code: @Override
  	public String initValuesImpl(final FieldCase c) {
  		if (c == FieldCase.NULL) {
  			return null;
  		}
  		String value = source.initValues(c);
  		if (value == null) {
  			return defaultValue;
  		}
  		return value;
  	}
docs: Calls {@link #initValues(FieldCase)} on the source constraint. If this returns {@code null}
  the defaulValue will be returned