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 /**
60 * Returns the number of trailing backslashes. This is sometimes needed for the correct handling of escape characters.
61 *
62 * @param line the string to investigate
63 * @return the number of trailing backslashes
64 */
65 private static int countTrailingBS(final String line) {
66 int bsCount = 0;
67 for (int idx = line.length() - 1; idx >= 0 && line.charAt(idx) == '\\'; idx--) {
68 bsCount++;
69 }
70
71 return bsCount;
72 }
73
74 /** The list delimiter character. */
75 private final char delimiter;
76
77 /**
78 * Creates a new instance of {@code LegacyListDelimiterHandler} and sets the list delimiter character.
79 *
80 * @param listDelimiter the list delimiter character
81 */
82 public LegacyListDelimiterHandler(final char listDelimiter) {
83 delimiter = listDelimiter;
84 }
85
86 /**
87 * {@inheritDoc} This implementation performs delimiter escaping for a single value (which is not part of a list).
88 */
89 @Override
90 public Object escape(final Object value, final ValueTransformer transformer) {
91 return escapeValue(value, false, transformer);
92 }
93
94 /**
95 * Performs the escaping of backslashes in the specified properties value. Because a double backslash is used to escape
96 * the escape character of a list delimiter, double backslashes also have to be escaped if the property is part of a
97 * (single line) list. In addition, because the output is written into a properties file, each occurrence of a backslash
98 * again has to be doubled. This method is called by {@code escapeValue()}.
99 *
100 * @param value the value to be escaped
101 * @param inList a flag whether the value is part of a list
102 * @return the value with escaped backslashes as string
103 */
104 protected String escapeBackslashs(final Object value, final boolean inList) {
105 String strValue = String.valueOf(value);
106
107 if (inList && strValue.contains(DOUBLE_ESC)) {
108 strValue = StringUtils.replace(strValue, DOUBLE_ESC, QUAD_ESC);
109 }
110
111 return strValue;
112 }
113
114 /**
115 * {@inheritDoc} This implementation performs a special encoding of backslashes at the end of a string so that they are
116 * not interpreted as escape character for a following list delimiter.
117 */
118 @Override
119 public Object escapeList(final List<?> values, final ValueTransformer transformer) {
120 if (!values.isEmpty()) {
121 final Iterator<?> it = values.iterator();
122 String lastValue = escapeValue(it.next(), true, transformer);
123 final StringBuilder buf = new StringBuilder(lastValue);
124 while (it.hasNext()) {
125 // if the last value ended with an escape character, it has
126 // to be escaped itself; otherwise the list delimiter will
127 // be escaped
128 if (lastValue.endsWith(ESCAPE) && countTrailingBS(lastValue) / 2 % 2 != 0) {
129 buf.append(ESCAPE).append(ESCAPE);
130 }
131 buf.append(getDelimiter());
132 lastValue = escapeValue(it.next(), true, transformer);
133 buf.append(lastValue);
134 }
135 return buf.toString();
136 }
137 return null;
138 }
139
140 /**
141 * {@inheritDoc} This is just a dummy implementation. It is never called.
142 */
143 @Override
144 protected String escapeString(final String s) {
145 return null;
146 }
147
148 /**
149 * Escapes the given property value. This method is called on saving the configuration for each property value. It
150 * ensures a correct handling of backslash characters and also takes care that list delimiter characters in the value
151 * are escaped.
152 *
153 * @param value the property value
154 * @param inList a flag whether the value is part of a list
155 * @param transformer the {@code ValueTransformer}
156 * @return the escaped property value
157 */
158 protected String escapeValue(final Object value, final boolean inList, final ValueTransformer transformer) {
159 String escapedValue = String.valueOf(transformer.transformValue(escapeBackslashs(value, inList)));
160 if (getDelimiter() != 0) {
161 escapedValue = StringUtils.replace(escapedValue, String.valueOf(getDelimiter()), ESCAPE + getDelimiter());
162 }
163 return escapedValue;
164 }
165
166 /**
167 * Gets the list delimiter character.
168 *
169 * @return the list delimiter character
170 */
171 public char getDelimiter() {
172 return delimiter;
173 }
174
175 /**
176 * {@inheritDoc} This implementation simulates the old splitting algorithm. The string is split at the delimiter
177 * character if it is not escaped. If the delimiter character is not found, the input is returned unchanged.
178 */
179 @Override
180 protected Collection<String> splitString(final String s, final boolean trim) {
181 if (s.indexOf(getDelimiter()) < 0) {
182 return Collections.singleton(s);
183 }
184
185 final List<String> list = new ArrayList<>();
186
187 StringBuilder token = new StringBuilder();
188 int begin = 0;
189 boolean inEscape = false;
190 final char esc = ESCAPE.charAt(0);
191
192 while (begin < s.length()) {
193 final char c = s.charAt(begin);
194 if (inEscape) {
195 // last character was the escape marker
196 // can current character be escaped?
197 if (c != getDelimiter() && c != esc) {
198 // no, also add escape character
199 token.append(esc);
200 }
201 token.append(c);
202 inEscape = false;
203 } else if (c == getDelimiter()) {
204 // found a list delimiter -> add token and
205 // resetDefaultFileSystem buffer
206 String t = token.toString();
207 if (trim) {
208 t = t.trim();
209 }
210 list.add(t);
211 token = new StringBuilder();
212 } else if (c == esc) {
213 // eventually escape next character
214 inEscape = true;
215 } else {
216 token.append(c);
217 }
218
219 begin++;
220 }
221
222 // Trailing delimiter?
223 if (inEscape) {
224 token.append(esc);
225 }
226 // Add last token
227 String t = token.toString();
228 if (trim) {
229 t = t.trim();
230 }
231 list.add(t);
232
233 return list;
234 }
235 }