1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.configuration2.convert;
18
19 import java.util.ArrayList;
20 import java.util.Collection;
21 import java.util.Collections;
22 import java.util.Iterator;
23 import java.util.List;
24
25 import org.apache.commons.lang3.StringUtils;
26
27 /**
28 * <p>
29 * A specialized implementation of {@code ListDelimiterHandler} which simulates the list delimiter handling as it was
30 * used by {@code PropertiesConfiguration} in Commons Configuration 1.x.
31 * </p>
32 * <p>
33 * This class mainly exists for compatibility reasons. It is intended to be used by applications which have to deal with
34 * properties files created by an older version of this library.
35 * </p>
36 * <p>
37 * In the 1.x series of Commons Configuration list handling was not fully consistent. The escaping of property values
38 * was done in a different way if they contained a list delimiter or not. From version 2.0 on, escaping is more
39 * stringent which might cause slightly different results when parsing properties files created by or for Configuration
40 * 1.x. If you encounter such problems, you can switch to this {@code ListDelimiterHandler} implementation rather than
41 * the default one. In other cases, this class should not be used!
42 * </p>
43 * <p>
44 * Implementation note: An instance of this class can safely be shared between multiple {@code Configuration} instances.
45 * </p>
46 *
47 * @since 2.0
48 */
49 public class LegacyListDelimiterHandler extends AbstractListDelimiterHandler {
50 /** Constant for the escaping character. */
51 private static final String ESCAPE = "\\";
52
53 /** Constant for the escaped escaping character. */
54 private static final String DOUBLE_ESC = ESCAPE + ESCAPE;
55
56 /** Constant for a duplicated sequence of escaping characters. */
57 private static final String QUAD_ESC = DOUBLE_ESC + DOUBLE_ESC;
58
59 /** The list delimiter character. */
60 private final char delimiter;
61
62 /**
63 * Creates a new instance of {@code LegacyListDelimiterHandler} and sets the list delimiter character.
64 *
65 * @param listDelimiter the list delimiter character
66 */
67 public LegacyListDelimiterHandler(final char listDelimiter) {
68 delimiter = listDelimiter;
69 }
70
71 /**
72 * Gets the list delimiter character.
73 *
74 * @return the list delimiter character
75 */
76 public char getDelimiter() {
77 return delimiter;
78 }
79
80 /**
81 * {@inheritDoc} This implementation performs delimiter escaping for a single value (which is not part of a list).
82 */
83 @Override
84 public Object escape(final Object value, final ValueTransformer transformer) {
85 return escapeValue(value, false, transformer);
86 }
87
88 /**
89 * {@inheritDoc} This implementation performs a special encoding of backslashes at the end of a string so that they are
90 * not interpreted as escape character for a following list delimiter.
91 */
92 @Override
93 public Object escapeList(final List<?> values, final ValueTransformer transformer) {
94 if (!values.isEmpty()) {
95 final Iterator<?> it = values.iterator();
96 String lastValue = escapeValue(it.next(), true, transformer);
97 final StringBuilder buf = new StringBuilder(lastValue);
98 while (it.hasNext()) {
99 // 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 }