org.apache.commons.lang.text.StrSubstitutor Maven / Gradle / Ivy
Show all versions of commons-lang Show documentation
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.lang.text;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
/**
* Substitutes variables within a string by values.
*
* This class takes a piece of text and substitutes all the variables within it.
* The default definition of a variable is ${variableName}.
* The prefix and suffix can be changed via constructors and set methods.
*
* Variable values are typically resolved from a map, but could also be resolved
* from system properties, or by supplying a custom variable resolver.
*
* The simplest example is to use this class to replace Java System properties. For example:
*
* StrSubstitutor.replaceSystemProperties(
* "You are running with java.version = ${java.version} and os.name = ${os.name}.");
*
*
* Typical usage of this class follows the following pattern: First an instance is created
* and initialized with the map that contains the values for the available variables.
* If a prefix and/or suffix for variables should be used other than the default ones,
* the appropriate settings can be performed. After that the replace()
* method can be called passing in the source text for interpolation. In the returned
* text all variable references (as long as their values are known) will be resolved.
* The following example demonstrates this:
*
* Map valuesMap = HashMap();
* valuesMap.put("animal", "quick brown fox");
* valuesMap.put("target", "lazy dog");
* String templateString = "The ${animal} jumped over the ${target}.";
* StrSubstitutor sub = new StrSubstitutor(valuesMap);
* String resolvedString = sub.replace(templateString);
*
* yielding:
*
* The quick brown fox jumped over the lazy dog.
*
*
* In addition to this usage pattern there are some static convenience methods that
* cover the most common use cases. These methods can be used without the need of
* manually creating an instance. However if multiple replace operations are to be
* performed, creating and reusing an instance of this class will be more efficient.
*
* Variable replacement works in a recursive way. Thus, if a variable value contains
* a variable then that variable will also be replaced. Cyclic replacements are
* detected and will cause an exception to be thrown.
*
* Sometimes the interpolation's result must contain a variable prefix. As an example
* take the following source text:
*
* The variable ${${name}} must be used.
*
* Here only the variable's name refered to in the text should be replaced resulting
* in the text (assuming that the value of the name variable is x):
*
* The variable ${x} must be used.
*
* To achieve this effect there are two possibilities: Either set a different prefix
* and suffix for variables which do not conflict with the result text you want to
* produce. The other possibility is to use the escape character, by default '$'.
* If this character is placed before a variable reference, this reference is ignored
* and won't be replaced. For example:
*
* The variable $${${name}} must be used.
*
*
* @author Oliver Heger
* @author Stephen Colebourne
* @version $Id: StrSubstitutor.java 437554 2006-08-28 06:21:41Z bayard $
* @since 2.2
*/
public class StrSubstitutor {
/**
* Constant for the default escape character.
*/
public static final char DEFAULT_ESCAPE = '$';
/**
* Constant for the default variable prefix.
*/
public static final StrMatcher DEFAULT_PREFIX = StrMatcher.stringMatcher("${");
/**
* Constant for the default variable suffix.
*/
public static final StrMatcher DEFAULT_SUFFIX = StrMatcher.stringMatcher("}");
/**
* Stores the escape character.
*/
private char escapeChar;
/**
* Stores the variable prefix.
*/
private StrMatcher prefixMatcher;
/**
* Stores the variable suffix.
*/
private StrMatcher suffixMatcher;
/**
* Variable resolution is delegated to an implementor of VariableResolver.
*/
private StrLookup variableResolver;
//-----------------------------------------------------------------------
/**
* Replaces all the occurrences of variables in the given source object with
* their matching values from the map.
*
* @param source the source text containing the variables to substitute, null returns null
* @param valueMap the map with the values, may be null
* @return the result of the replace operation
*/
public static String replace(Object source, Map valueMap) {
return new StrSubstitutor(valueMap).replace(source);
}
/**
* Replaces all the occurrences of variables in the given source object with
* their matching values from the map. This method allows to specifiy a
* custom variable prefix and suffix
*
* @param source the source text containing the variables to substitute, null returns null
* @param valueMap the map with the values, may be null
* @param prefix the prefix of variables, not null
* @param suffix the suffix of variables, not null
* @return the result of the replace operation
* @throws IllegalArgumentException if the prefix or suffix is null
*/
public static String replace(Object source, Map valueMap, String prefix, String suffix) {
return new StrSubstitutor(valueMap, prefix, suffix).replace(source);
}
/**
* Replaces all the occurrences of variables in the given source object with
* their matching values from the system properties.
*
* @param source the source text containing the variables to substitute, null returns null
* @return the result of the replace operation
*/
public static String replaceSystemProperties(Object source) {
return new StrSubstitutor(StrLookup.systemPropertiesLookup()).replace(source);
}
//-----------------------------------------------------------------------
/**
* Creates a new instance with defaults for variable prefix and suffix
* and the escaping character.
*/
public StrSubstitutor() {
this((StrLookup) null, DEFAULT_PREFIX, DEFAULT_SUFFIX, DEFAULT_ESCAPE);
}
/**
* Creates a new instance and initializes it. Uses defaults for variable
* prefix and suffix and the escaping character.
*
* @param valueMap the map with the variables' values, may be null
*/
public StrSubstitutor(Map valueMap) {
this(StrLookup.mapLookup(valueMap), DEFAULT_PREFIX, DEFAULT_SUFFIX, DEFAULT_ESCAPE);
}
/**
* Creates a new instance and initializes it. Uses a default escaping character.
*
* @param valueMap the map with the variables' values, may be null
* @param prefix the prefix for variables, not null
* @param suffix the suffix for variables, not null
* @throws IllegalArgumentException if the prefix or suffix is null
*/
public StrSubstitutor(Map valueMap, String prefix, String suffix) {
this(StrLookup.mapLookup(valueMap), prefix, suffix, DEFAULT_ESCAPE);
}
/**
* Creates a new instance and initializes it.
*
* @param valueMap the map with the variables' values, may be null
* @param prefix the prefix for variables, not null
* @param suffix the suffix for variables, not null
* @param escape the escape character
* @throws IllegalArgumentException if the prefix or suffix is null
*/
public StrSubstitutor(Map valueMap, String prefix, String suffix, char escape) {
this(StrLookup.mapLookup(valueMap), prefix, suffix, escape);
}
/**
* Creates a new instance and initializes it.
*
* @param variableResolver the variable resolver, may be null
*/
public StrSubstitutor(StrLookup variableResolver) {
this(variableResolver, DEFAULT_PREFIX, DEFAULT_SUFFIX, DEFAULT_ESCAPE);
}
/**
* Creates a new instance and initializes it.
*
* @param variableResolver the variable resolver, may be null
* @param prefix the prefix for variables, not null
* @param suffix the suffix for variables, not null
* @param escape the escape character
* @throws IllegalArgumentException if the prefix or suffix is null
*/
public StrSubstitutor(StrLookup variableResolver, String prefix, String suffix, char escape) {
this.setVariableResolver(variableResolver);
this.setVariablePrefix(prefix);
this.setVariableSuffix(suffix);
this.setEscapeChar(escape);
}
/**
* Creates a new instance and initializes it.
*
* @param variableResolver the variable resolver, may be null
* @param prefixMatcher the prefix for variables, not null
* @param suffixMatcher the suffix for variables, not null
* @param escape the escape character
* @throws IllegalArgumentException if the prefix or suffix is null
*/
public StrSubstitutor(
StrLookup variableResolver, StrMatcher prefixMatcher, StrMatcher suffixMatcher, char escape) {
this.setVariableResolver(variableResolver);
this.setVariablePrefixMatcher(prefixMatcher);
this.setVariableSuffixMatcher(suffixMatcher);
this.setEscapeChar(escape);
}
//-----------------------------------------------------------------------
/**
* Replaces all the occurrences of variables with their matching values
* from the resolver using the given source string as a template.
*
* @param source the string to replace in, null returns null
* @return the result of the replace operation
*/
public String replace(String source) {
if (source == null) {
return null;
}
StrBuilder buf = new StrBuilder(source);
if (substitute(buf, 0, source.length()) == false) {
return source;
}
return buf.toString();
}
/**
* Replaces all the occurrences of variables with their matching values
* from the resolver using the given source string as a template.
*
* Only the specified portion of the string will be processed.
* The rest of the string is not processed, and is not returned.
*
* @param source the string to replace in, null returns null
* @param offset the start offset within the array, must be valid
* @param length the length within the array to be processed, must be valid
* @return the result of the replace operation
*/
public String replace(String source, int offset, int length) {
if (source == null) {
return null;
}
StrBuilder buf = new StrBuilder(length).append(source, offset, length);
if (substitute(buf, 0, length) == false) {
return source.substring(offset, offset + length);
}
return buf.toString();
}
//-----------------------------------------------------------------------
/**
* Replaces all the occurrences of variables with their matching values
* from the resolver using the given source array as a template.
* The array is not altered by this method.
*
* @param source the character array to replace in, not altered, null returns null
* @return the result of the replace operation
*/
public String replace(char[] source) {
if (source == null) {
return null;
}
StrBuilder buf = new StrBuilder(source.length).append(source);
substitute(buf, 0, source.length);
return buf.toString();
}
/**
* Replaces all the occurrences of variables with their matching values
* from the resolver using the given source array as a template.
* The array is not altered by this method.
*
* Only the specified portion of the array will be processed.
* The rest of the array is not processed, and is not returned.
*
* @param source the character array to replace in, not altered, null returns null
* @param offset the start offset within the array, must be valid
* @param length the length within the array to be processed, must be valid
* @return the result of the replace operation
*/
public String replace(char[] source, int offset, int length) {
if (source == null) {
return null;
}
StrBuilder buf = new StrBuilder(length).append(source, offset, length);
substitute(buf, 0, length);
return buf.toString();
}
//-----------------------------------------------------------------------
/**
* Replaces all the occurrences of variables with their matching values
* from the resolver using the given source buffer as a template.
* The buffer is not altered by this method.
*
* @param source the buffer to use as a template, not changed, null returns null
* @return the result of the replace operation
*/
public String replace(StringBuffer source) {
if (source == null) {
return null;
}
StrBuilder buf = new StrBuilder(source.length()).append(source);
substitute(buf, 0, buf.length());
return buf.toString();
}
/**
* Replaces all the occurrences of variables with their matching values
* from the resolver using the given source buffer as a template.
* The buffer is not altered by this method.
*
* Only the specified portion of the buffer will be processed.
* The rest of the buffer is not processed, and is not returned.
*
* @param source the buffer to use as a template, not changed, null returns null
* @param offset the start offset within the array, must be valid
* @param length the length within the array to be processed, must be valid
* @return the result of the replace operation
*/
public String replace(StringBuffer source, int offset, int length) {
if (source == null) {
return null;
}
StrBuilder buf = new StrBuilder(length).append(source, offset, length);
substitute(buf, 0, length);
return buf.toString();
}
//-----------------------------------------------------------------------
/**
* Replaces all the occurrences of variables with their matching values
* from the resolver using the given source builder as a template.
* The builder is not altered by this method.
*
* @param source the builder to use as a template, not changed, null returns null
* @return the result of the replace operation
*/
public String replace(StrBuilder source) {
if (source == null) {
return null;
}
StrBuilder buf = new StrBuilder(source.length()).append(source);
substitute(buf, 0, buf.length());
return buf.toString();
}
/**
* Replaces all the occurrences of variables with their matching values
* from the resolver using the given source builder as a template.
* The builder is not altered by this method.
*
* Only the specified portion of the builder will be processed.
* The rest of the builder is not processed, and is not returned.
*
* @param source the builder to use as a template, not changed, null returns null
* @param offset the start offset within the array, must be valid
* @param length the length within the array to be processed, must be valid
* @return the result of the replace operation
*/
public String replace(StrBuilder source, int offset, int length) {
if (source == null) {
return null;
}
StrBuilder buf = new StrBuilder(length).append(source, offset, length);
substitute(buf, 0, length);
return buf.toString();
}
//-----------------------------------------------------------------------
/**
* Replaces all the occurrences of variables in the given source object with
* their matching values from the resolver. The input source object is
* converted to a string using toString and is not altered.
*
* @param source the source to replace in, null returns null
* @return the result of the replace operation
*/
public String replace(Object source) {
if (source == null) {
return null;
}
StrBuilder buf = new StrBuilder().append(source);
substitute(buf, 0, buf.length());
return buf.toString();
}
//-----------------------------------------------------------------------
/**
* Replaces all the occurrences of variables within the given source buffer
* with their matching values from the resolver.
* The buffer is updated with the result.
*
* @param source the buffer to replace in, updated, null returns zero
* @return true if altered
*/
public boolean replaceIn(StringBuffer source) {
if (source == null) {
return false;
}
return replaceIn(source, 0, source.length());
}
/**
* Replaces all the occurrences of variables within the given source buffer
* with their matching values from the resolver.
* The buffer is updated with the result.
*
* Only the specified portion of the buffer will be processed.
* The rest of the buffer is not processed, but it is not deleted.
*
* @param source the buffer to replace in, updated, null returns zero
* @param offset the start offset within the array, must be valid
* @param length the length within the buffer to be processed, must be valid
* @return true if altered
*/
public boolean replaceIn(StringBuffer source, int offset, int length) {
if (source == null) {
return false;
}
StrBuilder buf = new StrBuilder(length).append(source, offset, length);
if (substitute(buf, 0, length) == false) {
return false;
}
source.replace(offset, offset + length, buf.toString());
return true;
}
//-----------------------------------------------------------------------
/**
* Replaces all the occurrences of variables within the given source
* builder with their matching values from the resolver.
*
* @param source the builder to replace in, updated, null returns zero
* @return true if altered
*/
public boolean replaceIn(StrBuilder source) {
if (source == null) {
return false;
}
return substitute(source, 0, source.length());
}
/**
* Replaces all the occurrences of variables within the given source
* builder with their matching values from the resolver.
*
* Only the specified portion of the builder will be processed.
* The rest of the builder is not processed, but it is not deleted.
*
* @param source the builder to replace in, null returns zero
* @param offset the start offset within the array, must be valid
* @param length the length within the builder to be processed, must be valid
* @return true if altered
*/
public boolean replaceIn(StrBuilder source, int offset, int length) {
if (source == null) {
return false;
}
return substitute(source, offset, length);
}
//-----------------------------------------------------------------------
/**
* Internal method that substitutes the variables.
*
* Most users of this class do not need to call this method. This method will
* be called automatically by another (public) method.
*
* Writers of subclasses can override this method if they need access to
* the substitution process at the start or end.
*
* @param buf the string builder to substitute into, not null
* @param offset the start offset within the builder, must be valid
* @param length the length within the builder to be processed, must be valid
* @return true if altered
*/
protected boolean substitute(StrBuilder buf, int offset, int length) {
return substitute(buf, offset, length, null) > 0;
}
/**
* Recursive handler for multiple levels of interpolation. This is the main
* interpolation method, which resolves the values of all variable references
* contained in the passed in text.
*
* @param buf the string builder to substitute into, not null
* @param offset the start offset within the builder, must be valid
* @param length the length within the builder to be processed, must be valid
* @param priorVariables the stack keeping track of the replaced variables, may be null
* @return the length change that occurs, unless priorVariables is null when the int
* represents a boolean flag as to whether any change occurred.
*/
private int substitute(StrBuilder buf, int offset, int length, List priorVariables) {
StrMatcher prefixMatcher = getVariablePrefixMatcher();
StrMatcher suffixMatcher = getVariableSuffixMatcher();
char escape = getEscapeChar();
boolean top = (priorVariables == null);
boolean altered = false;
int lengthChange = 0;
char[] chars = buf.buffer;
int bufEnd = offset + length;
int pos = offset;
while (pos < bufEnd) {
int startMatchLen = prefixMatcher.isMatch(chars, pos, offset, bufEnd);
if (startMatchLen == 0) {
pos++;
} else {
// found variable start marker
if (pos > offset && chars[pos - 1] == escape) {
// escaped
buf.deleteCharAt(pos - 1);
chars = buf.buffer; // in case buffer was altered
lengthChange--;
altered = true;
bufEnd--;
} else {
// find suffix
int startPos = pos;
pos += startMatchLen;
int endMatchLen = 0;
while (pos < bufEnd) {
endMatchLen = suffixMatcher.isMatch(chars, pos, offset, bufEnd);
if (endMatchLen == 0) {
pos++;
} else {
// found variable end marker
String varName = new String(chars, startPos + startMatchLen,
pos - startPos - startMatchLen);
pos += endMatchLen;
int endPos = pos;
// on the first call initialize priorVariables
if (priorVariables == null) {
priorVariables = new ArrayList();
priorVariables.add(new String(chars, offset, length));
}
// handle cyclic substitution
checkCyclicSubstitution(varName, priorVariables);
priorVariables.add(varName);
// resolve the variable
String varValue = resolveVariable(varName, buf, startPos, endPos);
if (varValue != null) {
// recursive replace
int varLen = varValue.length();
buf.replace(startPos, endPos, varValue);
altered = true;
int change = substitute(buf, startPos, varLen, priorVariables);
change = change + (varLen - (endPos - startPos));
pos += change;
bufEnd += change;
lengthChange += change;
chars = buf.buffer; // in case buffer was altered
}
// remove variable from the cyclic stack
priorVariables.remove(priorVariables.size() - 1);
break;
}
}
}
}
}
if (top) {
return (altered ? 1 : 0);
}
return lengthChange;
}
/**
* Checks if the specified variable is already in the stack (list) of variables.
*
* @param varName the variable name to check
* @param priorVariables the list of prior variables
*/
private void checkCyclicSubstitution(String varName, List priorVariables) {
if (priorVariables.contains(varName) == false) {
return;
}
StrBuilder buf = new StrBuilder(256);
buf.append("Infinite loop in property interpolation of ");
buf.append(priorVariables.remove(0));
buf.append(": ");
buf.appendWithSeparators(priorVariables, "->");
throw new IllegalStateException(buf.toString());
}
/**
* Internal method that resolves the value of a variable.
*
* Most users of this class do not need to call this method. This method is
* called automatically by the substitution process.
*
* Writers of subclasses can override this method if they need to alter
* how each substitution occurs. The method is passed the variable's name
* and must return the corresponding value. This implementation uses the
* {@link #getVariableResolver()} with the variable's name as the key.
*
* @param variableName the name of the variable, not null
* @param buf the buffer where the substitution is occurring, not null
* @param startPos the start position of the variable including the prefix, valid
* @param endPos the end position of the variable including the suffix, valid
* @return the variable's value or null if the variable is unknown
*/
protected String resolveVariable(String variableName, StrBuilder buf, int startPos, int endPos) {
StrLookup resolver = getVariableResolver();
if (resolver == null) {
return null;
}
return resolver.lookup(variableName);
}
// Escape
//-----------------------------------------------------------------------
/**
* Returns the escape character.
*
* @return the character used for escaping variable references
*/
public char getEscapeChar() {
return this.escapeChar;
}
/**
* Sets the escape character.
* If this character is placed before a variable reference in the source
* text, this variable will be ignored.
*
* @param escapeCharacter the escape character (0 for disabling escaping)
*/
public void setEscapeChar(char escapeCharacter) {
this.escapeChar = escapeCharacter;
}
// Prefix
//-----------------------------------------------------------------------
/**
* Gets the variable prefix matcher currently in use.
*
* The variable prefix is the characer or characters that identify the
* start of a variable. This prefix is expressed in terms of a matcher
* allowing advanced prefix matches.
*
* @return the prefix matcher in use
*/
public StrMatcher getVariablePrefixMatcher() {
return prefixMatcher;
}
/**
* Sets the variable prefix matcher currently in use.
*
* The variable prefix is the characer or characters that identify the
* start of a variable. This prefix is expressed in terms of a matcher
* allowing advanced prefix matches.
*
* @param prefixMatcher the prefix matcher to use, null ignored
* @return this, to enable chaining
* @throws IllegalArgumentException if the prefix matcher is null
*/
public StrSubstitutor setVariablePrefixMatcher(StrMatcher prefixMatcher) {
if (prefixMatcher == null) {
throw new IllegalArgumentException("Variable prefix matcher must not be null!");
}
this.prefixMatcher = prefixMatcher;
return this;
}
/**
* Sets the variable prefix to use.
*
* The variable prefix is the characer or characters that identify the
* start of a variable. This method allows a single character prefix to
* be easily set.
*
* @param prefix the prefix character to use
* @return this, to enable chaining
*/
public StrSubstitutor setVariablePrefix(char prefix) {
return setVariablePrefixMatcher(StrMatcher.charMatcher(prefix));
}
/**
* Sets the variable prefix to use.
*
* The variable prefix is the characer or characters that identify the
* start of a variable. This method allows a string prefix to be easily set.
*
* @param prefix the prefix for variables, not null
* @return this, to enable chaining
* @throws IllegalArgumentException if the prefix is null
*/
public StrSubstitutor setVariablePrefix(String prefix) {
if (prefix == null) {
throw new IllegalArgumentException("Variable prefix must not be null!");
}
return setVariablePrefixMatcher(StrMatcher.stringMatcher(prefix));
}
// Suffix
//-----------------------------------------------------------------------
/**
* Gets the variable suffix matcher currently in use.
*
* The variable suffix is the characer or characters that identify the
* end of a variable. This suffix is expressed in terms of a matcher
* allowing advanced suffix matches.
*
* @return the suffix matcher in use
*/
public StrMatcher getVariableSuffixMatcher() {
return suffixMatcher;
}
/**
* Sets the variable suffix matcher currently in use.
*
* The variable suffix is the characer or characters that identify the
* end of a variable. This suffix is expressed in terms of a matcher
* allowing advanced suffix matches.
*
* @param suffixMatcher the suffix matcher to use, null ignored
* @return this, to enable chaining
* @throws IllegalArgumentException if the suffix matcher is null
*/
public StrSubstitutor setVariableSuffixMatcher(StrMatcher suffixMatcher) {
if (suffixMatcher == null) {
throw new IllegalArgumentException("Variable suffix matcher must not be null!");
}
this.suffixMatcher = suffixMatcher;
return this;
}
/**
* Sets the variable suffix to use.
*
* The variable suffix is the characer or characters that identify the
* end of a variable. This method allows a single character suffix to
* be easily set.
*
* @param suffix the suffix character to use
* @return this, to enable chaining
*/
public StrSubstitutor setVariableSuffix(char suffix) {
return setVariableSuffixMatcher(StrMatcher.charMatcher(suffix));
}
/**
* Sets the variable suffix to use.
*
* The variable suffix is the characer or characters that identify the
* end of a variable. This method allows a string suffix to be easily set.
*
* @param suffix the suffix for variables, not null
* @return this, to enable chaining
* @throws IllegalArgumentException if the suffix is null
*/
public StrSubstitutor setVariableSuffix(String suffix) {
if (suffix == null) {
throw new IllegalArgumentException("Variable suffix must not be null!");
}
return setVariableSuffixMatcher(StrMatcher.stringMatcher(suffix));
}
// Resolver
//-----------------------------------------------------------------------
/**
* Gets the VariableResolver that is used to lookup variables.
*
* @return the VariableResolver
*/
public StrLookup getVariableResolver() {
return this.variableResolver;
}
/**
* Sets the VariableResolver that is used to lookup variables.
*
* @param variableResolver the VariableResolver
*/
public void setVariableResolver(StrLookup variableResolver) {
this.variableResolver = variableResolver;
}
}