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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      * Replaces all the occurrences of variables in the given source object with
171      * their matching values from the map.
172      *
173      * @param <V> the type of the values in the map
174      * @param source  the source text containing the variables to substitute, null returns null
175      * @param valueMap  the map with the values, may be null
176      * @return the result of the replace operation
177      */
178     public static <V> String replace(final Object source, final Map<String, V> valueMap) {
179         return new StrSubstitutor(valueMap).replace(source);
180     }
181     /**
182      * Replaces all the occurrences of variables in the given source object with
183      * their matching values from the map. This method allows to specify a
184      * custom variable prefix and suffix
185      *
186      * @param <V> the type of the values in the map
187      * @param source  the source text containing the variables to substitute, null returns null
188      * @param valueMap  the map with the values, may be null
189      * @param prefix  the prefix of variables, not null
190      * @param suffix  the suffix of variables, not null
191      * @return the result of the replace operation
192      * @throws IllegalArgumentException if the prefix or suffix is null
193      */
194     public static <V> String replace(final Object source, final Map<String, V> valueMap, final String prefix, final String suffix) {
195         return new StrSubstitutor(valueMap, prefix, suffix).replace(source);
196     }
197     /**
198      * Replaces all the occurrences of variables in the given source object with their matching
199      * values from the properties.
200      *
201      * @param source the source text containing the variables to substitute, null returns null
202      * @param valueProperties the properties with values, may be null
203      * @return the result of the replace operation
204      */
205     public static String replace(final Object source, final Properties valueProperties) {
206         if (valueProperties == null) {
207             return source.toString();
208         }
209         final Map<String, String> valueMap = new HashMap<>();
210         final Enumeration<?> propNames = valueProperties.propertyNames();
211         while (propNames.hasMoreElements()) {
212             final String propName = String.valueOf(propNames.nextElement());
213             final String propValue = valueProperties.getProperty(propName);
214             valueMap.put(propName, propValue);
215         }
216         return replace(source, valueMap);
217     }
218     /**
219      * Replaces all the occurrences of variables in the given source object with
220      * their matching values from the system properties.
221      *
222      * @param source  the source text containing the variables to substitute, null returns null
223      * @return the result of the replace operation
224      */
225     public static String replaceSystemProperties(final Object source) {
226         return new StrSubstitutor(StrLookup.systemPropertiesLookup()).replace(source);
227     }
228     /**
229      * Stores the escape character.
230      */
231     private char escapeChar;
232     /**
233      * Stores the variable prefix.
234      */
235     private StrMatcher prefixMatcher;
236     /**
237      * Stores the variable suffix.
238      */
239     private StrMatcher suffixMatcher;
240 
241     /**
242      * Stores the default variable value delimiter
243      */
244     private StrMatcher valueDelimiterMatcher;
245 
246     /**
247      * Variable resolution is delegated to an implementor of VariableResolver.
248      */
249     private StrLookup<?> variableResolver;
250 
251     /**
252      * The flag whether substitution in variable names is enabled.
253      */
254     private boolean enableSubstitutionInVariables;
255 
256     /**
257      * Whether escapes should be preserved.  Default is false;
258      */
259     private boolean preserveEscapes;
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      * Checks if the specified variable is already in the stack (list) of variables.
410      *
411      * @param varName  the variable name to check
412      * @param priorVariables  the list of prior variables
413      */
414     private void checkCyclicSubstitution(final String varName, final List<String> priorVariables) {
415         if (!priorVariables.contains(varName)) {
416             return;
417         }
418         final StrBuilder buf = new StrBuilder(256);
419         buf.append("Infinite loop in property interpolation of ");
420         buf.append(priorVariables.remove(0));
421         buf.append(": ");
422         buf.appendWithSeparators(priorVariables, "->");
423         throw new IllegalStateException(buf.toString());
424     }
425 
426     /**
427      * Returns the escape character.
428      *
429      * @return the character used for escaping variable references
430      */
431     public char getEscapeChar() {
432         return this.escapeChar;
433     }
434 
435     /**
436      * Gets the variable default value delimiter matcher currently in use.
437      * <p>
438      * The variable default value delimiter is the character or characters that delimit the
439      * variable name and the variable default value. This delimiter is expressed in terms of a matcher
440      * allowing advanced variable default value delimiter matches.
441      * </p>
442      * <p>
443      * If it returns null, then the variable default value resolution is disabled.
444      * </p>
445      *
446      * @return the variable default value delimiter matcher in use, may be null
447      * @since 3.2
448      */
449     public StrMatcher getValueDelimiterMatcher() {
450         return valueDelimiterMatcher;
451     }
452 
453     /**
454      * Gets the variable prefix matcher currently in use.
455      * <p>
456      * The variable prefix is the character or characters that identify the
457      * start of a variable. This prefix is expressed in terms of a matcher
458      * allowing advanced prefix matches.
459      * </p>
460      *
461      * @return the prefix matcher in use
462      */
463     public StrMatcher getVariablePrefixMatcher() {
464         return prefixMatcher;
465     }
466 
467     /**
468      * Gets the VariableResolver that is used to lookup variables.
469      *
470      * @return the VariableResolver
471      */
472     public StrLookup<?> getVariableResolver() {
473         return this.variableResolver;
474     }
475 
476     /**
477      * Gets the variable suffix matcher currently in use.
478      * <p>
479      * The variable suffix is the character or characters that identify the
480      * end of a variable. This suffix is expressed in terms of a matcher
481      * allowing advanced suffix matches.
482      * </p>
483      *
484      * @return the suffix matcher in use
485      */
486     public StrMatcher getVariableSuffixMatcher() {
487         return suffixMatcher;
488     }
489 
490     /**
491      * Returns a flag whether substitution is done in variable names.
492      *
493      * @return the substitution in variable names flag
494      * @since 3.0
495      */
496     public boolean isEnableSubstitutionInVariables() {
497         return enableSubstitutionInVariables;
498     }
499 
500     /**
501      * Returns the flag controlling whether escapes are preserved during
502      * substitution.
503      *
504      * @return the preserve escape flag
505      * @since 3.5
506      */
507     public boolean isPreserveEscapes() {
508         return preserveEscapes;
509     }
510 
511     /**
512      * Replaces all the occurrences of variables with their matching values
513      * from the resolver using the given source array as a template.
514      * The array is not altered by this method.
515      *
516      * @param source  the character array to replace in, not altered, null returns null
517      * @return the result of the replace operation
518      */
519     public String replace(final char[] source) {
520         if (source == null) {
521             return null;
522         }
523         final StrBuilder buf = new StrBuilder(source.length).append(source);
524         substitute(buf, 0, source.length);
525         return buf.toString();
526     }
527 
528     /**
529      * Replaces all the occurrences of variables with their matching values
530      * from the resolver using the given source array as a template.
531      * The array is not altered by this method.
532      * <p>
533      * Only the specified portion of the array will be processed.
534      * The rest of the array is not processed, and is not returned.
535      * </p>
536      *
537      * @param source  the character array to replace in, not altered, null returns null
538      * @param offset  the start offset within the array, must be valid
539      * @param length  the length within the array to be processed, must be valid
540      * @return the result of the replace operation
541      */
542     public String replace(final char[] source, final int offset, final int length) {
543         if (source == null) {
544             return null;
545         }
546         final StrBuilder buf = new StrBuilder(length).append(source, offset, length);
547         substitute(buf, 0, length);
548         return buf.toString();
549     }
550 
551     /**
552      * Replaces all the occurrences of variables with their matching values
553      * from the resolver using the given source as a template.
554      * The source is not altered by this method.
555      *
556      * @param source  the buffer to use as a template, not changed, null returns null
557      * @return the result of the replace operation
558      * @since 3.2
559      */
560     public String replace(final CharSequence source) {
561         if (source == null) {
562             return null;
563         }
564         return replace(source, 0, source.length());
565     }
566 
567     /**
568      * Replaces all the occurrences of variables with their matching values
569      * from the resolver using the given source as a template.
570      * The source is not altered by this method.
571      * <p>
572      * Only the specified portion of the buffer will be processed.
573      * The rest of the buffer is not processed, and is not returned.
574      * </p>
575      *
576      * @param source  the buffer to use as a template, not changed, null returns null
577      * @param offset  the start offset within the array, must be valid
578      * @param length  the length within the array to be processed, must be valid
579      * @return the result of the replace operation
580      * @since 3.2
581      */
582     public String replace(final CharSequence source, final int offset, final int length) {
583         if (source == null) {
584             return null;
585         }
586         final StrBuilder buf = new StrBuilder(length).append(source, offset, length);
587         substitute(buf, 0, length);
588         return buf.toString();
589     }
590 
591     /**
592      * Replaces all the occurrences of variables in the given source object with
593      * their matching values from the resolver. The input source object is
594      * converted to a string using {@code toString} and is not altered.
595      *
596      * @param source  the source to replace in, null returns null
597      * @return the result of the replace operation
598      */
599     public String replace(final Object source) {
600         if (source == null) {
601             return null;
602         }
603         final StrBuilder buf = new StrBuilder().append(source);
604         substitute(buf, 0, buf.length());
605         return buf.toString();
606     }
607 
608     /**
609      * Replaces all the occurrences of variables with their matching values
610      * from the resolver using the given source builder as a template.
611      * The builder is not altered by this method.
612      *
613      * @param source  the builder to use as a template, not changed, null returns null
614      * @return the result of the replace operation
615      */
616     public String replace(final StrBuilder source) {
617         if (source == null) {
618             return null;
619         }
620         final StrBuilder buf = new StrBuilder(source.length()).append(source);
621         substitute(buf, 0, buf.length());
622         return buf.toString();
623     }
624 
625     /**
626      * Replaces all the occurrences of variables with their matching values
627      * from the resolver using the given source builder as a template.
628      * The builder is not altered by this method.
629      * <p>
630      * Only the specified portion of the builder will be processed.
631      * The rest of the builder is not processed, and is not returned.
632      * </p>
633      *
634      * @param source  the builder to use as a template, not changed, null returns null
635      * @param offset  the start offset within the array, must be valid
636      * @param length  the length within the array to be processed, must be valid
637      * @return the result of the replace operation
638      */
639     public String replace(final StrBuilder source, final int offset, final int length) {
640         if (source == null) {
641             return null;
642         }
643         final StrBuilder buf = new StrBuilder(length).append(source, offset, length);
644         substitute(buf, 0, length);
645         return buf.toString();
646     }
647 
648     /**
649      * Replaces all the occurrences of variables with their matching values
650      * from the resolver using the given source string as a template.
651      *
652      * @param source  the string to replace in, null returns null
653      * @return the result of the replace operation
654      */
655     public String replace(final String source) {
656         if (source == null) {
657             return null;
658         }
659         final StrBuilder buf = new StrBuilder(source);
660         if (!substitute(buf, 0, source.length())) {
661             return source;
662         }
663         return buf.toString();
664     }
665 
666     /**
667      * Replaces all the occurrences of variables with their matching values
668      * from the resolver using the given source string as a template.
669      * <p>
670      * Only the specified portion of the string will be processed.
671      * The rest of the string is not processed, and is not returned.
672      * </p>
673      *
674      * @param source  the string to replace in, null returns null
675      * @param offset  the start offset within the array, must be valid
676      * @param length  the length within the array to be processed, must be valid
677      * @return the result of the replace operation
678      */
679     public String replace(final String source, final int offset, final int length) {
680         if (source == null) {
681             return null;
682         }
683         final StrBuilder buf = new StrBuilder(length).append(source, offset, length);
684         if (!substitute(buf, 0, length)) {
685             return source.substring(offset, offset + length);
686         }
687         return buf.toString();
688     }
689 
690     /**
691      * Replaces all the occurrences of variables with their matching values
692      * from the resolver using the given source buffer as a template.
693      * The buffer is not altered by this method.
694      *
695      * @param source  the buffer to use as a template, not changed, null returns null
696      * @return the result of the replace operation
697      */
698     public String replace(final StringBuffer source) {
699         if (source == null) {
700             return null;
701         }
702         final StrBuilder buf = new StrBuilder(source.length()).append(source);
703         substitute(buf, 0, buf.length());
704         return buf.toString();
705     }
706 
707     /**
708      * Replaces all the occurrences of variables with their matching values
709      * from the resolver using the given source buffer as a template.
710      * The buffer is not altered by this method.
711      * <p>
712      * Only the specified portion of the buffer will be processed.
713      * The rest of the buffer is not processed, and is not returned.
714      * </p>
715      *
716      * @param source  the buffer to use as a template, not changed, null returns null
717      * @param offset  the start offset within the array, must be valid
718      * @param length  the length within the array to be processed, must be valid
719      * @return the result of the replace operation
720      */
721     public String replace(final StringBuffer source, final int offset, final int length) {
722         if (source == null) {
723             return null;
724         }
725         final StrBuilder buf = new StrBuilder(length).append(source, offset, length);
726         substitute(buf, 0, length);
727         return buf.toString();
728     }
729 
730     /**
731      * Replaces all the occurrences of variables within the given source
732      * builder with their matching values from the resolver.
733      *
734      * @param source  the builder to replace in, updated, null returns zero
735      * @return true if altered
736      */
737     public boolean replaceIn(final StrBuilder source) {
738         if (source == null) {
739             return false;
740         }
741         return substitute(source, 0, source.length());
742     }
743 
744     /**
745      * Replaces all the occurrences of variables within the given source
746      * builder with their matching values from the resolver.
747      * <p>
748      * Only the specified portion of the builder will be processed.
749      * The rest of the builder is not processed, but it is not deleted.
750      * </p>
751      *
752      * @param source  the builder to replace in, null returns zero
753      * @param offset  the start offset within the array, must be valid
754      * @param length  the length within the builder to be processed, must be valid
755      * @return true if altered
756      */
757     public boolean replaceIn(final StrBuilder source, final int offset, final int length) {
758         if (source == null) {
759             return false;
760         }
761         return substitute(source, offset, length);
762     }
763 
764     /**
765      * Replaces all the occurrences of variables within the given source buffer
766      * with their matching values from the resolver.
767      * The buffer is updated with the result.
768      *
769      * @param source  the buffer to replace in, updated, null returns zero
770      * @return true if altered
771      */
772     public boolean replaceIn(final StringBuffer source) {
773         if (source == null) {
774             return false;
775         }
776         return replaceIn(source, 0, source.length());
777     }
778 
779     /**
780      * Replaces all the occurrences of variables within the given source buffer
781      * with their matching values from the resolver.
782      * The buffer is updated with the result.
783      * <p>
784      * Only the specified portion of the buffer will be processed.
785      * The rest of the buffer is not processed, but it is not deleted.
786      * </p>
787      *
788      * @param source  the buffer to replace in, updated, null returns zero
789      * @param offset  the start offset within the array, must be valid
790      * @param length  the length within the buffer to be processed, must be valid
791      * @return true if altered
792      */
793     public boolean replaceIn(final StringBuffer source, final int offset, final int length) {
794         if (source == null) {
795             return false;
796         }
797         final StrBuilder buf = new StrBuilder(length).append(source, offset, length);
798         if (!substitute(buf, 0, length)) {
799             return false;
800         }
801         source.replace(offset, offset + length, buf.toString());
802         return true;
803     }
804 
805     /**
806      * Replaces all the occurrences of variables within the given source buffer
807      * with their matching values from the resolver.
808      * The buffer is updated with the result.
809      *
810      * @param source  the buffer to replace in, updated, null returns zero
811      * @return true if altered
812      * @since 3.2
813      */
814     public boolean replaceIn(final StringBuilder source) {
815         if (source == null) {
816             return false;
817         }
818         return replaceIn(source, 0, source.length());
819     }
820 
821     /**
822      * Replaces all the occurrences of variables within the given source builder
823      * with their matching values from the resolver.
824      * The builder is updated with the result.
825      * <p>
826      * Only the specified portion of the buffer will be processed.
827      * The rest of the buffer is not processed, but it is not deleted.
828      * </p>
829      *
830      * @param source  the buffer to replace in, updated, null returns zero
831      * @param offset  the start offset within the array, must be valid
832      * @param length  the length within the buffer to be processed, must be valid
833      * @return true if altered
834      * @since 3.2
835      */
836     public boolean replaceIn(final StringBuilder source, final int offset, final int length) {
837         if (source == null) {
838             return false;
839         }
840         final StrBuilder buf = new StrBuilder(length).append(source, offset, length);
841         if (!substitute(buf, 0, length)) {
842             return false;
843         }
844         source.replace(offset, offset + length, buf.toString());
845         return true;
846     }
847 
848     /**
849      * Internal method that resolves the value of a variable.
850      * <p>
851      * Most users of this class do not need to call this method. This method is
852      * called automatically by the substitution process.
853      * </p>
854      * <p>
855      * Writers of subclasses can override this method if they need to alter
856      * how each substitution occurs. The method is passed the variable's name
857      * and must return the corresponding value. This implementation uses the
858      * {@link #getVariableResolver()} with the variable's name as the key.
859      * </p>
860      *
861      * @param variableName  the name of the variable, not null
862      * @param buf  the buffer where the substitution is occurring, not null
863      * @param startPos  the start position of the variable including the prefix, valid
864      * @param endPos  the end position of the variable including the suffix, valid
865      * @return the variable's value or <b>null</b> if the variable is unknown
866      */
867     protected String resolveVariable(final String variableName, final StrBuilder buf, final int startPos, final int endPos) {
868         final StrLookup<?> resolver = getVariableResolver();
869         if (resolver == null) {
870             return null;
871         }
872         return resolver.lookup(variableName);
873     }
874 
875     /**
876      * Sets a flag whether substitution is done in variable names. If set to
877      * <b>true</b>, the names of variables can contain other variables which are
878      * processed first before the original variable is evaluated, e.g.
879      * {@code ${jre-${java.version}}}. The default value is <b>false</b>.
880      *
881      * @param enableSubstitutionInVariables the new value of the flag
882      * @since 3.0
883      */
884     public void setEnableSubstitutionInVariables(
885             final boolean enableSubstitutionInVariables) {
886         this.enableSubstitutionInVariables = enableSubstitutionInVariables;
887     }
888 
889     /**
890      * Sets the escape character.
891      * If this character is placed before a variable reference in the source
892      * text, this variable will be ignored.
893      *
894      * @param escapeCharacter  the escape character (0 for disabling escaping)
895      */
896     public void setEscapeChar(final char escapeCharacter) {
897         this.escapeChar = escapeCharacter;
898     }
899 
900     /**
901      * Sets a flag controlling whether escapes are preserved during
902      * substitution.  If set to <b>true</b>, the escape character is retained
903      * during substitution (e.g. {@code $${this-is-escaped}} remains
904      * {@code $${this-is-escaped}}).  If set to <b>false</b>, the escape
905      * character is removed during substitution (e.g.
906      * {@code $${this-is-escaped}} becomes
907      * {@code ${this-is-escaped}}).  The default value is <b>false</b>
908      *
909      * @param preserveEscapes true if escapes are to be preserved
910      * @since 3.5
911      */
912     public void setPreserveEscapes(final boolean preserveEscapes) {
913         this.preserveEscapes = preserveEscapes;
914     }
915 
916     /**
917      * Sets the variable default value delimiter to use.
918      * <p>
919      * The variable default value delimiter is the character or characters that delimit the
920      * variable name and the variable default value. This method allows a single character
921      * variable default value delimiter to be easily set.
922      * </p>
923      *
924      * @param valueDelimiter  the variable default value delimiter character to use
925      * @return this, to enable chaining
926      * @since 3.2
927      */
928     public StrSubstitutor setValueDelimiter(final char valueDelimiter) {
929         return setValueDelimiterMatcher(StrMatcher.charMatcher(valueDelimiter));
930     }
931 
932     /**
933      * Sets the variable default value delimiter to use.
934      * <p>
935      * The variable default value delimiter is the character or characters that delimit the
936      * variable name and the variable default value. This method allows a string
937      * variable default value delimiter to be easily set.
938      * </p>
939      * <p>
940      * If the {@code valueDelimiter} is null or empty string, then the variable default
941      * value resolution becomes disabled.
942      * </p>
943      *
944      * @param valueDelimiter  the variable default value delimiter string to use, may be null or empty
945      * @return this, to enable chaining
946      * @since 3.2
947      */
948     public StrSubstitutor setValueDelimiter(final String valueDelimiter) {
949         if (StringUtils.isEmpty(valueDelimiter)) {
950             setValueDelimiterMatcher(null);
951             return this;
952         }
953         return setValueDelimiterMatcher(StrMatcher.stringMatcher(valueDelimiter));
954     }
955 
956     /**
957      * Sets the variable default value delimiter matcher to use.
958      * <p>
959      * The variable default value delimiter is the character or characters that delimit the
960      * variable name and the variable default value. This delimiter is expressed in terms of a matcher
961      * allowing advanced variable default value delimiter matches.
962      * </p>
963      * <p>
964      * If the {@code valueDelimiterMatcher} is null, then the variable default value resolution
965      * becomes disabled.
966      * </p>
967      *
968      * @param valueDelimiterMatcher  variable default value delimiter matcher to use, may be null
969      * @return this, to enable chaining
970      * @since 3.2
971      */
972     public StrSubstitutor setValueDelimiterMatcher(final StrMatcher valueDelimiterMatcher) {
973         this.valueDelimiterMatcher = valueDelimiterMatcher;
974         return this;
975     }
976 
977     /**
978      * Sets the variable prefix to use.
979      * <p>
980      * The variable prefix is the character or characters that identify the
981      * start of a variable. This method allows a single character prefix to
982      * be easily set.
983      * </p>
984      *
985      * @param prefix  the prefix character to use
986      * @return this, to enable chaining
987      */
988     public StrSubstitutor setVariablePrefix(final char prefix) {
989         return setVariablePrefixMatcher(StrMatcher.charMatcher(prefix));
990     }
991 
992     /**
993      * Sets the variable prefix to use.
994      * <p>
995      * The variable prefix is the character or characters that identify the
996      * start of a variable. This method allows a string prefix to be easily set.
997      * </p>
998      *
999      * @param prefix  the prefix for variables, not null
1000      * @return this, to enable chaining
1001      * @throws NullPointerException if the prefix is null
1002      */
1003     public StrSubstitutor setVariablePrefix(final String prefix) {
1004         return setVariablePrefixMatcher(StrMatcher.stringMatcher(Objects.requireNonNull(prefix)));
1005     }
1006 
1007     /**
1008      * Sets the variable prefix matcher currently in use.
1009      * <p>
1010      * The variable prefix is the character or characters that identify the
1011      * start of a variable. This prefix is expressed in terms of a matcher
1012      * allowing advanced prefix matches.
1013      * </p>
1014      *
1015      * @param prefixMatcher  the prefix matcher to use, null ignored
1016      * @return this, to enable chaining
1017      * @throws NullPointerException if the prefix matcher is null
1018      */
1019     public StrSubstitutor setVariablePrefixMatcher(final StrMatcher prefixMatcher) {
1020         this.prefixMatcher = Objects.requireNonNull(prefixMatcher, "prefixMatcher");
1021         return this;
1022     }
1023 
1024     /**
1025      * Sets the VariableResolver that is used to lookup variables.
1026      *
1027      * @param variableResolver  the VariableResolver
1028      */
1029     public void setVariableResolver(final StrLookup<?> variableResolver) {
1030         this.variableResolver = variableResolver;
1031     }
1032 
1033     /**
1034      * Sets the variable suffix to use.
1035      * <p>
1036      * The variable suffix is the character or characters that identify the
1037      * end of a variable. This method allows a single character suffix to
1038      * be easily set.
1039      * </p>
1040      *
1041      * @param suffix  the suffix character to use
1042      * @return this, to enable chaining
1043      */
1044     public StrSubstitutor setVariableSuffix(final char suffix) {
1045         return setVariableSuffixMatcher(StrMatcher.charMatcher(suffix));
1046     }
1047 
1048     /**
1049      * Sets the variable suffix to use.
1050      * <p>
1051      * The variable suffix is the character or characters that identify the
1052      * end of a variable. This method allows a string suffix to be easily set.
1053      * </p>
1054      *
1055      * @param suffix  the suffix for variables, not null
1056      * @return this, to enable chaining
1057      * @throws NullPointerException if the suffix is null
1058      */
1059     public StrSubstitutor setVariableSuffix(final String suffix) {
1060         return setVariableSuffixMatcher(StrMatcher.stringMatcher(Objects.requireNonNull(suffix)));
1061     }
1062 
1063     /**
1064      * Sets the variable suffix matcher currently in use.
1065      * <p>
1066      * The variable suffix is the character or characters that identify the
1067      * end of a variable. This suffix is expressed in terms of a matcher
1068      * allowing advanced suffix matches.
1069      * </p>
1070      *
1071      * @param suffixMatcher  the suffix matcher to use, null ignored
1072      * @return this, to enable chaining
1073      * @throws NullPointerException if the suffix matcher is null
1074      */
1075     public StrSubstitutor setVariableSuffixMatcher(final StrMatcher suffixMatcher) {
1076         this.suffixMatcher = Objects.requireNonNull(suffixMatcher);
1077         return this;
1078     }
1079 
1080     /**
1081      * Internal method that substitutes the variables.
1082      * <p>
1083      * Most users of this class do not need to call this method. This method will
1084      * be called automatically by another (public) method.
1085      * </p>
1086      * <p>
1087      * Writers of subclasses can override this method if they need access to
1088      * the substitution process at the start or end.
1089      * </p>
1090      *
1091      * @param buf  the string builder to substitute into, not null
1092      * @param offset  the start offset within the builder, must be valid
1093      * @param length  the length within the builder to be processed, must be valid
1094      * @return true if altered
1095      */
1096     protected boolean substitute(final StrBuilder buf, final int offset, final int length) {
1097         return substitute(buf, offset, length, null) > 0;
1098     }
1099 
1100     /**
1101      * Recursive handler for multiple levels of interpolation. This is the main
1102      * interpolation method, which resolves the values of all variable references
1103      * contained in the passed-in text.
1104      *
1105      * @param buf  the string builder to substitute into, not null
1106      * @param offset  the start offset within the builder, must be valid
1107      * @param length  the length within the builder to be processed, must be valid
1108      * @param priorVariables  the stack keeping track of the replaced variables, may be null
1109      * @return the length change that occurs, unless priorVariables is null when the int
1110      *  represents a boolean flag as to whether any change occurred.
1111      */
1112     private int substitute(final StrBuilder buf, final int offset, final int length, List<String> priorVariables) {
1113         final StrMatcher pfxMatcher = getVariablePrefixMatcher();
1114         final StrMatcher suffMatcher = getVariableSuffixMatcher();
1115         final char escape = getEscapeChar();
1116         final StrMatcher valueDelimMatcher = getValueDelimiterMatcher();
1117         final boolean substitutionInVariablesEnabled = isEnableSubstitutionInVariables();
1118 
1119         final boolean top = priorVariables == null;
1120         boolean altered = false;
1121         int lengthChange = 0;
1122         char[] chars = buf.buffer;
1123         int bufEnd = offset + length;
1124         int pos = offset;
1125         while (pos < bufEnd) {
1126             final int startMatchLen = pfxMatcher.isMatch(chars, pos, offset,
1127                     bufEnd);
1128             if (startMatchLen == 0) {
1129                 pos++;
1130             } else // found variable start marker
1131             if (pos > offset && chars[pos - 1] == escape) {
1132                 // escaped
1133                 if (preserveEscapes) {
1134                     pos++;
1135                     continue;
1136                 }
1137                 buf.deleteCharAt(pos - 1);
1138                 chars = buf.buffer; // in case buffer was altered
1139                 lengthChange--;
1140                 altered = true;
1141                 bufEnd--;
1142             } else {
1143                 // find suffix
1144                 final int startPos = pos;
1145                 pos += startMatchLen;
1146                 int endMatchLen;
1147                 int nestedVarCount = 0;
1148                 while (pos < bufEnd) {
1149                     if (substitutionInVariablesEnabled
1150                             && (endMatchLen = pfxMatcher.isMatch(chars,
1151                                     pos, offset, bufEnd)) != 0) {
1152                         // found a nested variable start
1153                         nestedVarCount++;
1154                         pos += endMatchLen;
1155                         continue;
1156                     }
1157 
1158                     endMatchLen = suffMatcher.isMatch(chars, pos, offset,
1159                             bufEnd);
1160                     if (endMatchLen == 0) {
1161                         pos++;
1162                     } else {
1163                         // found variable end marker
1164                         if (nestedVarCount == 0) {
1165                             String varNameExpr = new String(chars, startPos
1166                                     + startMatchLen, pos - startPos
1167                                     - startMatchLen);
1168                             if (substitutionInVariablesEnabled) {
1169                                 final StrBuilder bufName = new StrBuilder(varNameExpr);
1170                                 substitute(bufName, 0, bufName.length());
1171                                 varNameExpr = bufName.toString();
1172                             }
1173                             pos += endMatchLen;
1174                             final int endPos = pos;
1175 
1176                             String varName = varNameExpr;
1177                             String varDefaultValue = null;
1178 
1179                             if (valueDelimMatcher != null) {
1180                                 final char [] varNameExprChars = varNameExpr.toCharArray();
1181                                 int valueDelimiterMatchLen;
1182                                 for (int i = 0; i < varNameExprChars.length; i++) {
1183                                     // if there's any nested variable when nested variable substitution disabled, then stop resolving name and default value.
1184                                     if (!substitutionInVariablesEnabled
1185                                             && pfxMatcher.isMatch(varNameExprChars, i, i, varNameExprChars.length) != 0) {
1186                                         break;
1187                                     }
1188                                     if ((valueDelimiterMatchLen = valueDelimMatcher.isMatch(varNameExprChars, i)) != 0) {
1189                                         varName = varNameExpr.substring(0, i);
1190                                         varDefaultValue = varNameExpr.substring(i + valueDelimiterMatchLen);
1191                                         break;
1192                                     }
1193                                 }
1194                             }
1195 
1196                             // on the first call initialize priorVariables
1197                             if (priorVariables == null) {
1198                                 priorVariables = new ArrayList<>();
1199                                 priorVariables.add(new String(chars,
1200                                         offset, length));
1201                             }
1202 
1203                             // handle cyclic substitution
1204                             checkCyclicSubstitution(varName, priorVariables);
1205                             priorVariables.add(varName);
1206 
1207                             // resolve the variable
1208                             String varValue = resolveVariable(varName, buf,
1209                                     startPos, endPos);
1210                             if (varValue == null) {
1211                                 varValue = varDefaultValue;
1212                             }
1213                             if (varValue != null) {
1214                                 // recursive replace
1215                                 final int varLen = varValue.length();
1216                                 buf.replace(startPos, endPos, varValue);
1217                                 altered = true;
1218                                 int change = substitute(buf, startPos,
1219                                         varLen, priorVariables);
1220                                 change = change
1221                                         + varLen - (endPos - startPos);
1222                                 pos += change;
1223                                 bufEnd += change;
1224                                 lengthChange += change;
1225                                 chars = buf.buffer; // in case buffer was
1226                                                     // altered
1227                             }
1228 
1229                             // remove variable from the cyclic stack
1230                             priorVariables
1231                                     .remove(priorVariables.size() - 1);
1232                             break;
1233                         }
1234                         nestedVarCount--;
1235                         pos += endMatchLen;
1236                     }
1237                 }
1238             }
1239         }
1240         if (top) {
1241             return altered ? 1 : 0;
1242         }
1243         return lengthChange;
1244     }
1245 }