class ParameterRepositoryServiceImpl implements ParameterRepositoryService {

    @Override
    public String getSubParameterValueAsString(ParameterKey key, String subParameterName) {
        if (StringUtils.isBlank(subParameterName)) {
            throw new RiceIllegalArgumentException("subParameterName is blank");
        }

        Collection<String> values = getParameterValuesAsString(key);
        return getSubParameter(values, subParameterName);
    }

}