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 1842194 2018-09-27 22:24:23Z 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(final 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(final Object value, final 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(final List<?> values, final ValueTransformer transformer) 107 { 108 if (!values.isEmpty()) 109 { 110 final Iterator<?> it = values.iterator(); 111 String lastValue = escapeValue(it.next(), true, transformer); 112 final 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 return null; 130 } 131 132 /** 133 * {@inheritDoc} This implementation simulates the old splitting algorithm. 134 * The string is split at the delimiter character if it is not escaped. If 135 * the delimiter character is not found, the input is returned unchanged. 136 */ 137 @Override 138 protected Collection<String> splitString(final String s, final boolean trim) 139 { 140 if (s.indexOf(getDelimiter()) < 0) 141 { 142 return Collections.singleton(s); 143 } 144 145 final List<String> list = new ArrayList<>(); 146 147 StringBuilder token = new StringBuilder(); 148 int begin = 0; 149 boolean inEscape = false; 150 final char esc = ESCAPE.charAt(0); 151 152 while (begin < s.length()) 153 { 154 final char c = s.charAt(begin); 155 if (inEscape) 156 { 157 // last character was the escape marker 158 // can current character be escaped? 159 if (c != getDelimiter() && c != esc) 160 { 161 // no, also add escape character 162 token.append(esc); 163 } 164 token.append(c); 165 inEscape = false; 166 } 167 168 else 169 { 170 if (c == getDelimiter()) 171 { 172 // found a list delimiter -> add token and 173 // resetDefaultFileSystem buffer 174 String t = token.toString(); 175 if (trim) 176 { 177 t = t.trim(); 178 } 179 list.add(t); 180 token = new StringBuilder(); 181 } 182 else if (c == esc) 183 { 184 // eventually escape next character 185 inEscape = true; 186 } 187 else 188 { 189 token.append(c); 190 } 191 } 192 193 begin++; 194 } 195 196 // Trailing delimiter? 197 if (inEscape) 198 { 199 token.append(esc); 200 } 201 // Add last token 202 String t = token.toString(); 203 if (trim) 204 { 205 t = t.trim(); 206 } 207 list.add(t); 208 209 return list; 210 } 211 212 /** 213 * {@inheritDoc} This is just a dummy implementation. It is never called. 214 */ 215 @Override 216 protected String escapeString(final String s) 217 { 218 return null; 219 } 220 221 /** 222 * Performs the escaping of backslashes in the specified properties value. 223 * Because a double backslash is used to escape the escape character of a 224 * list delimiter, double backslashes also have to be escaped if the 225 * property is part of a (single line) list. In addition, because the output 226 * is written into a properties file, each occurrence of a backslash again 227 * has to be doubled. This method is called by {@code escapeValue()}. 228 * 229 * @param value the value to be escaped 230 * @param inList a flag whether the value is part of a list 231 * @return the value with escaped backslashes as string 232 */ 233 protected String escapeBackslashs(final Object value, final boolean inList) 234 { 235 String strValue = String.valueOf(value); 236 237 if (inList && strValue.indexOf(DOUBLE_ESC) >= 0) 238 { 239 strValue = StringUtils.replace(strValue, DOUBLE_ESC, QUAD_ESC); 240 } 241 242 return strValue; 243 } 244 245 /** 246 * Escapes the given property value. This method is called on saving the 247 * configuration for each property value. It ensures a correct handling of 248 * backslash characters and also takes care that list delimiter characters 249 * in the value are escaped. 250 * 251 * @param value the property value 252 * @param inList a flag whether the value is part of a list 253 * @param transformer the {@code ValueTransformer} 254 * @return the escaped property value 255 */ 256 protected String escapeValue(final Object value, final boolean inList, 257 final ValueTransformer transformer) 258 { 259 String escapedValue = 260 String.valueOf(transformer.transformValue(escapeBackslashs( 261 value, inList))); 262 if (getDelimiter() != 0) 263 { 264 escapedValue = 265 StringUtils.replace(escapedValue, 266 String.valueOf(getDelimiter()), ESCAPE 267 + getDelimiter()); 268 } 269 return escapedValue; 270 } 271 272 /** 273 * Returns the number of trailing backslashes. This is sometimes needed for 274 * the correct handling of escape characters. 275 * 276 * @param line the string to investigate 277 * @return the number of trailing backslashes 278 */ 279 private static int countTrailingBS(final String line) 280 { 281 int bsCount = 0; 282 for (int idx = line.length() - 1; idx >= 0 && line.charAt(idx) == '\\'; idx--) 283 { 284 bsCount++; 285 } 286 287 return bsCount; 288 } 289}