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