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