * <p> 031 * This base class provides a fully functional implementation for parsing a 032 * value object which can deal with different cases like collections, arrays, 033 * iterators, etc. This logic is typically needed by every concrete subclass. 034 * Other methods are partly implemented handling special corner cases like 035 * <b>null</b> values; concrete subclasses do not have do implement the 036 * corresponding checks. 037 * </p> 038 * 039 * @since 2.0 040 */ 041public abstract class AbstractListDelimiterHandler implements 042 ListDelimiterHandler 043{ 044 /** 045 * {@inheritDoc} Depending on the type of the passed in object the following 046 * things happen: 047 * <ul> 048 * <li>Strings are checked for delimiter characters and split if necessary. 049 * This is done by calling the {@code split()} method.</li> 050 * <li>For objects implementing the {@code Iterable} interface, the 051 * corresponding {@code Iterator} is obtained, and contained elements are 052 * added to the resulting iteration.</li> 053 * <li>Arrays are treated as {@code Iterable} objects.</li> 054 * <li>All other types are directly inserted.</li> 055 * <li>Recursive combinations are supported, e.g. a collection containing an 056 * array that contains strings: The resulting collection will only contain 057 * primitive objects.</li> 058 * </ul> 059 */ 060 @Override 061 public Iterable<?> parse(final Object value) 062 { 063 return flatten(value); 064 } 065 066 /** 067 * {@inheritDoc} This implementation handles the case that the passed in 068 * string is <b>null</b>. In this case, an empty collection is returned. 069 * Otherwise, this method delegates to {@link #splitString(String, boolean)}. 070 */ 071 @Override 072 public Collection<String> split(final String s, final boolean trim) 073 { 074 if (s == null) 075 { 076 return new ArrayList<>(0); 077 } 078 return splitString(s, trim); 079 } 080 081 /** 082 * {@inheritDoc} This implementation checks whether the object to be escaped 083 * is a string. If yes, it delegates to {@link #escapeString(String)}, 084 * otherwise no escaping is performed. Eventually, the passed in transformer 085 * is invoked so that additional encoding can be performed. 086 */ 087 @Override 088 public Object escape(final Object value, final ValueTransformer transformer) 089 { 090 final Object escValue = 091 value instanceof String ? escapeString((String) value) 092 : value; 093 return transformer.transformValue(escValue); 094 } 095 096 /** 097 * Actually splits the passed in string which is guaranteed to be not 098 * <b>null</b>. This method is called by the base implementation of the 099 * {@code split()} method. Here the actual splitting logic has to be 100 * implemented. 101 * 102 * @param s the string to be split (not <b>null</b>) 103 * @param trim a flag whether the single components have to be trimmed 104 * @return a collection with the extracted components of the passed in 105 * string 106 */ 107 protected abstract Collection<String> splitString(String s, boolean trim); 108 109 /** 110 * Escapes the specified string. This method is called by {@code escape()} 111 * if the passed in object is a string. Concrete subclasses have to 112 * implement their specific escaping logic here, so that the list delimiters 113 * they support are properly escaped. 114 * 115 * @param s the string to be escaped (not <b>null</b>) 116 * @return the escaped string 117 */ 118 protected abstract String escapeString(String s); 119 120 /** 121 * Extracts all values contained in the specified object up to the given 122 * limit. The passed in object is evaluated (if necessary in a recursive 123 * way). If it is a complex object (e.g. a collection or an array), all its 124 * elements are processed recursively and added to a target collection. The 125 * process stops if the limit is reached, but depending on the input object, 126 * it might be exceeded. (The limit is just an indicator to stop the process 127 * to avoid unnecessary work if the caller is only interested in a few 128 * values.) 129 * 130 * @param value the value to be processed 131 * @param limit the limit for aborting the processing 132 * @return a "flat" collection containing all primitive values of 133 * the passed in object 134 */ 135 Collection<?> flatten(final Object value, final int limit) 136 { 137 if (value instanceof String) 138 { 139 return split((String) value, true); 140 } 141 142 final Collection<Object> result = new LinkedList<>(); 143 if (value instanceof Iterable) 144 { 145 flattenIterator(result, ((Iterable<?>) value).iterator(), limit); 146 } 147 else if (value instanceof Iterator) 148 { 149 flattenIterator(result, (Iterator<?>) value, limit); 150 } 151 else if (value != null) 152 { 153 if (value.getClass().isArray()) 154 { 155 for (int len = Array.getLength(value), idx = 0, size = 0; idx < len 156 && size < limit; idx++, size = result.size()) 157 { 158 result.addAll(flatten(Array.get(value, idx), limit - size)); 159 } 160 } 161 else 162 { 163 result.add(value); 164 } 165 } 166 167 return result; 168 } 169 170 /** 171 * Performs the actual work as advertised by the {@code parse()} method. 172 * This method delegates to {@link #flatten(Object, int)} without specifying 173 * a limit. 174 * 175 * @param value the value to be processed 176 * @return a "flat" collection containing all primitive values of 177 * the passed in object 178 */ 179 private Collection<?> flatten(final Object value) 180 { 181 return flatten(value, Integer.MAX_VALUE); 182 } 183 184 /** 185 * Flattens the given iterator. For each element in the iteration 186 * {@code flatten()} is called recursively. 187 * 188 * @param target the target collection 189 * @param it the iterator to process 190 * @param limit a limit for the number of elements to extract 191 */ 192 private void flattenIterator(final Collection<Object> target, final Iterator<?> it, final int limit) 193 { 194 int size = target.size(); 195 while (size < limit && it.hasNext()) 196 { 197 target.addAll(flatten(it.next(), limit - size)); 198 size = target.size(); 199 } 200 } 201}