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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.lang3.text;
18  
19  import java.util.ArrayList;
20  import java.util.Enumeration;
21  import java.util.HashMap;
22  import java.util.List;
23  import java.util.Map;
24  import java.util.Objects;
25  import java.util.Properties;
26  
27  import org.apache.commons.lang3.StringUtils;
28  
29  /**
30   * Substitutes variables within a string by values.
31   * <p>
32   * This class takes a piece of text and substitutes all the variables within it.
33   * The default definition of a variable is {@code ${variableName}}.
34   * The prefix and suffix can be changed via constructors and set methods.
35   * </p>
36   * <p>
37   * Variable values are typically resolved from a map, but could also be resolved
38   * from system properties, or by supplying a custom variable resolver.
39   * </p>
40   * <p>
41   * The simplest example is to use this class to replace Java System properties. For example:
42   * </p>
43   * <pre>
44   * StrSubstitutor.replaceSystemProperties(
45   *      "You are running with java.version = ${java.version} and os.name = ${os.name}.");
46   * </pre>
47   * <p>
48   * Typical usage of this class follows the following pattern: First an instance is created
49   * and initialized with the map that contains the values for the available variables.
50   * If a prefix and/or suffix for variables should be used other than the default ones,
51   * the appropriate settings can be performed. After that the {@code replace()}
52   * method can be called passing in the source text for interpolation. In the returned
53   * text all variable references (as long as their values are known) will be resolved.
54   * The following example demonstrates this:
55   * </p>
56   * <pre>
57   * Map valuesMap = HashMap();
58   * valuesMap.put(&quot;animal&quot;, &quot;quick brown fox&quot;);
59   * valuesMap.put(&quot;target&quot;, &quot;lazy dog&quot;);
60   * String templateString = &quot;The ${animal} jumps over the ${target}.&quot;;
61   * StrSubstitutor sub = new StrSubstitutor(valuesMap);
62   * String resolvedString = sub.replace(templateString);
63   * </pre>
64   * yielding:
65   * <pre>
66   *      The quick brown fox jumps over the lazy dog.
67   * </pre>
68   * <p>
69   * Also, this class allows to set a default value for unresolved variables.
70   * The default value for a variable can be appended to the variable name after the variable
71   * default value delimiter. The default value of the variable default value delimiter is ':-',
72   * as in bash and other *nix shells, as those are arguably where the default ${} delimiter set originated.
73   * The variable default value delimiter can be manually set by calling {@link #setValueDelimiterMatcher(StrMatcher)},
74   * {@link #setValueDelimiter(char)} or {@link #setValueDelimiter(String)}.
75   * The following shows an example with variable default value settings:
76   * </p>
77   * <pre>
78   * Map valuesMap = HashMap();
79   * valuesMap.put(&quot;animal&quot;, &quot;quick brown fox&quot;);
80   * valuesMap.put(&quot;target&quot;, &quot;lazy dog&quot;);
81   * String templateString = &quot;The ${animal} jumps over the ${target}. ${undefined.number:-1234567890}.&quot;;
82   * StrSubstitutor sub = new StrSubstitutor(valuesMap);
83   * String resolvedString = sub.replace(templateString);
84   * </pre>
85   * <p>
86   * yielding:
87   * </p>
88   * <pre>
89   *      The quick brown fox jumps over the lazy dog. 1234567890.
90   * </pre>
91   * <p>
92   * In addition to this usage pattern there are some static convenience methods that
93   * cover the most common use cases. These methods can be used without the need of
94   * manually creating an instance. However if multiple replace operations are to be
95   * performed, creating and reusing an instance of this class will be more efficient.
96   * </p>
97   * <p>
98   * Variable replacement works in a recursive way. Thus, if a variable value contains
99   * a variable then that variable will also be replaced. Cyclic replacements are
100  * detected and will cause an exception to be thrown.
101  * </p>
102  * <p>
103  * Sometimes the interpolation's result must contain a variable prefix. As an example
104  * take the following source text:
105  * </p>
106  * <pre>
107  *   The variable ${${name}} must be used.
108  * </pre>
109  * <p>
110  * Here only the variable's name referred to in the text should be replaced resulting
111  * in the text (assuming that the value of the {@code name} variable is {@code x}):
112  * </p>
113  * <pre>
114  *   The variable ${x} must be used.
115  * </pre>
116  * <p>
117  * To achieve this effect there are two possibilities: Either set a different prefix
118  * and suffix for variables which do not conflict with the result text you want to
119  * produce. The other possibility is to use the escape character, by default '$'.
120  * If this character is placed before a variable reference, this reference is ignored
121  * and won't be replaced. For example:
122  * </p>
123  * <pre>
124  *   The variable $${${name}} must be used.
125  * </pre>
126  * <p>
127  * In some complex scenarios you might even want to perform substitution in the
128  * names of variables, for instance:
129  * </p>
130  * <pre>
131  * ${jre-${java.specification.version}}
132  * </pre>
133  * <p>
134  * {@link StrSubstitutor} supports this recursive substitution in variable
135  * names, but it has to be enabled explicitly by setting the
136  * {@link #setEnableSubstitutionInVariables(boolean) enableSubstitutionInVariables}
137  * property to <b>true</b>.
138  * </p>
139  * <p>
140  * This class is <b>not</b> thread safe.
141  * </p>
142  *
143  * @since 2.2
144  * @deprecated As of 3.6, use Apache Commons Text
145  * <a href="https://commons.apache.org/proper/commons-text/javadocs/api-release/org/apache/commons/text/StringSubstitutor.html">
146  * StringSubstitutor</a> instead
147  */
148 @Deprecated
149 public class StrSubstitutor {
150 
151     /**
152      * Constant for the default escape character.
153      */
154     public static final char DEFAULT_ESCAPE = '$';
155     /**
156      * Constant for the default variable prefix.
157      */
158     public static final StrMatcher DEFAULT_PREFIX = StrMatcher.stringMatcher("${");
159     /**
160      * Constant for the default variable suffix.
161      */
162     public static final StrMatcher DEFAULT_SUFFIX = StrMatcher.stringMatcher("}");
163     /**
164      * Constant for the default value delimiter of a variable.
165      * @since 3.2
166      */
167     public static final StrMatcher DEFAULT_VALUE_DELIMITER = StrMatcher.stringMatcher(":-");
168 
169     /**
170      * Stores the escape character.
171      */
172     private char escapeChar;
173     /**
174      * Stores the variable prefix.
175      */
176     private StrMatcher prefixMatcher;
177     /**
178      * Stores the variable suffix.
179      */
180     private StrMatcher suffixMatcher;
181     /**
182      * Stores the default variable value delimiter
183      */
184     private StrMatcher valueDelimiterMatcher;
185     /**
186      * Variable resolution is delegated to an implementor of VariableResolver.
187      */
188     private StrLookup<?> variableResolver;
189     /**
190      * The flag whether substitution in variable names is enabled.
191      */
192     private boolean enableSubstitutionInVariables;
193     /**
194      * Whether escapes should be preserved.  Default is false;
195      */
196     private boolean preserveEscapes;
197 
198     /**
199      * Replaces all the occurrences of variables in the given source object with
200      * their matching values from the map.
201      *
202      * @param <V> the type of the values in the map
203      * @param source  the source text containing the variables to substitute, null returns null
204      * @param valueMap  the map with the values, may be null
205      * @return the result of the replace operation
206      */
207     public static <V> String replace(final Object source, final Map<String, V> valueMap) {
208         return new StrSubstitutor(valueMap).replace(source);
209     }
210 
211     /**
212      * Replaces all the occurrences of variables in the given source object with
213      * their matching values from the map. This method allows to specify a
214      * custom variable prefix and suffix
215      *
216      * @param <V> the type of the values in the map
217      * @param source  the source text containing the variables to substitute, null returns null
218      * @param valueMap  the map with the values, may be null
219      * @param prefix  the prefix of variables, not null
220      * @param suffix  the suffix of variables, not null
221      * @return the result of the replace operation
222      * @throws IllegalArgumentException if the prefix or suffix is null
223      */
224     public static <V> String replace(final Object source, final Map<String, V> valueMap, final String prefix, final String suffix) {
225         return new StrSubstitutor(valueMap, prefix, suffix).replace(source);
226     }
227 
228     /**
229      * Replaces all the occurrences of variables in the given source object with their matching
230      * values from the properties.
231      *
232      * @param source the source text containing the variables to substitute, null returns null
233      * @param valueProperties the properties with values, may be null
234      * @return the result of the replace operation
235      */
236     public static String replace(final Object source, final Properties valueProperties) {
237         if (valueProperties == null) {
238             return source.toString();
239         }
240         final Map<String, String> valueMap = new HashMap<>();
241         final Enumeration<?> propNames = valueProperties.propertyNames();
242         while (propNames.hasMoreElements()) {
243             final String propName = String.valueOf(propNames.nextElement());
244             final String propValue = valueProperties.getProperty(propName);
245             valueMap.put(propName, propValue);
246         }
247         return replace(source, valueMap);
248     }
249 
250     /**
251      * Replaces all the occurrences of variables in the given source object with
252      * their matching values from the system properties.
253      *
254      * @param source  the source text containing the variables to substitute, null returns null
255      * @return the result of the replace operation
256      */
257     public static String replaceSystemProperties(final Object source) {
258         return new StrSubstitutor(StrLookup.systemPropertiesLookup()).replace(source);
259     }
260 
261     /**
262      * Creates a new instance with defaults for variable prefix and suffix
263      * and the escaping character.
264      */
265     public StrSubstitutor() {
266         this(null, DEFAULT_PREFIX, DEFAULT_SUFFIX, DEFAULT_ESCAPE);
267     }
268 
269     /**
270      * Creates a new instance and initializes it. Uses defaults for variable
271      * prefix and suffix and the escaping character.
272      *
273      * @param <V> the type of the values in the map
274      * @param valueMap  the map with the variables' values, may be null
275      */
276     public <V> StrSubstitutor(final Map<String, V> valueMap) {
277         this(StrLookup.mapLookup(valueMap), DEFAULT_PREFIX, DEFAULT_SUFFIX, DEFAULT_ESCAPE);
278     }
279 
280     /**
281      * Creates a new instance and initializes it. Uses a default escaping character.
282      *
283      * @param <V> the type of the values in the map
284      * @param valueMap  the map with the variables' values, may be null
285      * @param prefix  the prefix for variables, not null
286      * @param suffix  the suffix for variables, not null
287      * @throws IllegalArgumentException if the prefix or suffix is null
288      */
289     public <V> StrSubstitutor(final Map<String, V> valueMap, final String prefix, final String suffix) {
290         this(StrLookup.mapLookup(valueMap), prefix, suffix, DEFAULT_ESCAPE);
291     }
292 
293     /**
294      * Creates a new instance and initializes it.
295      *
296      * @param <V> the type of the values in the map
297      * @param valueMap  the map with the variables' values, may be null
298      * @param prefix  the prefix for variables, not null
299      * @param suffix  the suffix for variables, not null
300      * @param escape  the escape character
301      * @throws IllegalArgumentException if the prefix or suffix is null
302      */
303     public <V> StrSubstitutor(final Map<String, V> valueMap, final String prefix, final String suffix,
304                               final char escape) {
305         this(StrLookup.mapLookup(valueMap), prefix, suffix, escape);
306     }
307 
308     /**
309      * Creates a new instance and initializes it.
310      *
311      * @param <V> the type of the values in the map
312      * @param valueMap  the map with the variables' values, may be null
313      * @param prefix  the prefix for variables, not null
314      * @param suffix  the suffix for variables, not null
315      * @param escape  the escape character
316      * @param valueDelimiter  the variable default value delimiter, may be null
317      * @throws IllegalArgumentException if the prefix or suffix is null
318      * @since 3.2
319      */
320     public <V> StrSubstitutor(final Map<String, V> valueMap, final String prefix, final String suffix,
321                               final char escape, final String valueDelimiter) {
322         this(StrLookup.mapLookup(valueMap), prefix, suffix, escape, valueDelimiter);
323     }
324 
325     /**
326      * Creates a new instance and initializes it.
327      *
328      * @param variableResolver  the variable resolver, may be null
329      */
330     public StrSubstitutor(final StrLookup<?> variableResolver) {
331         this(variableResolver, DEFAULT_PREFIX, DEFAULT_SUFFIX, DEFAULT_ESCAPE);
332     }
333 
334     /**
335      * Creates a new instance and initializes it.
336      *
337      * @param variableResolver  the variable resolver, may be null
338      * @param prefix  the prefix for variables, not null
339      * @param suffix  the suffix for variables, not null
340      * @param escape  the escape character
341      * @throws IllegalArgumentException if the prefix or suffix is null
342      */
343     public StrSubstitutor(final StrLookup<?> variableResolver, final String prefix, final String suffix,
344                           final char escape) {
345         this.setVariableResolver(variableResolver);
346         this.setVariablePrefix(prefix);
347         this.setVariableSuffix(suffix);
348         this.setEscapeChar(escape);
349         this.setValueDelimiterMatcher(DEFAULT_VALUE_DELIMITER);
350     }
351 
352     /**
353      * Creates a new instance and initializes it.
354      *
355      * @param variableResolver  the variable resolver, may be null
356      * @param prefix  the prefix for variables, not null
357      * @param suffix  the suffix for variables, not null
358      * @param escape  the escape character
359      * @param valueDelimiter  the variable default value delimiter string, may be null
360      * @throws IllegalArgumentException if the prefix or suffix is null
361      * @since 3.2
362      */
363     public StrSubstitutor(final StrLookup<?> variableResolver, final String prefix, final String suffix,
364                           final char escape, final String valueDelimiter) {
365         this.setVariableResolver(variableResolver);
366         this.setVariablePrefix(prefix);
367         this.setVariableSuffix(suffix);
368         this.setEscapeChar(escape);
369         this.setValueDelimiter(valueDelimiter);
370     }
371 
372     /**
373      * Creates a new instance and initializes it.
374      *
375      * @param variableResolver  the variable resolver, may be null
376      * @param prefixMatcher  the prefix for variables, not null
377      * @param suffixMatcher  the suffix for variables, not null
378      * @param escape  the escape character
379      * @throws IllegalArgumentException if the prefix or suffix is null
380      */
381     public StrSubstitutor(
382             final StrLookup<?> variableResolver, final StrMatcher prefixMatcher, final StrMatcher suffixMatcher,
383             final char escape) {
384         this(variableResolver, prefixMatcher, suffixMatcher, escape, DEFAULT_VALUE_DELIMITER);
385     }
386 
387     /**
388      * Creates a new instance and initializes it.
389      *
390      * @param variableResolver  the variable resolver, may be null
391      * @param prefixMatcher  the prefix for variables, not null
392      * @param suffixMatcher  the suffix for variables, not null
393      * @param escape  the escape character
394      * @param valueDelimiterMatcher  the variable default value delimiter matcher, may be null
395      * @throws IllegalArgumentException if the prefix or suffix is null
396      * @since 3.2
397      */
398     public StrSubstitutor(
399             final StrLookup<?> variableResolver, final StrMatcher prefixMatcher, final StrMatcher suffixMatcher,
400             final char escape, final StrMatcher valueDelimiterMatcher) {
401         this.setVariableResolver(variableResolver);
402         this.setVariablePrefixMatcher(prefixMatcher);
403         this.setVariableSuffixMatcher(suffixMatcher);
404         this.setEscapeChar(escape);
405         this.setValueDelimiterMatcher(valueDelimiterMatcher);
406     }
407 
408     /**
409      * Replaces all the occurrences of variables with their matching values
410      * from the resolver using the given source string as a template.
411      *
412      * @param source  the string to replace in, null returns null
413      * @return the result of the replace operation
414      */
415     public String replace(final String source) {
416         if (source == null) {
417             return null;
418         }
419         final StrBuilder buf = new StrBuilder(source);
420         if (!substitute(buf, 0, source.length())) {
421             return source;
422         }
423         return buf.toString();
424     }
425 
426     /**
427      * Replaces all the occurrences of variables with their matching values
428      * from the resolver using the given source string as a template.
429      * <p>
430      * Only the specified portion of the string will be processed.
431      * The rest of the string is not processed, and is not returned.
432      * </p>
433      *
434      * @param source  the string to replace in, null returns null
435      * @param offset  the start offset within the array, must be valid
436      * @param length  the length within the array to be processed, must be valid
437      * @return the result of the replace operation
438      */
439     public String replace(final String source, final int offset, final int length) {
440         if (source == null) {
441             return null;
442         }
443         final StrBuilder buf = new StrBuilder(length).append(source, offset, length);
444         if (!substitute(buf, 0, length)) {
445             return source.substring(offset, offset + length);
446         }
447         return buf.toString();
448     }
449 
450     /**
451      * Replaces all the occurrences of variables with their matching values
452      * from the resolver using the given source array as a template.
453      * The array is not altered by this method.
454      *
455      * @param source  the character array to replace in, not altered, null returns null
456      * @return the result of the replace operation
457      */
458     public String replace(final char[] source) {
459         if (source == null) {
460             return null;
461         }
462         final StrBuilder buf = new StrBuilder(source.length).append(source);
463         substitute(buf, 0, source.length);
464         return buf.toString();
465     }
466 
467     /**
468      * Replaces all the occurrences of variables with their matching values
469      * from the resolver using the given source array as a template.
470      * The array is not altered by this method.
471      * <p>
472      * Only the specified portion of the array will be processed.
473      * The rest of the array is not processed, and is not returned.
474      * </p>
475      *
476      * @param source  the character array to replace in, not altered, null returns null
477      * @param offset  the start offset within the array, must be valid
478      * @param length  the length within the array to be processed, must be valid
479      * @return the result of the replace operation
480      */
481     public String replace(final char[] source, final int offset, final int length) {
482         if (source == null) {
483             return null;
484         }
485         final StrBuilder buf = new StrBuilder(length).append(source, offset, length);
486         substitute(buf, 0, length);
487         return buf.toString();
488     }
489 
490     /**
491      * Replaces all the occurrences of variables with their matching values
492      * from the resolver using the given source buffer as a template.
493      * The buffer is not altered by this method.
494      *
495      * @param source  the buffer to use as a template, not changed, null returns null
496      * @return the result of the replace operation
497      */
498     public String replace(final StringBuffer source) {
499         if (source == null) {
500             return null;
501         }
502         final StrBuilder buf = new StrBuilder(source.length()).append(source);
503         substitute(buf, 0, buf.length());
504         return buf.toString();
505     }
506 
507     /**
508      * Replaces all the occurrences of variables with their matching values
509      * from the resolver using the given source buffer as a template.
510      * The buffer is not altered by this method.
511      * <p>
512      * Only the specified portion of the buffer will be processed.
513      * The rest of the buffer is not processed, and is not returned.
514      * </p>
515      *
516      * @param source  the buffer to use as a template, not changed, null returns null
517      * @param offset  the start offset within the array, must be valid
518      * @param length  the length within the array to be processed, must be valid
519      * @return the result of the replace operation
520      */
521     public String replace(final StringBuffer source, final int offset, final int length) {
522         if (source == null) {
523             return null;
524         }
525         final StrBuilder buf = new StrBuilder(length).append(source, offset, length);
526         substitute(buf, 0, length);
527         return buf.toString();
528     }
529 
530     /**
531      * Replaces all the occurrences of variables with their matching values
532      * from the resolver using the given source as a template.
533      * The source is not altered by this method.
534      *
535      * @param source  the buffer to use as a template, not changed, null returns null
536      * @return the result of the replace operation
537      * @since 3.2
538      */
539     public String replace(final CharSequence source) {
540         if (source == null) {
541             return null;
542         }
543         return replace(source, 0, source.length());
544     }
545 
546     /**
547      * Replaces all the occurrences of variables with their matching values
548      * from the resolver using the given source as a template.
549      * The source is not altered by this method.
550      * <p>
551      * Only the specified portion of the buffer will be processed.
552      * The rest of the buffer is not processed, and is not returned.
553      * </p>
554      *
555      * @param source  the buffer to use as a template, not changed, null returns null
556      * @param offset  the start offset within the array, must be valid
557      * @param length  the length within the array to be processed, must be valid
558      * @return the result of the replace operation
559      * @since 3.2
560      */
561     public String replace(final CharSequence source, final int offset, final int length) {
562         if (source == null) {
563             return null;
564         }
565         final StrBuilder buf = new StrBuilder(length).append(source, offset, length);
566         substitute(buf, 0, length);
567         return buf.toString();
568     }
569 
570     /**
571      * Replaces all the occurrences of variables with their matching values
572      * from the resolver using the given source builder as a template.
573      * The builder is not altered by this method.
574      *
575      * @param source  the builder to use as a template, not changed, null returns null
576      * @return the result of the replace operation
577      */
578     public String replace(final StrBuilder source) {
579         if (source == null) {
580             return null;
581         }
582         final StrBuilder buf = new StrBuilder(source.length()).append(source);
583         substitute(buf, 0, buf.length());
584         return buf.toString();
585     }
586 
587     /**
588      * Replaces all the occurrences of variables with their matching values
589      * from the resolver using the given source builder as a template.
590      * The builder is not altered by this method.
591      * <p>
592      * Only the specified portion of the builder will be processed.
593      * The rest of the builder is not processed, and is not returned.
594      * </p>
595      *
596      * @param source  the builder to use as a template, not changed, null returns null
597      * @param offset  the start offset within the array, must be valid
598      * @param length  the length within the array to be processed, must be valid
599      * @return the result of the replace operation
600      */
601     public String replace(final StrBuilder source, final int offset, final int length) {
602         if (source == null) {
603             return null;
604         }
605         final StrBuilder buf = new StrBuilder(length).append(source, offset, length);
606         substitute(buf, 0, length);
607         return buf.toString();
608     }
609 
610     /**
611      * Replaces all the occurrences of variables in the given source object with
612      * their matching values from the resolver. The input source object is
613      * converted to a string using {@code toString} and is not altered.
614      *
615      * @param source  the source to replace in, null returns null
616      * @return the result of the replace operation
617      */
618     public String replace(final Object source) {
619         if (source == null) {
620             return null;
621         }
622         final StrBuilder buf = new StrBuilder().append(source);
623         substitute(buf, 0, buf.length());
624         return buf.toString();
625     }
626 
627     /**
628      * Replaces all the occurrences of variables within the given source buffer
629      * with their matching values from the resolver.
630      * The buffer is updated with the result.
631      *
632      * @param source  the buffer to replace in, updated, null returns zero
633      * @return true if altered
634      */
635     public boolean replaceIn(final StringBuffer source) {
636         if (source == null) {
637             return false;
638         }
639         return replaceIn(source, 0, source.length());
640     }
641 
642     /**
643      * Replaces all the occurrences of variables within the given source buffer
644      * with their matching values from the resolver.
645      * The buffer is updated with the result.
646      * <p>
647      * Only the specified portion of the buffer will be processed.
648      * The rest of the buffer is not processed, but it is not deleted.
649      * </p>
650      *
651      * @param source  the buffer to replace in, updated, null returns zero
652      * @param offset  the start offset within the array, must be valid
653      * @param length  the length within the buffer to be processed, must be valid
654      * @return true if altered
655      */
656     public boolean replaceIn(final StringBuffer source, final int offset, final int length) {
657         if (source == null) {
658             return false;
659         }
660         final StrBuilder buf = new StrBuilder(length).append(source, offset, length);
661         if (!substitute(buf, 0, length)) {
662             return false;
663         }
664         source.replace(offset, offset + length, buf.toString());
665         return true;
666     }
667 
668     /**
669      * Replaces all the occurrences of variables within the given source buffer
670      * with their matching values from the resolver.
671      * The buffer is updated with the result.
672      *
673      * @param source  the buffer to replace in, updated, null returns zero
674      * @return true if altered
675      * @since 3.2
676      */
677     public boolean replaceIn(final StringBuilder source) {
678         if (source == null) {
679             return false;
680         }
681         return replaceIn(source, 0, source.length());
682     }
683 
684     /**
685      * Replaces all the occurrences of variables within the given source builder
686      * with their matching values from the resolver.
687      * The builder is updated with the result.
688      * <p>
689      * Only the specified portion of the buffer will be processed.
690      * The rest of the buffer is not processed, but it is not deleted.
691      * </p>
692      *
693      * @param source  the buffer to replace in, updated, null returns zero
694      * @param offset  the start offset within the array, must be valid
695      * @param length  the length within the buffer to be processed, must be valid
696      * @return true if altered
697      * @since 3.2
698      */
699     public boolean replaceIn(final StringBuilder source, final int offset, final int length) {
700         if (source == null) {
701             return false;
702         }
703         final StrBuilder buf = new StrBuilder(length).append(source, offset, length);
704         if (!substitute(buf, 0, length)) {
705             return false;
706         }
707         source.replace(offset, offset + length, buf.toString());
708         return true;
709     }
710 
711     /**
712      * Replaces all the occurrences of variables within the given source
713      * builder with their matching values from the resolver.
714      *
715      * @param source  the builder to replace in, updated, null returns zero
716      * @return true if altered
717      */
718     public boolean replaceIn(final StrBuilder source) {
719         if (source == null) {
720             return false;
721         }
722         return substitute(source, 0, source.length());
723     }
724 
725     /**
726      * Replaces all the occurrences of variables within the given source
727      * builder with their matching values from the resolver.
728      * <p>
729      * Only the specified portion of the builder will be processed.
730      * The rest of the builder is not processed, but it is not deleted.
731      * </p>
732      *
733      * @param source  the builder to replace in, null returns zero
734      * @param offset  the start offset within the array, must be valid
735      * @param length  the length within the builder to be processed, must be valid
736      * @return true if altered
737      */
738     public boolean replaceIn(final StrBuilder source, final int offset, final int length) {
739         if (source == null) {
740             return false;
741         }
742         return substitute(source, offset, length);
743     }
744 
745     /**
746      * Internal method that substitutes the variables.
747      * <p>
748      * Most users of this class do not need to call this method. This method will
749      * be called automatically by another (public) method.
750      * </p>
751      * <p>
752      * Writers of subclasses can override this method if they need access to
753      * the substitution process at the start or end.
754      * </p>
755      *
756      * @param buf  the string builder to substitute into, not null
757      * @param offset  the start offset within the builder, must be valid
758      * @param length  the length within the builder to be processed, must be valid
759      * @return true if altered
760      */
761     protected boolean substitute(final StrBuilder buf, final int offset, final int length) {
762         return substitute(buf, offset, length, null) > 0;
763     }
764 
765     /**
766      * Recursive handler for multiple levels of interpolation. This is the main
767      * interpolation method, which resolves the values of all variable references
768      * contained in the passed-in text.
769      *
770      * @param buf  the string builder to substitute into, not null
771      * @param offset  the start offset within the builder, must be valid
772      * @param length  the length within the builder to be processed, must be valid
773      * @param priorVariables  the stack keeping track of the replaced variables, may be null
774      * @return the length change that occurs, unless priorVariables is null when the int
775      *  represents a boolean flag as to whether any change occurred.
776      */
777     private int substitute(final StrBuilder buf, final int offset, final int length, List<String> priorVariables) {
778         final StrMatcher pfxMatcher = getVariablePrefixMatcher();
779         final StrMatcher suffMatcher = getVariableSuffixMatcher();
780         final char escape = getEscapeChar();
781         final StrMatcher valueDelimMatcher = getValueDelimiterMatcher();
782         final boolean substitutionInVariablesEnabled = isEnableSubstitutionInVariables();
783 
784         final boolean top = priorVariables == null;
785         boolean altered = false;
786         int lengthChange = 0;
787         char[] chars = buf.buffer;
788         int bufEnd = offset + length;
789         int pos = offset;
790         while (pos < bufEnd) {
791             final int startMatchLen = pfxMatcher.isMatch(chars, pos, offset,
792                     bufEnd);
793             if (startMatchLen == 0) {
794                 pos++;
795             } else // found variable start marker
796             if (pos > offset && chars[pos - 1] == escape) {
797                 // escaped
798                 if (preserveEscapes) {
799                     pos++;
800                     continue;
801                 }
802                 buf.deleteCharAt(pos - 1);
803                 chars = buf.buffer; // in case buffer was altered
804                 lengthChange--;
805                 altered = true;
806                 bufEnd--;
807             } else {
808                 // find suffix
809                 final int startPos = pos;
810                 pos += startMatchLen;
811                 int endMatchLen;
812                 int nestedVarCount = 0;
813                 while (pos < bufEnd) {
814                     if (substitutionInVariablesEnabled
815                             && (endMatchLen = pfxMatcher.isMatch(chars,
816                                     pos, offset, bufEnd)) != 0) {
817                         // found a nested variable start
818                         nestedVarCount++;
819                         pos += endMatchLen;
820                         continue;
821                     }
822 
823                     endMatchLen = suffMatcher.isMatch(chars, pos, offset,
824                             bufEnd);
825                     if (endMatchLen == 0) {
826                         pos++;
827                     } else {
828                         // found variable end marker
829                         if (nestedVarCount == 0) {
830                             String varNameExpr = new String(chars, startPos
831                                     + startMatchLen, pos - startPos
832                                     - startMatchLen);
833                             if (substitutionInVariablesEnabled) {
834                                 final StrBuilder bufName = new StrBuilder(varNameExpr);
835                                 substitute(bufName, 0, bufName.length());
836                                 varNameExpr = bufName.toString();
837                             }
838                             pos += endMatchLen;
839                             final int endPos = pos;
840 
841                             String varName = varNameExpr;
842                             String varDefaultValue = null;
843 
844                             if (valueDelimMatcher != null) {
845                                 final char [] varNameExprChars = varNameExpr.toCharArray();
846                                 int valueDelimiterMatchLen;
847                                 for (int i = 0; i < varNameExprChars.length; i++) {
848                                     // if there's any nested variable when nested variable substitution disabled, then stop resolving name and default value.
849                                     if (!substitutionInVariablesEnabled
850                                             && pfxMatcher.isMatch(varNameExprChars, i, i, varNameExprChars.length) != 0) {
851                                         break;
852                                     }
853                                     if ((valueDelimiterMatchLen = valueDelimMatcher.isMatch(varNameExprChars, i)) != 0) {
854                                         varName = varNameExpr.substring(0, i);
855                                         varDefaultValue = varNameExpr.substring(i + valueDelimiterMatchLen);
856                                         break;
857                                     }
858                                 }
859                             }
860 
861                             // on the first call initialize priorVariables
862                             if (priorVariables == null) {
863                                 priorVariables = new ArrayList<>();
864                                 priorVariables.add(new String(chars,
865                                         offset, length));
866                             }
867 
868                             // handle cyclic substitution
869                             checkCyclicSubstitution(varName, priorVariables);
870                             priorVariables.add(varName);
871 
872                             // resolve the variable
873                             String varValue = resolveVariable(varName, buf,
874                                     startPos, endPos);
875                             if (varValue == null) {
876                                 varValue = varDefaultValue;
877                             }
878                             if (varValue != null) {
879                                 // recursive replace
880                                 final int varLen = varValue.length();
881                                 buf.replace(startPos, endPos, varValue);
882                                 altered = true;
883                                 int change = substitute(buf, startPos,
884                                         varLen, priorVariables);
885                                 change = change
886                                         + varLen - (endPos - startPos);
887                                 pos += change;
888                                 bufEnd += change;
889                                 lengthChange += change;
890                                 chars = buf.buffer; // in case buffer was
891                                                     // altered
892                             }
893 
894                             // remove variable from the cyclic stack
895                             priorVariables
896                                     .remove(priorVariables.size() - 1);
897                             break;
898                         }
899                         nestedVarCount--;
900                         pos += endMatchLen;
901                     }
902                 }
903             }
904         }
905         if (top) {
906             return altered ? 1 : 0;
907         }
908         return lengthChange;
909     }
910 
911     /**
912      * Checks if the specified variable is already in the stack (list) of variables.
913      *
914      * @param varName  the variable name to check
915      * @param priorVariables  the list of prior variables
916      */
917     private void checkCyclicSubstitution(final String varName, final List<String> priorVariables) {
918         if (!priorVariables.contains(varName)) {
919             return;
920         }
921         final StrBuilder buf = new StrBuilder(256);
922         buf.append("Infinite loop in property interpolation of ");
923         buf.append(priorVariables.remove(0));
924         buf.append(": ");
925         buf.appendWithSeparators(priorVariables, "->");
926         throw new IllegalStateException(buf.toString());
927     }
928 
929     /**
930      * Internal method that resolves the value of a variable.
931      * <p>
932      * Most users of this class do not need to call this method. This method is
933      * called automatically by the substitution process.
934      * </p>
935      * <p>
936      * Writers of subclasses can override this method if they need to alter
937      * how each substitution occurs. The method is passed the variable's name
938      * and must return the corresponding value. This implementation uses the
939      * {@link #getVariableResolver()} with the variable's name as the key.
940      * </p>
941      *
942      * @param variableName  the name of the variable, not null
943      * @param buf  the buffer where the substitution is occurring, not null
944      * @param startPos  the start position of the variable including the prefix, valid
945      * @param endPos  the end position of the variable including the suffix, valid
946      * @return the variable's value or <b>null</b> if the variable is unknown
947      */
948     protected String resolveVariable(final String variableName, final StrBuilder buf, final int startPos, final int endPos) {
949         final StrLookup<?> resolver = getVariableResolver();
950         if (resolver == null) {
951             return null;
952         }
953         return resolver.lookup(variableName);
954     }
955 
956     /**
957      * Returns the escape character.
958      *
959      * @return the character used for escaping variable references
960      */
961     public char getEscapeChar() {
962         return this.escapeChar;
963     }
964 
965     /**
966      * Sets the escape character.
967      * If this character is placed before a variable reference in the source
968      * text, this variable will be ignored.
969      *
970      * @param escapeCharacter  the escape character (0 for disabling escaping)
971      */
972     public void setEscapeChar(final char escapeCharacter) {
973         this.escapeChar = escapeCharacter;
974     }
975 
976     /**
977      * Gets the variable prefix matcher currently in use.
978      * <p>
979      * The variable prefix is the character or characters that identify the
980      * start of a variable. This prefix is expressed in terms of a matcher
981      * allowing advanced prefix matches.
982      * </p>
983      *
984      * @return the prefix matcher in use
985      */
986     public StrMatcher getVariablePrefixMatcher() {
987         return prefixMatcher;
988     }
989 
990     /**
991      * Sets the variable prefix matcher currently in use.
992      * <p>
993      * The variable prefix is the character or characters that identify the
994      * start of a variable. This prefix is expressed in terms of a matcher
995      * allowing advanced prefix matches.
996      * </p>
997      *
998      * @param prefixMatcher  the prefix matcher to use, null ignored
999      * @return this, to enable chaining
1000      * @throws NullPointerException if the prefix matcher is null
1001      */
1002     public StrSubstitutor setVariablePrefixMatcher(final StrMatcher prefixMatcher) {
1003         this.prefixMatcher = Objects.requireNonNull(prefixMatcher, "prefixMatcher");
1004         return this;
1005     }
1006 
1007     /**
1008      * Sets the variable prefix to use.
1009      * <p>
1010      * The variable prefix is the character or characters that identify the
1011      * start of a variable. This method allows a single character prefix to
1012      * be easily set.
1013      * </p>
1014      *
1015      * @param prefix  the prefix character to use
1016      * @return this, to enable chaining
1017      */
1018     public StrSubstitutor setVariablePrefix(final char prefix) {
1019         return setVariablePrefixMatcher(StrMatcher.charMatcher(prefix));
1020     }
1021 
1022     /**
1023      * Sets the variable prefix to use.
1024      * <p>
1025      * The variable prefix is the character or characters that identify the
1026      * start of a variable. This method allows a string prefix to be easily set.
1027      * </p>
1028      *
1029      * @param prefix  the prefix for variables, not null
1030      * @return this, to enable chaining
1031      * @throws NullPointerException if the prefix is null
1032      */
1033     public StrSubstitutor setVariablePrefix(final String prefix) {
1034         return setVariablePrefixMatcher(StrMatcher.stringMatcher(Objects.requireNonNull(prefix)));
1035     }
1036 
1037     /**
1038      * Gets the variable suffix matcher currently in use.
1039      * <p>
1040      * The variable suffix is the character or characters that identify the
1041      * end of a variable. This suffix is expressed in terms of a matcher
1042      * allowing advanced suffix matches.
1043      * </p>
1044      *
1045      * @return the suffix matcher in use
1046      */
1047     public StrMatcher getVariableSuffixMatcher() {
1048         return suffixMatcher;
1049     }
1050 
1051     /**
1052      * Sets the variable suffix matcher currently in use.
1053      * <p>
1054      * The variable suffix is the character or characters that identify the
1055      * end of a variable. This suffix is expressed in terms of a matcher
1056      * allowing advanced suffix matches.
1057      * </p>
1058      *
1059      * @param suffixMatcher  the suffix matcher to use, null ignored
1060      * @return this, to enable chaining
1061      * @throws NullPointerException if the suffix matcher is null
1062      */
1063     public StrSubstitutor setVariableSuffixMatcher(final StrMatcher suffixMatcher) {
1064         this.suffixMatcher = Objects.requireNonNull(suffixMatcher);
1065         return this;
1066     }
1067 
1068     /**
1069      * Sets the variable suffix to use.
1070      * <p>
1071      * The variable suffix is the character or characters that identify the
1072      * end of a variable. This method allows a single character suffix to
1073      * be easily set.
1074      * </p>
1075      *
1076      * @param suffix  the suffix character to use
1077      * @return this, to enable chaining
1078      */
1079     public StrSubstitutor setVariableSuffix(final char suffix) {
1080         return setVariableSuffixMatcher(StrMatcher.charMatcher(suffix));
1081     }
1082 
1083     /**
1084      * Sets the variable suffix to use.
1085      * <p>
1086      * The variable suffix is the character or characters that identify the
1087      * end of a variable. This method allows a string suffix to be easily set.
1088      * </p>
1089      *
1090      * @param suffix  the suffix for variables, not null
1091      * @return this, to enable chaining
1092      * @throws NullPointerException if the suffix is null
1093      */
1094     public StrSubstitutor setVariableSuffix(final String suffix) {
1095         return setVariableSuffixMatcher(StrMatcher.stringMatcher(Objects.requireNonNull(suffix)));
1096     }
1097 
1098     /**
1099      * Gets the variable default value delimiter matcher currently in use.
1100      * <p>
1101      * The variable default value delimiter is the character or characters that delimit the
1102      * variable name and the variable default value. This delimiter is expressed in terms of a matcher
1103      * allowing advanced variable default value delimiter matches.
1104      * </p>
1105      * <p>
1106      * If it returns null, then the variable default value resolution is disabled.
1107      * </p>
1108      *
1109      * @return the variable default value delimiter matcher in use, may be null
1110      * @since 3.2
1111      */
1112     public StrMatcher getValueDelimiterMatcher() {
1113         return valueDelimiterMatcher;
1114     }
1115 
1116     /**
1117      * Sets the variable default value delimiter matcher to use.
1118      * <p>
1119      * The variable default value delimiter is the character or characters that delimit the
1120      * variable name and the variable default value. This delimiter is expressed in terms of a matcher
1121      * allowing advanced variable default value delimiter matches.
1122      * </p>
1123      * <p>
1124      * If the {@code valueDelimiterMatcher} is null, then the variable default value resolution
1125      * becomes disabled.
1126      * </p>
1127      *
1128      * @param valueDelimiterMatcher  variable default value delimiter matcher to use, may be null
1129      * @return this, to enable chaining
1130      * @since 3.2
1131      */
1132     public StrSubstitutor setValueDelimiterMatcher(final StrMatcher valueDelimiterMatcher) {
1133         this.valueDelimiterMatcher = valueDelimiterMatcher;
1134         return this;
1135     }
1136 
1137     /**
1138      * Sets the variable default value delimiter to use.
1139      * <p>
1140      * The variable default value delimiter is the character or characters that delimit the
1141      * variable name and the variable default value. This method allows a single character
1142      * variable default value delimiter to be easily set.
1143      * </p>
1144      *
1145      * @param valueDelimiter  the variable default value delimiter character to use
1146      * @return this, to enable chaining
1147      * @since 3.2
1148      */
1149     public StrSubstitutor setValueDelimiter(final char valueDelimiter) {
1150         return setValueDelimiterMatcher(StrMatcher.charMatcher(valueDelimiter));
1151     }
1152 
1153     /**
1154      * Sets the variable default value delimiter to use.
1155      * <p>
1156      * The variable default value delimiter is the character or characters that delimit the
1157      * variable name and the variable default value. This method allows a string
1158      * variable default value delimiter to be easily set.
1159      * </p>
1160      * <p>
1161      * If the {@code valueDelimiter} is null or empty string, then the variable default
1162      * value resolution becomes disabled.
1163      * </p>
1164      *
1165      * @param valueDelimiter  the variable default value delimiter string to use, may be null or empty
1166      * @return this, to enable chaining
1167      * @since 3.2
1168      */
1169     public StrSubstitutor setValueDelimiter(final String valueDelimiter) {
1170         if (StringUtils.isEmpty(valueDelimiter)) {
1171             setValueDelimiterMatcher(null);
1172             return this;
1173         }
1174         return setValueDelimiterMatcher(StrMatcher.stringMatcher(valueDelimiter));
1175     }
1176 
1177     /**
1178      * Gets the VariableResolver that is used to lookup variables.
1179      *
1180      * @return the VariableResolver
1181      */
1182     public StrLookup<?> getVariableResolver() {
1183         return this.variableResolver;
1184     }
1185 
1186     /**
1187      * Sets the VariableResolver that is used to lookup variables.
1188      *
1189      * @param variableResolver  the VariableResolver
1190      */
1191     public void setVariableResolver(final StrLookup<?> variableResolver) {
1192         this.variableResolver = variableResolver;
1193     }
1194 
1195     /**
1196      * Returns a flag whether substitution is done in variable names.
1197      *
1198      * @return the substitution in variable names flag
1199      * @since 3.0
1200      */
1201     public boolean isEnableSubstitutionInVariables() {
1202         return enableSubstitutionInVariables;
1203     }
1204 
1205     /**
1206      * Sets a flag whether substitution is done in variable names. If set to
1207      * <b>true</b>, the names of variables can contain other variables which are
1208      * processed first before the original variable is evaluated, e.g.
1209      * {@code ${jre-${java.version}}}. The default value is <b>false</b>.
1210      *
1211      * @param enableSubstitutionInVariables the new value of the flag
1212      * @since 3.0
1213      */
1214     public void setEnableSubstitutionInVariables(
1215             final boolean enableSubstitutionInVariables) {
1216         this.enableSubstitutionInVariables = enableSubstitutionInVariables;
1217     }
1218 
1219     /**
1220      * Returns the flag controlling whether escapes are preserved during
1221      * substitution.
1222      *
1223      * @return the preserve escape flag
1224      * @since 3.5
1225      */
1226     public boolean isPreserveEscapes() {
1227         return preserveEscapes;
1228     }
1229 
1230     /**
1231      * Sets a flag controlling whether escapes are preserved during
1232      * substitution.  If set to <b>true</b>, the escape character is retained
1233      * during substitution (e.g. {@code $${this-is-escaped}} remains
1234      * {@code $${this-is-escaped}}).  If set to <b>false</b>, the escape
1235      * character is removed during substitution (e.g.
1236      * {@code $${this-is-escaped}} becomes
1237      * {@code ${this-is-escaped}}).  The default value is <b>false</b>
1238      *
1239      * @param preserveEscapes true if escapes are to be preserved
1240      * @since 3.5
1241      */
1242     public void setPreserveEscapes(final boolean preserveEscapes) {
1243         this.preserveEscapes = preserveEscapes;
1244     }
1245 }