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 * @version $Id: AbstractListDelimiterHandler.java 1842194 2018-09-27 22:24:23Z ggregory $ 040 * @since 2.0 041 */ 042public abstract class AbstractListDelimiterHandler implements 043 ListDelimiterHandler 044{ 045 /** 046 * {@inheritDoc} Depending on the type of the passed in object the following 047 * things happen: 048 * <ul> 049 * <li>Strings are checked for delimiter characters and split if necessary. 050 * This is done by calling the {@code split()} method.</li> 051 * <li>For objects implementing the {@code Iterable} interface, the 052 * corresponding {@code Iterator} is obtained, and contained elements are 053 * added to the resulting iteration.</li> 054 * <li>Arrays are treated as {@code Iterable} objects.</li> 055 * <li>All other types are directly inserted.</li> 056 * <li>Recursive combinations are supported, e.g. a collection containing an 057 * array that contains strings: The resulting collection will only contain 058 * primitive objects.</li> 059 * </ul> 060 */ 061 @Override 062 public Iterable<?> parse(final Object value) 063 { 064 return flatten(value); 065 } 066 067 /** 068 * {@inheritDoc} This implementation handles the case that the passed in 069 * string is <b>null</b>. In this case, an empty collection is returned. 070 * Otherwise, this method delegates to {@link #splitString(String, boolean)}. 071 */ 072 @Override 073 public Collection<String> split(final String s, final boolean trim) 074 { 075 if (s == null) 076 { 077 return new ArrayList<>(0); 078 } 079 return splitString(s, trim); 080 } 081 082 /** 083 * {@inheritDoc} This implementation checks whether the object to be escaped 084 * is a string. If yes, it delegates to {@link #escapeString(String)}, 085 * otherwise no escaping is performed. Eventually, the passed in transformer 086 * is invoked so that additional encoding can be performed. 087 */ 088 @Override 089 public Object escape(final Object value, final ValueTransformer transformer) 090 { 091 final Object escValue = 092 (value instanceof String) ? escapeString((String) value) 093 : value; 094 return transformer.transformValue(escValue); 095 } 096 097 /** 098 * Actually splits the passed in string which is guaranteed to be not 099 * <b>null</b>. This method is called by the base implementation of the 100 * {@code split()} method. Here the actual splitting logic has to be 101 * implemented. 102 * 103 * @param s the string to be split (not <b>null</b>) 104 * @param trim a flag whether the single components have to be trimmed 105 * @return a collection with the extracted components of the passed in 106 * string 107 */ 108 protected abstract Collection<String> splitString(String s, boolean trim); 109 110 /** 111 * Escapes the specified string. This method is called by {@code escape()} 112 * if the passed in object is a string. Concrete subclasses have to 113 * implement their specific escaping logic here, so that the list delimiters 114 * they support are properly escaped. 115 * 116 * @param s the string to be escaped (not <b>null</b>) 117 * @return the escaped string 118 */ 119 protected abstract String escapeString(String s); 120 121 /** 122 * Extracts all values contained in the specified object up to the given 123 * limit. The passed in object is evaluated (if necessary in a recursive 124 * way). If it is a complex object (e.g. a collection or an array), all its 125 * elements are processed recursively and added to a target collection. The 126 * process stops if the limit is reached, but depending on the input object, 127 * it might be exceeded. (The limit is just an indicator to stop the process 128 * to avoid unnecessary work if the caller is only interested in a few 129 * values.) 130 * 131 * @param value the value to be processed 132 * @param limit the limit for aborting the processing 133 * @return a "flat" collection containing all primitive values of 134 * the passed in object 135 */ 136 Collection<?> flatten(final Object value, final int limit) 137 { 138 if (value instanceof String) 139 { 140 return split((String) value, true); 141 } 142 143 final Collection<Object> result = new LinkedList<>(); 144 if (value instanceof Iterable) 145 { 146 flattenIterator(result, ((Iterable<?>) value).iterator(), limit); 147 } 148 else if (value instanceof Iterator) 149 { 150 flattenIterator(result, (Iterator<?>) value, limit); 151 } 152 else if (value != null) 153 { 154 if (value.getClass().isArray()) 155 { 156 for (int len = Array.getLength(value), idx = 0, size = 0; idx < len 157 && size < limit; idx++, size = result.size()) 158 { 159 result.addAll(flatten(Array.get(value, idx), limit - size)); 160 } 161 } 162 else 163 { 164 result.add(value); 165 } 166 } 167 168 return result; 169 } 170 171 /** 172 * Performs the actual work as advertised by the {@code parse()} method. 173 * This method delegates to {@link #flatten(Object, int)} without specifying 174 * a limit. 175 * 176 * @param value the value to be processed 177 * @return a "flat" collection containing all primitive values of 178 * the passed in object 179 */ 180 private Collection<?> flatten(final Object value) 181 { 182 return flatten(value, Integer.MAX_VALUE); 183 } 184 185 /** 186 * Flattens the given iterator. For each element in the iteration 187 * {@code flatten()} is called recursively. 188 * 189 * @param target the target collection 190 * @param it the iterator to process 191 * @param limit a limit for the number of elements to extract 192 */ 193 private void flattenIterator(final Collection<Object> target, final Iterator<?> it, final int limit) 194 { 195 int size = target.size(); 196 while (size < limit && it.hasNext()) 197 { 198 target.addAll(flatten(it.next(), limit - size)); 199 size = target.size(); 200 } 201 } 202}