/**
* Internal method that resolves the value of a variable.
*
* <p>Most users of this class do not need to call this method. This method is called
* automatically by the substitution process.
*
* <p>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 <b>null</b> if the variable is unknown
*/
protected String resolveVariable(
final String variableName, final StrBuilder buf, final int startPos, final int endPos) {
final StrLookup<?> resolver = getVariableResolver();
if (resolver == null) {
return null;
}
return resolver.lookup(variableName);
}
