    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.text;
    018
    019import java.util.ArrayList;
    020import java.util.Enumeration;
    021import java.util.HashMap;
    022import java.util.List;
    023import java.util.Map;
    024import java.util.Properties;
    025
    026import org.apache.commons.lang3.Validate;
    027import org.apache.commons.text.lookup.StringLookup;
    028import org.apache.commons.text.lookup.StringLookupFactory;
    029import org.apache.commons.text.matcher.StringMatcher;
    030import org.apache.commons.text.matcher.StringMatcherFactory;
    031
    032/**
    033 * Substitutes variables within a string by values.
    034 * <p>
    035 * This class takes a piece of text and substitutes all the variables within it. The default definition of a variable is
    036 * <code>${variableName}</code>. The prefix and suffix can be changed via constructors and set methods.
    037 * <p>
    038 * Variable values are typically resolved from a map, but could also be resolved from system properties, or by supplying
    039 * a custom variable resolver.
    040 * <p>
    041 * The simplest example is to use this class to replace Java System properties. For example:
    042 *
    043 * <pre>
    044 * StrSubstitutor
    045 *         .replaceSystemProperties("You are running with java.version = ${java.version} and os.name = ${os.name}.");
    046 * </pre>
    047 * <p>
    048 * Typical usage of this class follows the following pattern: First an instance is created and initialized with the map
    049 * that contains the values for the available variables. If a prefix and/or suffix for variables should be used other
    050 * than the default ones, the appropriate settings can be performed. After that the <code>replace()</code> method can be
    051 * called passing in the source text for interpolation. In the returned text all variable references (as long as their
    052 * values are known) will be resolved. The following example demonstrates this:
    053 *
    054 * <pre>
    055 * Map valuesMap = HashMap();
    056 * valuesMap.put(&quot;animal&quot;, &quot;quick brown fox&quot;);
    057 * valuesMap.put(&quot;target&quot;, &quot;lazy dog&quot;);
    058 * String templateString = &quot;The ${animal} jumped over the ${target}.&quot;;
    059 * StrSubstitutor sub = new StrSubstitutor(valuesMap);
    060 * String resolvedString = sub.replace(templateString);
    061 * </pre>
    062 *
    063 * yielding:
    064 *
    065 * <pre>
    066 *      The quick brown fox jumped over the lazy dog.
    067 * </pre>
    068 * <p>
    069 * Also, this class allows to set a default value for unresolved variables. The default value for a variable can be
    070 * appended to the variable name after the variable default value delimiter. The default value of the variable default
    071 * value delimiter is ':-', as in bash and other *nix shells, as those are arguably where the default ${} delimiter set
    072 * originated. The variable default value delimiter can be manually set by calling
    073 * {@link #setValueDelimiterMatcher(StringMatcher)}, {@link #setValueDelimiter(char)} or
    074 * {@link #setValueDelimiter(String)}. The following shows an example with variable default value settings:
    075 *
    076 * <pre>
    077 * Map valuesMap = HashMap();
    078 * valuesMap.put(&quot;animal&quot;, &quot;quick brown fox&quot;);
    079 * valuesMap.put(&quot;target&quot;, &quot;lazy dog&quot;);
    080 * String templateString = &quot;The ${animal} jumped over the ${target}. ${undefined.number:-1234567890}.&quot;;
    081 * StrSubstitutor sub = new StrSubstitutor(valuesMap);
    082 * String resolvedString = sub.replace(templateString);
    083 * </pre>
    084 *
    085 * yielding:
    086 *
    087 * <pre>
    088 *      The quick brown fox jumped over the lazy dog. 1234567890.
    089 * </pre>
    090 * <p>
    091 * In addition to this usage pattern there are some static convenience methods that cover the most common use cases.
    092 * These methods can be used without the need of manually creating an instance. However if multiple replace operations
    093 * are to be performed, creating and reusing an instance of this class will be more efficient.
    094 * <p>
    095 * Variable replacement works in a recursive way. Thus, if a variable value contains a variable then that variable will
    096 * also be replaced. Cyclic replacements are detected and will cause an exception to be thrown.
    097 * <p>
    098 * Sometimes the interpolation's result must contain a variable prefix. As an example take the following source text:
    099 *
    100 * <pre>
    101 *   The variable ${${name}} must be used.
    102 * </pre>
    103 *
    104 * Here only the variable's name referred to in the text should be replaced resulting in the text (assuming that the
    105 * value of the <code>name</code> variable is <code>x</code>):
    106 *
    107 * <pre>
    108 *   The variable ${x} must be used.
    109 * </pre>
    110 *
    111 * To achieve this effect there are two possibilities: Either set a different prefix and suffix for variables which do
    112 * not conflict with the result text you want to produce. The other possibility is to use the escape character, by
    113 * default '$'. If this character is placed before a variable reference, this reference is ignored and won't be
    114 * replaced. For example:
    115 *
    116 * <pre>
    117 *   The variable $${${name}} must be used.
    118 * </pre>
    119 * <p>
    120 * In some complex scenarios you might even want to perform substitution in the names of variables, for instance
    121 *
    122 * <pre>
    123 * ${jre-${java.specification.version}}
    124 * </pre>
    125 *
    126 * <code>StrSubstitutor</code> supports this recursive substitution in variable names, but it has to be enabled
    127 * explicitly by setting the {@link #setEnableSubstitutionInVariables(boolean) enableSubstitutionInVariables} property
    128 * to <b>true</b>.
    129 * <p>
    130 * This class is <b>not</b> thread safe.
    131 * </p>
    132 *
    133 * @since 1.3
    134 */
    135public class StringSubstitutor {
    136
    137    /**
    138     * Constant for the default escape character.
    139     */
    140    public static final char DEFAULT_ESCAPE = '$';
    141
    142    /**
    143     * Constant for the default variable prefix.
    144     */
    145    public static final StringMatcher DEFAULT_PREFIX = StringMatcherFactory.INSTANCE.stringMatcher("${");
    146
    147    /**
    148     * Constant for the default variable suffix.
    149     */
    150    public static final StringMatcher DEFAULT_SUFFIX = StringMatcherFactory.INSTANCE.stringMatcher("}");
    151
    152    /**
    153     * Constant for the default value delimiter of a variable.
    154     */
    155    public static final StringMatcher DEFAULT_VALUE_DELIMITER = StringMatcherFactory.INSTANCE.stringMatcher(":-");
    156
    157    // -----------------------------------------------------------------------
    158    /**
    159     * Replaces all the occurrences of variables in the given source object with their matching values from the map.
    160     *
    161     * @param <V>
    162     *            the type of the values in the map
    163     * @param source
    164     *            the source text containing the variables to substitute, null returns null
    165     * @param valueMap
    166     *            the map with the values, may be null
    167     * @return the result of the replace operation
    168     */
    169    public static <V> String replace(final Object source, final Map<String, V> valueMap) {
    170        return new StringSubstitutor(valueMap).replace(source);
    171    }
    172
    173    /**
    174     * Replaces all the occurrences of variables in the given source object with their matching values from the map.
    175     * This method allows to specify a custom variable prefix and suffix
    176     *
    177     * @param <V>
    178     *            the type of the values in the map
    179     * @param source
    180     *            the source text containing the variables to substitute, null returns null
    181     * @param valueMap
    182     *            the map with the values, may be null
    183     * @param prefix
    184     *            the prefix of variables, not null
    185     * @param suffix
    186     *            the suffix of variables, not null
    187     * @return the result of the replace operation
    188     * @throws IllegalArgumentException
    189     *             if the prefix or suffix is null
    190     */
    191    public static <V> String replace(final Object source, final Map<String, V> valueMap, final String prefix,
    192            final String suffix) {
    193        return new StringSubstitutor(valueMap, prefix, suffix).replace(source);
    194    }
    195
    196    /**
    197     * Replaces all the occurrences of variables in the given source object with their matching values from the
    198     * properties.
    199     *
    200     * @param source
    201     *            the source text containing the variables to substitute, null returns null
    202     * @param valueProperties
    203     *            the properties with values, may be null
    204     * @return the result of the replace operation
    205     */
    206    public static String replace(final Object source, final Properties valueProperties) {
    207        if (valueProperties == null) {
    208            return source.toString();
    209        }
    210        final Map<String, String> valueMap = new HashMap<>();
    211        final Enumeration<?> propNames = valueProperties.propertyNames();
    212        while (propNames.hasMoreElements()) {
    213            final String propName = (String) propNames.nextElement();
    214            final String propValue = valueProperties.getProperty(propName);
    215            valueMap.put(propName, propValue);
    216        }
    217        return StringSubstitutor.replace(source, valueMap);
    218    }
    219
    220    /**
    221     * Replaces all the occurrences of variables in the given source object with their matching values from the system
    222     * properties.
    223     *
    224     * @param source
    225     *            the source text containing the variables to substitute, null returns null
    226     * @return the result of the replace operation
    227     */
    228    public static String replaceSystemProperties(final Object source) {
    229        return new StringSubstitutor(StringLookupFactory.INSTANCE.systemPropertyStringLookup()).replace(source);
    230    }
    231
    232    /**
    233     * Stores the escape character.
    234     */
    235    private char escapeChar;
    236
    237    /**
    238     * Stores the variable prefix.
    239     */
    240    private StringMatcher prefixMatcher;
    241
    242    /**
    243     * Stores the variable suffix.
    244     */
    245    private StringMatcher suffixMatcher;
    246
    247    /**
    248     * Stores the default variable value delimiter.
    249     */
    250    private StringMatcher valueDelimiterMatcher;
    251
    252    /**
    253     * Variable resolution is delegated to an implementor of {@link StringLookup}.
    254     */
    255    private StringLookup variableResolver;
    256
    257    /**
    258     * The flag whether substitution in variable names is enabled.
    259     */
    260    private boolean enableSubstitutionInVariables;
    261
    262    /**
    263     * Whether escapes should be preserved. Default is false;
    264     */
    265    private boolean preserveEscapes = false;
    266
    267    /**
    268     * The flag whether substitution in variable values is disabled.
    269     */
    270    private boolean disableSubstitutionInValues;
    271
    272    // -----------------------------------------------------------------------
    273    /**
    274     * Creates a new instance with defaults for variable prefix and suffix and the escaping character.
    275     */
    276    public StringSubstitutor() {
    277        this((StringLookup) null, DEFAULT_PREFIX, DEFAULT_SUFFIX, DEFAULT_ESCAPE);
    278    }
    279
    280    /**
    281     * Creates a new instance and initializes it. Uses defaults for variable prefix and suffix and the escaping
    282     * character.
    283     *
    284     * @param <V>
    285     *            the type of the values in the map
    286     * @param valueMap
    287     *            the map with the variables' values, may be null
    288     */
    289    public <V> StringSubstitutor(final Map<String, V> valueMap) {
    290        this(StringLookupFactory.INSTANCE.mapStringLookup(valueMap), DEFAULT_PREFIX, DEFAULT_SUFFIX, DEFAULT_ESCAPE);
    291    }
    292
    293    /**
    294     * Creates a new instance and initializes it. Uses a default escaping character.
    295     *
    296     * @param <V>
    297     *            the type of the values in the map
    298     * @param valueMap
    299     *            the map with the variables' values, may be null
    300     * @param prefix
    301     *            the prefix for variables, not null
    302     * @param suffix
    303     *            the suffix for variables, not null
    304     * @throws IllegalArgumentException
    305     *             if the prefix or suffix is null
    306     */
    307    public <V> StringSubstitutor(final Map<String, V> valueMap, final String prefix, final String suffix) {
    308        this(StringLookupFactory.INSTANCE.mapStringLookup(valueMap), prefix, suffix, DEFAULT_ESCAPE);
    309    }
    310
    311    /**
    312     * Creates a new instance and initializes it.
    313     *
    314     * @param <V>
    315     *            the type of the values in the map
    316     * @param valueMap
    317     *            the map with the variables' values, may be null
    318     * @param prefix
    319     *            the prefix for variables, not null
    320     * @param suffix
    321     *            the suffix for variables, not null
    322     * @param escape
    323     *            the escape character
    324     * @throws IllegalArgumentException
    325     *             if the prefix or suffix is null
    326     */
    327    public <V> StringSubstitutor(final Map<String, V> valueMap, final String prefix, final String suffix,
    328            final char escape) {
    329        this(StringLookupFactory.INSTANCE.mapStringLookup(valueMap), prefix, suffix, escape);
    330    }
    331
    332    /**
    333     * Creates a new instance and initializes it.
    334     *
    335     * @param <V>
    336     *            the type of the values in the map
    337     * @param valueMap
    338     *            the map with the variables' values, may be null
    339     * @param prefix
    340     *            the prefix for variables, not null
    341     * @param suffix
    342     *            the suffix for variables, not null
    343     * @param escape
    344     *            the escape character
    345     * @param valueDelimiter
    346     *            the variable default value delimiter, may be null
    347     * @throws IllegalArgumentException
    348     *             if the prefix or suffix is null
    349     */
    350    public <V> StringSubstitutor(final Map<String, V> valueMap, final String prefix, final String suffix,
    351            final char escape, final String valueDelimiter) {
    352        this(StringLookupFactory.INSTANCE.mapStringLookup(valueMap), prefix, suffix, escape, valueDelimiter);
    353    }
    354
    355    /**
    356     * Creates a new instance and initializes it.
    357     *
    358     * @param variableResolver
    359     *            the variable resolver, may be null
    360     */
    361    public StringSubstitutor(final StringLookup variableResolver) {
    362        this(variableResolver, DEFAULT_PREFIX, DEFAULT_SUFFIX, DEFAULT_ESCAPE);
    363    }
    364
    365    /**
    366     * Creates a new instance and initializes it.
    367     *
    368     * @param variableResolver
    369     *            the variable resolver, may be null
    370     * @param prefix
    371     *            the prefix for variables, not null
    372     * @param suffix
    373     *            the suffix for variables, not null
    374     * @param escape
    375     *            the escape character
    376     * @throws IllegalArgumentException
    377     *             if the prefix or suffix is null
    378     */
    379    public StringSubstitutor(final StringLookup variableResolver, final String prefix, final String suffix,
    380            final char escape) {
    381        this.setVariableResolver(variableResolver);
    382        this.setVariablePrefix(prefix);
    383        this.setVariableSuffix(suffix);
    384        this.setEscapeChar(escape);
    385        this.setValueDelimiterMatcher(DEFAULT_VALUE_DELIMITER);
    386    }
    387
    388    /**
    389     * Creates a new instance and initializes it.
    390     *
    391     * @param variableResolver
    392     *            the variable resolver, may be null
    393     * @param prefix
    394     *            the prefix for variables, not null
    395     * @param suffix
    396     *            the suffix for variables, not null
    397     * @param escape
    398     *            the escape character
    399     * @param valueDelimiter
    400     *            the variable default value delimiter string, may be null
    401     * @throws IllegalArgumentException
    402     *             if the prefix or suffix is null
    403     */
    404    public StringSubstitutor(final StringLookup variableResolver, final String prefix, final String suffix,
    405            final char escape, final String valueDelimiter) {
    406        this.setVariableResolver(variableResolver);
    407        this.setVariablePrefix(prefix);
    408        this.setVariableSuffix(suffix);
    409        this.setEscapeChar(escape);
    410        this.setValueDelimiter(valueDelimiter);
    411    }
    412
    413    /**
    414     * Creates a new instance and initializes it.
    415     *
    416     * @param variableResolver
    417     *            the variable resolver, may be null
    418     * @param prefixMatcher
    419     *            the prefix for variables, not null
    420     * @param suffixMatcher
    421     *            the suffix for variables, not null
    422     * @param escape
    423     *            the escape character
    424     * @throws IllegalArgumentException
    425     *             if the prefix or suffix is null
    426     */
    427    public StringSubstitutor(final StringLookup variableResolver, final StringMatcher prefixMatcher,
    428            final StringMatcher suffixMatcher, final char escape) {
    429        this(variableResolver, prefixMatcher, suffixMatcher, escape, DEFAULT_VALUE_DELIMITER);
    430    }
    431
    432    /**
    433     * Creates a new instance and initializes it.
    434     *
    435     * @param variableResolver
    436     *            the variable resolver, may be null
    437     * @param prefixMatcher
    438     *            the prefix for variables, not null
    439     * @param suffixMatcher
    440     *            the suffix for variables, not null
    441     * @param escape
    442     *            the escape character
    443     * @param valueDelimiterMatcher
    444     *            the variable default value delimiter matcher, may be null
    445     * @throws IllegalArgumentException
    446     *             if the prefix or suffix is null
    447     */
    448    public StringSubstitutor(final StringLookup variableResolver, final StringMatcher prefixMatcher,
    449            final StringMatcher suffixMatcher, final char escape, final StringMatcher valueDelimiterMatcher) {
    450        this.setVariableResolver(variableResolver);
    451        this.setVariablePrefixMatcher(prefixMatcher);
    452        this.setVariableSuffixMatcher(suffixMatcher);
    453        this.setEscapeChar(escape);
    454        this.setValueDelimiterMatcher(valueDelimiterMatcher);
    455    }
    456
    457    /**
    458     * Checks if the specified variable is already in the stack (list) of variables.
    459     *
    460     * @param varName
    461     *            the variable name to check
    462     * @param priorVariables
    463     *            the list of prior variables
    464     */
    465    private void checkCyclicSubstitution(final String varName, final List<String> priorVariables) {
    466        if (!priorVariables.contains(varName)) {
    467            return;
    468        }
    469        final TextStringBuilder buf = new TextStringBuilder(256);
    470        buf.append("Infinite loop in property interpolation of ");
    471        buf.append(priorVariables.remove(0));
    472        buf.append(": ");
    473        buf.appendWithSeparators(priorVariables, "->");
    474        throw new IllegalStateException(buf.toString());
    475    }
    476
    477    // Escape
    478    // -----------------------------------------------------------------------
    479    /**
    480     * Returns the escape character.
    481     *
    482     * @return the character used for escaping variable references
    483     */
    484    public char getEscapeChar() {
    485        return this.escapeChar;
    486    }
    487
    488    // Resolver
    489    // -----------------------------------------------------------------------
    490    /**
    491     * Gets the StringLookup that is used to lookup variables.
    492     *
    493     * @return the StringLookup
    494     */
    495    public StringLookup getStringLookup() {
    496        return this.variableResolver;
    497    }
    498
    499    // Variable Default Value Delimiter
    500    // -----------------------------------------------------------------------
    501    /**
    502     * Gets the variable default value delimiter matcher currently in use.
    503     * <p>
    504     * The variable default value delimiter is the character or characters that delimite the variable name and the
    505     * variable default value. This delimiter is expressed in terms of a matcher allowing advanced variable default
    506     * value delimiter matches.
    507     * <p>
    508     * If it returns null, then the variable default value resolution is disabled.
    509     *
    510     * @return the variable default value delimiter matcher in use, may be null
    511     */
    512    public StringMatcher getValueDelimiterMatcher() {
    513        return valueDelimiterMatcher;
    514    }
    515
    516    // Prefix
    517    // -----------------------------------------------------------------------
    518    /**
    519     * Gets the variable prefix matcher currently in use.
    520     * <p>
    521     * The variable prefix is the character or characters that identify the start of a variable. This prefix is
    522     * expressed in terms of a matcher allowing advanced prefix matches.
    523     *
    524     * @return the prefix matcher in use
    525     */
    526    public StringMatcher getVariablePrefixMatcher() {
    527        return prefixMatcher;
    528    }
    529
    530    // Suffix
    531    // -----------------------------------------------------------------------
    532    /**
    533     * Gets the variable suffix matcher currently in use.
    534     * <p>
    535     * The variable suffix is the character or characters that identify the end of a variable. This suffix is expressed
    536     * in terms of a matcher allowing advanced suffix matches.
    537     *
    538     * @return the suffix matcher in use
    539     */
    540    public StringMatcher getVariableSuffixMatcher() {
    541        return suffixMatcher;
    542    }
    543
    544    /**
    545     * Returns a flag whether substitution is disabled in variable values.If set to <b>true</b>, the values of variables
    546     * can contain other variables will not be processed and substituted original variable is evaluated, e.g.
    547     *
    548     * <pre>
    549     * Map valuesMap = HashMap();
    550     * valuesMap.put(&quot;name&quot;, &quot;Douglas ${surname}&quot;);
    551     * valuesMap.put(&quot;surname&quot;, &quot;Crockford&quot;);
    552     * String templateString = &quot;Hi ${name}&quot;;
    553     * StrSubstitutor sub = new StrSubstitutor(valuesMap);
    554     * String resolvedString = sub.replace(templateString);
    555     * </pre>
    556     *
    557     * yielding:
    558     *
    559     * <pre>
    560     *      Hi Douglas ${surname}
    561     * </pre>
    562     *
    563     * @return the substitution in variable values flag
    564     */
    565    public boolean isDisableSubstitutionInValues() {
    566        return disableSubstitutionInValues;
    567    }
    568
    569    // Substitution support in variable names
    570    // -----------------------------------------------------------------------
    571    /**
    572     * Returns a flag whether substitution is done in variable names.
    573     *
    574     * @return the substitution in variable names flag
    575     */
    576    public boolean isEnableSubstitutionInVariables() {
    577        return enableSubstitutionInVariables;
    578    }
    579
    580    /**
    581     * Returns the flag controlling whether escapes are preserved during substitution.
    582     *
    583     * @return the preserve escape flag
    584     */
    585    public boolean isPreserveEscapes() {
    586        return preserveEscapes;
    587    }
    588
    589    // -----------------------------------------------------------------------
    590    /**
    591     * Replaces all the occurrences of variables with their matching values from the resolver using the given source
    592     * array as a template. The array is not altered by this method.
    593     *
    594     * @param source
    595     *            the character array to replace in, not altered, null returns null
    596     * @return the result of the replace operation
    597     */
    598    public String replace(final char[] source) {
    599        if (source == null) {
    600            return null;
    601        }
    602        final TextStringBuilder buf = new TextStringBuilder(source.length).append(source);
    603        substitute(buf, 0, source.length);
    604        return buf.toString();
    605    }
    606
    607    /**
    608     * Replaces all the occurrences of variables with their matching values from the resolver using the given source
    609     * array as a template. The array is not altered by this method.
    610     * <p>
    611     * Only the specified portion of the array will be processed. The rest of the array is not processed, and is not
    612     * returned.
    613     *
    614     * @param source
    615     *            the character array to replace in, not altered, null returns null
    616     * @param offset
    617     *            the start offset within the array, must be valid
    618     * @param length
    619     *            the length within the array to be processed, must be valid
    620     * @return the result of the replace operation
    621     */
    622    public String replace(final char[] source, final int offset, final int length) {
    623        if (source == null) {
    624            return null;
    625        }
    626        final TextStringBuilder buf = new TextStringBuilder(length).append(source, offset, length);
    627        substitute(buf, 0, length);
    628        return buf.toString();
    629    }
    630
    631    /**
    632     * Replaces all the occurrences of variables with their matching values from the resolver using the given source as
    633     * a template. The source is not altered by this method.
    634     *
    635     * @param source
    636     *            the buffer to use as a template, not changed, null returns null
    637     * @return the result of the replace operation
    638     */
    639    public String replace(final CharSequence source) {
    640        if (source == null) {
    641            return null;
    642        }
    643        return replace(source, 0, source.length());
    644    }
    645
    646    /**
    647     * Replaces all the occurrences of variables with their matching values from the resolver using the given source as
    648     * a template. The source is not altered by this method.
    649     * <p>
    650     * Only the specified portion of the buffer will be processed. The rest of the buffer is not processed, and is not
    651     * returned.
    652     *
    653     * @param source
    654     *            the buffer to use as a template, not changed, null returns null
    655     * @param offset
    656     *            the start offset within the array, must be valid
    657     * @param length
    658     *            the length within the array to be processed, must be valid
    659     * @return the result of the replace operation
    660     */
    661    public String replace(final CharSequence source, final int offset, final int length) {
    662        if (source == null) {
    663            return null;
    664        }
    665        final TextStringBuilder buf = new TextStringBuilder(length).append(source, offset, length);
    666        substitute(buf, 0, length);
    667        return buf.toString();
    668    }
    669
    670    // -----------------------------------------------------------------------
    671    /**
    672     * Replaces all the occurrences of variables in the given source object with their matching values from the
    673     * resolver. The input source object is converted to a string using <code>toString</code> and is not altered.
    674     *
    675     * @param source
    676     *            the source to replace in, null returns null
    677     * @return the result of the replace operation
    678     */
    679    public String replace(final Object source) {
    680        if (source == null) {
    681            return null;
    682        }
    683        final TextStringBuilder buf = new TextStringBuilder().append(source);
    684        substitute(buf, 0, buf.length());
    685        return buf.toString();
    686    }
    687
    688    // -----------------------------------------------------------------------
    689    /**
    690     * Replaces all the occurrences of variables with their matching values from the resolver using the given source
    691     * builder as a template. The builder is not altered by this method.
    692     *
    693     * @param source
    694     *            the builder to use as a template, not changed, null returns null
    695     * @return the result of the replace operation
    696     */
    697    public String replace(final TextStringBuilder source) {
    698        if (source == null) {
    699            return null;
    700        }
    701        final TextStringBuilder buf = new TextStringBuilder(source.length()).append(source);
    702        substitute(buf, 0, buf.length());
    703        return buf.toString();
    704    }
    705
    706    /**
    707     * Replaces all the occurrences of variables with their matching values from the resolver using the given source
    708     * builder as a template. The builder is not altered by this method.
    709     * <p>
    710     * Only the specified portion of the builder will be processed. The rest of the builder is not processed, and is not
    711     * returned.
    712     *
    713     * @param source
    714     *            the builder to use as a template, not changed, null returns null
    715     * @param offset
    716     *            the start offset within the array, must be valid
    717     * @param length
    718     *            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 TextStringBuilder source, final int offset, final int length) {
    722        if (source == null) {
    723            return null;
    724        }
    725        final TextStringBuilder buf = new TextStringBuilder(length).append(source, offset, length);
    726        substitute(buf, 0, length);
    727        return buf.toString();
    728    }
    729
    730    // -----------------------------------------------------------------------
    731    /**
    732     * Replaces all the occurrences of variables with their matching values from the resolver using the given source
    733     * string as a template.
    734     *
    735     * @param source
    736     *            the string to replace in, null returns null
    737     * @return the result of the replace operation
    738     */
    739    public String replace(final String source) {
    740        if (source == null) {
    741            return null;
    742        }
    743        final TextStringBuilder buf = new TextStringBuilder(source);
    744        if (!substitute(buf, 0, source.length())) {
    745            return source;
    746        }
    747        return buf.toString();
    748    }
    749
    750    /**
    751     * Replaces all the occurrences of variables with their matching values from the resolver using the given source
    752     * string as a template.
    753     * <p>
    754     * Only the specified portion of the string will be processed. The rest of the string is not processed, and is not
    755     * returned.
    756     *
    757     * @param source
    758     *            the string to replace in, null returns null
    759     * @param offset
    760     *            the start offset within the array, must be valid
    761     * @param length
    762     *            the length within the array to be processed, must be valid
    763     * @return the result of the replace operation
    764     */
    765    public String replace(final String source, final int offset, final int length) {
    766        if (source == null) {
    767            return null;
    768        }
    769        final TextStringBuilder buf = new TextStringBuilder(length).append(source, offset, length);
    770        if (!substitute(buf, 0, length)) {
    771            return source.substring(offset, offset + length);
    772        }
    773        return buf.toString();
    774    }
    775
    776    // -----------------------------------------------------------------------
    777    /**
    778     * Replaces all the occurrences of variables with their matching values from the resolver using the given source
    779     * buffer as a template. The buffer is not altered by this method.
    780     *
    781     * @param source
    782     *            the buffer to use as a template, not changed, null returns null
    783     * @return the result of the replace operation
    784     */
    785    public String replace(final StringBuffer source) {
    786        if (source == null) {
    787            return null;
    788        }
    789        final TextStringBuilder buf = new TextStringBuilder(source.length()).append(source);
    790        substitute(buf, 0, buf.length());
    791        return buf.toString();
    792    }
    793
    794    /**
    795     * Replaces all the occurrences of variables with their matching values from the resolver using the given source
    796     * buffer as a template. The buffer is not altered by this method.
    797     * <p>
    798     * Only the specified portion of the buffer will be processed. The rest of the buffer is not processed, and is not
    799     * returned.
    800     *
    801     * @param source
    802     *            the buffer to use as a template, not changed, null returns null
    803     * @param offset
    804     *            the start offset within the array, must be valid
    805     * @param length
    806     *            the length within the array to be processed, must be valid
    807     * @return the result of the replace operation
    808     */
    809    public String replace(final StringBuffer source, final int offset, final int length) {
    810        if (source == null) {
    811            return null;
    812        }
    813        final TextStringBuilder buf = new TextStringBuilder(length).append(source, offset, length);
    814        substitute(buf, 0, length);
    815        return buf.toString();
    816    }
    817
    818    // -----------------------------------------------------------------------
    819    /**
    820     * Replaces all the occurrences of variables within the given source builder with their matching values from the
    821     * resolver.
    822     *
    823     * @param source
    824     *            the builder to replace in, updated, null returns zero
    825     * @return true if altered
    826     */
    827    public boolean replaceIn(final TextStringBuilder source) {
    828        if (source == null) {
    829            return false;
    830        }
    831        return substitute(source, 0, source.length());
    832    }
    833
    834    /**
    835     * Replaces all the occurrences of variables within the given source builder with their matching values from the
    836     * resolver.
    837     * <p>
    838     * Only the specified portion of the builder will be processed. The rest of the builder is not processed, but it is
    839     * not deleted.
    840     *
    841     * @param source
    842     *            the builder to replace in, null returns zero
    843     * @param offset
    844     *            the start offset within the array, must be valid
    845     * @param length
    846     *            the length within the builder to be processed, must be valid
    847     * @return true if altered
    848     */
    849    public boolean replaceIn(final TextStringBuilder source, final int offset, final int length) {
    850        if (source == null) {
    851            return false;
    852        }
    853        return substitute(source, offset, length);
    854    }
    855
    856    // -----------------------------------------------------------------------
    857    /**
    858     * Replaces all the occurrences of variables within the given source buffer with their matching values from the
    859     * resolver. The buffer is updated with the result.
    860     *
    861     * @param source
    862     *            the buffer to replace in, updated, null returns zero
    863     * @return true if altered
    864     */
    865    public boolean replaceIn(final StringBuffer source) {
    866        if (source == null) {
    867            return false;
    868        }
    869        return replaceIn(source, 0, source.length());
    870    }
    871
    872    /**
    873     * Replaces all the occurrences of variables within the given source buffer with their matching values from the
    874     * resolver. The buffer is updated with the result.
    875     * <p>
    876     * Only the specified portion of the buffer will be processed. The rest of the buffer is not processed, but it is
    877     * not deleted.
    878     *
    879     * @param source
    880     *            the buffer to replace in, updated, null returns zero
    881     * @param offset
    882     *            the start offset within the array, must be valid
    883     * @param length
    884     *            the length within the buffer to be processed, must be valid
    885     * @return true if altered
    886     */
    887    public boolean replaceIn(final StringBuffer source, final int offset, final int length) {
    888        if (source == null) {
    889            return false;
    890        }
    891        final TextStringBuilder buf = new TextStringBuilder(length).append(source, offset, length);
    892        if (!substitute(buf, 0, length)) {
    893            return false;
    894        }
    895        source.replace(offset, offset + length, buf.toString());
    896        return true;
    897    }
    898
    899    // -----------------------------------------------------------------------
    900    /**
    901     * Replaces all the occurrences of variables within the given source buffer with their matching values from the
    902     * resolver. The buffer is updated with the result.
    903     *
    904     * @param source
    905     *            the buffer to replace in, updated, null returns zero
    906     * @return true if altered
    907     */
    908    public boolean replaceIn(final StringBuilder source) {
    909        if (source == null) {
    910            return false;
    911        }
    912        return replaceIn(source, 0, source.length());
    913    }
    914
    915    /**
    916     * Replaces all the occurrences of variables within the given source builder with their matching values from the
    917     * resolver. The builder is updated with the result.
    918     * <p>
    919     * Only the specified portion of the buffer will be processed. The rest of the buffer is not processed, but it is
    920     * not deleted.
    921     *
    922     * @param source
    923     *            the buffer to replace in, updated, null returns zero
    924     * @param offset
    925     *            the start offset within the array, must be valid
    926     * @param length
    927     *            the length within the buffer to be processed, must be valid
    928     * @return true if altered
    929     */
    930    public boolean replaceIn(final StringBuilder source, final int offset, final int length) {
    931        if (source == null) {
    932            return false;
    933        }
    934        final TextStringBuilder buf = new TextStringBuilder(length).append(source, offset, length);
    935        if (!substitute(buf, 0, length)) {
    936            return false;
    937        }
    938        source.replace(offset, offset + length, buf.toString());
    939        return true;
    940    }
    941
    942    /**
    943     * Internal method that resolves the value of a variable.
    944     * <p>
    945     * Most users of this class do not need to call this method. This method is called automatically by the substitution
    946     * process.
    947     * <p>
    948     * Writers of subclasses can override this method if they need to alter how each substitution occurs. The method is
    949     * passed the variable's name and must return the corresponding value. This implementation uses the
    950     * {@link #getStringLookup()} with the variable's name as the key.
    951     *
    952     * @param variableName
    953     *            the name of the variable, not null
    954     * @param buf
    955     *            the buffer where the substitution is occurring, not null
    956     * @param startPos
    957     *            the start position of the variable including the prefix, valid
    958     * @param endPos
    959     *            the end position of the variable including the suffix, valid
    960     * @return the variable's value or <b>null</b> if the variable is unknown
    961     */
    962    protected String resolveVariable(final String variableName, final TextStringBuilder buf, final int startPos,
    963            final int endPos) {
    964        final StringLookup resolver = getStringLookup();
    965        if (resolver == null) {
    966            return null;
    967        }
    968        return resolver.lookup(variableName);
    969    }
    970
    971    /**
    972     * Sets a flag whether substitution is done in variable values (recursive).
    973     *
    974     * @param disableSubstitutionInValues
    975     *            true if substitution in variable value are disabled
    976     * @return this, to enable chaining
    977     */
    978    public StringSubstitutor setDisableSubstitutionInValues(final boolean disableSubstitutionInValues) {
    979        this.disableSubstitutionInValues = disableSubstitutionInValues;
    980        return this;
    981    }
    982
    983    /**
    984     * Sets a flag whether substitution is done in variable names. If set to <b>true</b>, the names of variables can
    985     * contain other variables which are processed first before the original variable is evaluated, e.g.
    986     * <code>${jre-${java.version}}</code>. The default value is <b>false</b>.
    987     *
    988     * @param enableSubstitutionInVariables
    989     *            the new value of the flag
    990     * @return this, to enable chaining
    991     */
    992    public StringSubstitutor setEnableSubstitutionInVariables(final boolean enableSubstitutionInVariables) {
    993        this.enableSubstitutionInVariables = enableSubstitutionInVariables;
    994        return this;
    995    }
    996
    997    /**
    998     * Sets the escape character. If this character is placed before a variable reference in the source text, this
    999     * variable will be ignored.
    1000     *
    1001     * @param escapeCharacter
    1002     *            the escape character (0 for disabling escaping)
    1003     * @return this, to enable chaining
    1004     */
    1005    public StringSubstitutor setEscapeChar(final char escapeCharacter) {
    1006        this.escapeChar = escapeCharacter;
    1007        return this;
    1008    }
    1009
    1010    /**
    1011     * Sets a flag controlling whether escapes are preserved during substitution. If set to <b>true</b>, the escape
    1012     * character is retained during substitution (e.g. <code>$${this-is-escaped}</code> remains
    1013     * <code>$${this-is-escaped}</code>). If set to <b>false</b>, the escape character is removed during substitution
    1014     * (e.g. <code>$${this-is-escaped}</code> becomes <code>${this-is-escaped}</code>). The default value is
    1015     * <b>false</b>
    1016     *
    1017     * @param preserveEscapes
    1018     *            true if escapes are to be preserved
    1019     * @return this, to enable chaining
    1020     */
    1021    public StringSubstitutor setPreserveEscapes(final boolean preserveEscapes) {
    1022        this.preserveEscapes = preserveEscapes;
    1023        return this;
    1024    }
    1025
    1026    /**
    1027     * Sets the variable default value delimiter to use.
    1028     * <p>
    1029     * The variable default value delimiter is the character or characters that delimite the variable name and the
    1030     * variable default value. This method allows a single character variable default value delimiter to be easily set.
    1031     *
    1032     * @param valueDelimiter
    1033     *            the variable default value delimiter character to use
    1034     * @return this, to enable chaining
    1035     */
    1036    public StringSubstitutor setValueDelimiter(final char valueDelimiter) {
    1037        return setValueDelimiterMatcher(StringMatcherFactory.INSTANCE.charMatcher(valueDelimiter));
    1038    }
    1039
    1040    /**
    1041     * Sets the variable default value delimiter to use.
    1042     * <p>
    1043     * The variable default value delimiter is the character or characters that delimite the variable name and the
    1044     * variable default value. This method allows a string variable default value delimiter to be easily set.
    1045     * <p>
    1046     * If the <code>valueDelimiter</code> is null or empty string, then the variable default value resolution becomes
    1047     * disabled.
    1048     *
    1049     * @param valueDelimiter
    1050     *            the variable default value delimiter string to use, may be null or empty
    1051     * @return this, to enable chaining
    1052     */
    1053    public StringSubstitutor setValueDelimiter(final String valueDelimiter) {
    1054        if (valueDelimiter == null || valueDelimiter.length() == 0) {
    1055            setValueDelimiterMatcher(null);
    1056            return this;
    1057        }
    1058        return setValueDelimiterMatcher(StringMatcherFactory.INSTANCE.stringMatcher(valueDelimiter));
    1059    }
    1060
    1061    /**
    1062     * Sets the variable default value delimiter matcher to use.
    1063     * <p>
    1064     * The variable default value delimiter is the character or characters that delimite the variable name and the
    1065     * variable default value. This delimiter is expressed in terms of a matcher allowing advanced variable default
    1066     * value delimiter matches.
    1067     * <p>
    1068     * If the <code>valueDelimiterMatcher</code> is null, then the variable default value resolution becomes disabled.
    1069     *
    1070     * @param valueDelimiterMatcher
    1071     *            variable default value delimiter matcher to use, may be null
    1072     * @return this, to enable chaining
    1073     */
    1074    public StringSubstitutor setValueDelimiterMatcher(final StringMatcher valueDelimiterMatcher) {
    1075        this.valueDelimiterMatcher = valueDelimiterMatcher;
    1076        return this;
    1077    }
    1078
    1079    /**
    1080     * Sets the variable prefix to use.
    1081     * <p>
    1082     * The variable prefix is the character or characters that identify the start of a variable. This method allows a
    1083     * single character prefix to be easily set.
    1084     *
    1085     * @param prefix
    1086     *            the prefix character to use
    1087     * @return this, to enable chaining
    1088     */
    1089    public StringSubstitutor setVariablePrefix(final char prefix) {
    1090        return setVariablePrefixMatcher(StringMatcherFactory.INSTANCE.charMatcher(prefix));
    1091    }
    1092
    1093    /**
    1094     * Sets the variable prefix to use.
    1095     * <p>
    1096     * The variable prefix is the character or characters that identify the start of a variable. This method allows a
    1097     * string prefix to be easily set.
    1098     *
    1099     * @param prefix
    1100     *            the prefix for variables, not null
    1101     * @return this, to enable chaining
    1102     * @throws IllegalArgumentException
    1103     *             if the prefix is null
    1104     */
    1105    public StringSubstitutor setVariablePrefix(final String prefix) {
    1106        Validate.isTrue(prefix != null, "Variable prefix must not be null!");
    1107        return setVariablePrefixMatcher(StringMatcherFactory.INSTANCE.stringMatcher(prefix));
    1108    }
    1109
    1110    /**
    1111     * Sets the variable prefix matcher currently in use.
    1112     * <p>
    1113     * The variable prefix is the character or characters that identify the start of a variable. This prefix is
    1114     * expressed in terms of a matcher allowing advanced prefix matches.
    1115     *
    1116     * @param prefixMatcher
    1117     *            the prefix matcher to use, null ignored
    1118     * @return this, to enable chaining
    1119     * @throws IllegalArgumentException
    1120     *             if the prefix matcher is null
    1121     */
    1122    public StringSubstitutor setVariablePrefixMatcher(final StringMatcher prefixMatcher) {
    1123        Validate.isTrue(prefixMatcher != null, "Variable prefix matcher must not be null!");
    1124        this.prefixMatcher = prefixMatcher;
    1125        return this;
    1126    }
    1127
    1128    /**
    1129     * Sets the VariableResolver that is used to lookup variables.
    1130     *
    1131     * @param variableResolver
    1132     *            the VariableResolver
    1133     * @return this, to enable chaining
    1134     */
    1135    public StringSubstitutor setVariableResolver(final StringLookup variableResolver) {
    1136        this.variableResolver = variableResolver;
    1137        return this;
    1138    }
    1139
    1140    /**
    1141     * Sets the variable suffix to use.
    1142     * <p>
    1143     * The variable suffix is the character or characters that identify the end of a variable. This method allows a
    1144     * single character suffix to be easily set.
    1145     *
    1146     * @param suffix
    1147     *            the suffix character to use
    1148     * @return this, to enable chaining
    1149     */
    1150    public StringSubstitutor setVariableSuffix(final char suffix) {
    1151        return setVariableSuffixMatcher(StringMatcherFactory.INSTANCE.charMatcher(suffix));
    1152    }
    1153
    1154    /**
    1155     * Sets the variable suffix to use.
    1156     * <p>
    1157     * The variable suffix is the character or characters that identify the end of a variable. This method allows a
    1158     * string suffix to be easily set.
    1159     *
    1160     * @param suffix
    1161     *            the suffix for variables, not null
    1162     * @return this, to enable chaining
    1163     * @throws IllegalArgumentException
    1164     *             if the suffix is null
    1165     */
    1166    public StringSubstitutor setVariableSuffix(final String suffix) {
    1167        Validate.isTrue(suffix != null, "Variable suffix must not be null!");
    1168        return setVariableSuffixMatcher(StringMatcherFactory.INSTANCE.stringMatcher(suffix));
    1169    }
    1170
    1171    /**
    1172     * Sets the variable suffix matcher currently in use.
    1173     * <p>
    1174     * The variable suffix is the character or characters that identify the end of a variable. This suffix is expressed
    1175     * in terms of a matcher allowing advanced suffix matches.
    1176     *
    1177     * @param suffixMatcher
    1178     *            the suffix matcher to use, null ignored
    1179     * @return this, to enable chaining
    1180     * @throws IllegalArgumentException
    1181     *             if the suffix matcher is null
    1182     */
    1183    public StringSubstitutor setVariableSuffixMatcher(final StringMatcher suffixMatcher) {
    1184        Validate.isTrue(suffixMatcher != null, "Variable suffix matcher must not be null!");
    1185        this.suffixMatcher = suffixMatcher;
    1186        return this;
    1187    }
    1188
    1189    // -----------------------------------------------------------------------
    1190    /**
    1191     * Internal method that substitutes the variables.
    1192     * <p>
    1193     * Most users of this class do not need to call this method. This method will be called automatically by another
    1194     * (public) method.
    1195     * <p>
    1196     * Writers of subclasses can override this method if they need access to the substitution process at the start or
    1197     * end.
    1198     *
    1199     * @param buf
    1200     *            the string builder to substitute into, not null
    1201     * @param offset
    1202     *            the start offset within the builder, must be valid
    1203     * @param length
    1204     *            the length within the builder to be processed, must be valid
    1205     * @return true if altered
    1206     */
    1207    protected boolean substitute(final TextStringBuilder buf, final int offset, final int length) {
    1208        return substitute(buf, offset, length, null) > 0;
    1209    }
    1210
    1211    /**
    1212     * Recursive handler for multiple levels of interpolation. This is the main interpolation method, which resolves the
    1213     * values of all variable references contained in the passed in text.
    1214     *
    1215     * @param buf
    1216     *            the string builder to substitute into, not null
    1217     * @param offset
    1218     *            the start offset within the builder, must be valid
    1219     * @param length
    1220     *            the length within the builder to be processed, must be valid
    1221     * @param priorVariables
    1222     *            the stack keeping track of the replaced variables, may be null
    1223     * @return the length change that occurs, unless priorVariables is null when the int represents a boolean flag as to
    1224     *         whether any change occurred.
    1225     */
    1226    private int substitute(final TextStringBuilder buf, final int offset, final int length,
    1227            List<String> priorVariables) {
    1228        final StringMatcher pfxMatcher = getVariablePrefixMatcher();
    1229        final StringMatcher suffMatcher = getVariableSuffixMatcher();
    1230        final char escape = getEscapeChar();
    1231        final StringMatcher valueDelimMatcher = getValueDelimiterMatcher();
    1232        final boolean substitutionInVariablesEnabled = isEnableSubstitutionInVariables();
    1233        final boolean substitutionInValuesDisabled = isDisableSubstitutionInValues();
    1234
    1235        final boolean top = priorVariables == null;
    1236        boolean altered = false;
    1237        int lengthChange = 0;
    1238        char[] chars = buf.buffer;
    1239        int bufEnd = offset + length;
    1240        int pos = offset;
    1241        while (pos < bufEnd) {
    1242            final int startMatchLen = pfxMatcher.isMatch(chars, pos, offset, bufEnd);
    1243            if (startMatchLen == 0) {
    1244                pos++;
    1245            } else {
    1246                // found variable start marker
    1247                if (pos > offset && chars[pos - 1] == escape) {
    1248                    // escaped
    1249                    if (preserveEscapes) {
    1250                        pos++;
    1251                        continue;
    1252                    }
    1253                    buf.deleteCharAt(pos - 1);
    1254                    chars = buf.buffer; // in case buffer was altered
    1255                    lengthChange--;
    1256                    altered = true;
    1257                    bufEnd--;
    1258                } else {
    1259                    // find suffix
    1260                    final int startPos = pos;
    1261                    pos += startMatchLen;
    1262                    int endMatchLen = 0;
    1263                    int nestedVarCount = 0;
    1264                    while (pos < bufEnd) {
    1265                        if (substitutionInVariablesEnabled && pfxMatcher.isMatch(chars, pos, offset, bufEnd) != 0) {
    1266                            // found a nested variable start
    1267                            endMatchLen = pfxMatcher.isMatch(chars, pos, offset, bufEnd);
    1268                            nestedVarCount++;
    1269                            pos += endMatchLen;
    1270                            continue;
    1271                        }
    1272
    1273                        endMatchLen = suffMatcher.isMatch(chars, pos, offset, bufEnd);
    1274                        if (endMatchLen == 0) {
    1275                            pos++;
    1276                        } else {
    1277                            // found variable end marker
    1278                            if (nestedVarCount == 0) {
    1279                                String varNameExpr = new String(chars, startPos + startMatchLen,
    1280                                        pos - startPos - startMatchLen);
    1281                                if (substitutionInVariablesEnabled) {
    1282                                    final TextStringBuilder bufName = new TextStringBuilder(varNameExpr);
    1283                                    substitute(bufName, 0, bufName.length());
    1284                                    varNameExpr = bufName.toString();
    1285                                }
    1286                                pos += endMatchLen;
    1287                                final int endPos = pos;
    1288
    1289                                String varName = varNameExpr;
    1290                                String varDefaultValue = null;
    1291
    1292                                if (valueDelimMatcher != null) {
    1293                                    final char[] varNameExprChars = varNameExpr.toCharArray();
    1294                                    int valueDelimiterMatchLen = 0;
    1295                                    for (int i = 0; i < varNameExprChars.length; i++) {
    1296                                        // if there's any nested variable when nested variable substitution disabled,
    1297                                        // then stop resolving name and default value.
    1298                                        if (!substitutionInVariablesEnabled && pfxMatcher.isMatch(varNameExprChars, i,
    1299                                                i, varNameExprChars.length) != 0) {
    1300                                            break;
    1301                                        }
    1302                                        if (valueDelimMatcher.isMatch(varNameExprChars, i, 0,
    1303                                                varNameExprChars.length) != 0) {
    1304                                            valueDelimiterMatchLen = valueDelimMatcher.isMatch(varNameExprChars, i, 0,
    1305                                                    varNameExprChars.length);
    1306                                            varName = varNameExpr.substring(0, i);
    1307                                            varDefaultValue = varNameExpr.substring(i + valueDelimiterMatchLen);
    1308                                            break;
    1309                                        }
    1310                                    }
    1311                                }
    1312
    1313                                // on the first call initialize priorVariables
    1314                                if (priorVariables == null) {
    1315                                    priorVariables = new ArrayList<>();
    1316                                    priorVariables.add(new String(chars, offset, length));
    1317                                }
    1318
    1319                                // handle cyclic substitution
    1320                                checkCyclicSubstitution(varName, priorVariables);
    1321                                priorVariables.add(varName);
    1322
    1323                                // resolve the variable
    1324                                String varValue = resolveVariable(varName, buf, startPos, endPos);
    1325                                if (varValue == null) {
    1326                                    varValue = varDefaultValue;
    1327                                }
    1328                                if (varValue != null) {
    1329                                    final int varLen = varValue.length();
    1330                                    buf.replace(startPos, endPos, varValue);
    1331                                    altered = true;
    1332                                    int change = 0;
    1333                                    if (!substitutionInValuesDisabled) { // recursive replace
    1334                                        change = substitute(buf, startPos, varLen, priorVariables);
    1335                                    }
    1336                                    change = change + varLen - (endPos - startPos);
    1337                                    pos += change;
    1338                                    bufEnd += change;
    1339                                    lengthChange += change;
    1340                                    chars = buf.buffer; // in case buffer was
    1341                                                        // altered
    1342                                }
    1343
    1344                                // remove variable from the cyclic stack
    1345                                priorVariables.remove(priorVariables.size() - 1);
    1346                                break;
    1347                            }
    1348                            nestedVarCount--;
    1349                            pos += endMatchLen;
    1350                        }
    1351                    }
    1352                }
    1353            }
    1354        }
    1355        if (top) {
    1356            return altered ? 1 : 0;
    1357        }
    1358        return lengthChange;
    1359    }
    1360}