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.util.ArrayList; 020import java.util.Collection; 021import java.util.Collections; 022import java.util.Iterator; 023import java.util.List; 024 025import org.apache.commons.lang3.StringUtils; 026 027/** 028 * <p> 029 * A specialized implementation of {@code ListDelimiterHandler} which simulates 030 * the list delimiter handling as it was used by {@code PropertiesConfiguration} 031 * in Commons Configuration 1.x. 032 * </p> 033 * <p> 034 * This class mainly exists for compatibility reasons. It is intended to be used 035 * by applications which have to deal with properties files created by an older 036 * version of this library. 037 * </p> 038 * <p> 039 * In the 1.x series of Commons Configuration list handling was not fully 040 * consistent. The escaping of property values was done in a different way if 041 * they contained a list delimiter or not. From version 2.0 on, escaping is more 042 * stringent which might cause slightly different results when parsing 043 * properties files created by or for Configuration 1.x. If you encounter such 044 * problems, you can switch to this {@code ListDelimiterHandler} implementation 045 * rather than the default one. In other cases, this class should not be used! 046 * </p> 047 * <p> 048 * Implementation note: An instance of this class can safely be shared between 049 * multiple {@code Configuration} instances. 050 * </p> 051 * 052 * @version $Id: LegacyListDelimiterHandler.java 1790899 2017-04-10 21:56:46Z ggregory $ 053 * @since 2.0 054 */ 055public class LegacyListDelimiterHandler extends AbstractListDelimiterHandler 056{ 057 /** Constant for the escaping character. */ 058 private static final String ESCAPE = "\\"; 059 060 /** Constant for the escaped escaping character. */ 061 private static final String DOUBLE_ESC = ESCAPE + ESCAPE; 062 063 /** Constant for a duplicated sequence of escaping characters. */ 064 private static final String QUAD_ESC = DOUBLE_ESC + DOUBLE_ESC; 065 066 /** The list delimiter character. */ 067 private final char delimiter; 068 069 /** 070 * Creates a new instance of {@code LegacyListDelimiterHandler} and sets the 071 * list delimiter character. 072 * 073 * @param listDelimiter the list delimiter character 074 */ 075 public LegacyListDelimiterHandler(char listDelimiter) 076 { 077 delimiter = listDelimiter; 078 } 079 080 /** 081 * Returns the list delimiter character. 082 * 083 * @return the list delimiter character 084 */ 085 public char getDelimiter() 086 { 087 return delimiter; 088 } 089 090 /** 091 * {@inheritDoc} This implementation performs delimiter escaping for a 092 * single value (which is not part of a list). 093 */ 094 @Override 095 public Object escape(Object value, ValueTransformer transformer) 096 { 097 return escapeValue(value, false, transformer); 098 } 099 100 /** 101 * {@inheritDoc} This implementation performs a special encoding of 102 * backslashes at the end of a string so that they are not interpreted as 103 * escape character for a following list delimiter. 104 */ 105 @Override 106 public Object escapeList(List<?> values, ValueTransformer transformer) 107 { 108 if (!values.isEmpty()) 109 { 110 Iterator<?> it = values.iterator(); 111 String lastValue = escapeValue(it.next(), true, transformer); 112 StringBuilder buf = new StringBuilder(lastValue); 113 while (it.hasNext()) 114 { 115 // if the last value ended with an escape character, it has 116 // to be escaped itself; otherwise the list delimiter will 117 // be escaped 118 if (lastValue.endsWith(ESCAPE) 119 && (countTrailingBS(lastValue) / 2) % 2 != 0) 120 { 121 buf.append(ESCAPE).append(ESCAPE); 122 } 123 buf.append(getDelimiter()); 124 lastValue = escapeValue(it.next(), true, transformer); 125 buf.append(lastValue); 126 } 127 return buf.toString(); 128 } 129 else 130 { 131 return null; 132 } 133 } 134 135 /** 136 * {@inheritDoc} This implementation simulates the old splitting algorithm. 137 * The string is split at the delimiter character if it is not escaped. If 138 * the delimiter character is not found, the input is returned unchanged. 139 */ 140 @Override 141 protected Collection<String> splitString(String s, boolean trim) 142 { 143 if (s.indexOf(getDelimiter()) < 0) 144 { 145 return Collections.singleton(s); 146 } 147 148 List<String> list = new ArrayList<>(); 149 150 StringBuilder token = new StringBuilder(); 151 int begin = 0; 152 boolean inEscape = false; 153 char esc = ESCAPE.charAt(0); 154 155 while (begin < s.length()) 156 { 157 char c = s.charAt(begin); 158 if (inEscape) 159 { 160 // last character was the escape marker 161 // can current character be escaped? 162 if (c != getDelimiter() && c != esc) 163 { 164 // no, also add escape character 165 token.append(esc); 166 } 167 token.append(c); 168 inEscape = false; 169 } 170 171 else 172 { 173 if (c == getDelimiter()) 174 { 175 // found a list delimiter -> add token and 176 // resetDefaultFileSystem buffer 177 String t = token.toString(); 178 if (trim) 179 { 180 t = t.trim(); 181 } 182 list.add(t); 183 token = new StringBuilder(); 184 } 185 else if (c == esc) 186 { 187 // eventually escape next character 188 inEscape = true; 189 } 190 else 191 { 192 token.append(c); 193 } 194 } 195 196 begin++; 197 } 198 199 // Trailing delimiter? 200 if (inEscape) 201 { 202 token.append(esc); 203 } 204 // Add last token 205 String t = token.toString(); 206 if (trim) 207 { 208 t = t.trim(); 209 } 210 list.add(t); 211 212 return list; 213 } 214 215 /** 216 * {@inheritDoc} This is just a dummy implementation. It is never called. 217 */ 218 @Override 219 protected String escapeString(String s) 220 { 221 return null; 222 } 223 224 /** 225 * Performs the escaping of backslashes in the specified properties value. 226 * Because a double backslash is used to escape the escape character of a 227 * list delimiter, double backslashes also have to be escaped if the 228 * property is part of a (single line) list. In addition, because the output 229 * is written into a properties file, each occurrence of a backslash again 230 * has to be doubled. This method is called by {@code escapeValue()}. 231 * 232 * @param value the value to be escaped 233 * @param inList a flag whether the value is part of a list 234 * @return the value with escaped backslashes as string 235 */ 236 protected String escapeBackslashs(Object value, boolean inList) 237 { 238 String strValue = String.valueOf(value); 239 240 if (inList && strValue.indexOf(DOUBLE_ESC) >= 0) 241 { 242 strValue = StringUtils.replace(strValue, DOUBLE_ESC, QUAD_ESC); 243 } 244 245 return strValue; 246 } 247 248 /** 249 * Escapes the given property value. This method is called on saving the 250 * configuration for each property value. It ensures a correct handling of 251 * backslash characters and also takes care that list delimiter characters 252 * in the value are escaped. 253 * 254 * @param value the property value 255 * @param inList a flag whether the value is part of a list 256 * @param transformer the {@code ValueTransformer} 257 * @return the escaped property value 258 */ 259 protected String escapeValue(Object value, boolean inList, 260 ValueTransformer transformer) 261 { 262 String escapedValue = 263 String.valueOf(transformer.transformValue(escapeBackslashs( 264 value, inList))); 265 if (getDelimiter() != 0) 266 { 267 escapedValue = 268 StringUtils.replace(escapedValue, 269 String.valueOf(getDelimiter()), ESCAPE 270 + getDelimiter()); 271 } 272 return escapedValue; 273 } 274 275 /** 276 * Returns the number of trailing backslashes. This is sometimes needed for 277 * the correct handling of escape characters. 278 * 279 * @param line the string to investigate 280 * @return the number of trailing backslashes 281 */ 282 private static int countTrailingBS(String line) 283 { 284 int bsCount = 0; 285 for (int idx = line.length() - 1; idx >= 0 && line.charAt(idx) == '\\'; idx--) 286 { 287 bsCount++; 288 } 289 290 return bsCount; 291 } 292}