* @param resolvable Resolvable used to resolve properties (e.g. filename)
* @return Result as string
*/
private static String evaluateString(final String expressionString, final Resolvable resolvable) {
String result = null;
ExpressionParser expressionParser = ExpressionParser.getInstance();
try {
EvaluableExpression expression = (EvaluableExpression) expressionParser.parse(expressionString);
ExpressionQueryRequest expressionQueryRequest = new ExpressionQueryRequest(
new PropertyResolver(resolvable), new HashMap<Object, Object>(0));
result = (String) expression.evaluate(expressionQueryRequest, ExpressionEvaluator.OBJECTTYPE_STRING);
} catch (ExpressionParserException e) {
LOGGER.error("Error while evaluating the expression (" + expressionString + ") with the base resolvable ("