code: private static String getAttributeValue(String attribute, Element element,
  			ParserContext parserContext) {
  		String attributeValue = element.getAttribute(attribute);
  		if (!StringUtils.hasText(attributeValue)) {
  			parserContext.getReaderContext().error(
  					"The '" + attribute + "' attribute must not be empty", element);
  		}
  		return attributeValue;
  	}
docs: Returns the attribute value and reports an error if the attribute value is null or
  empty. Normally the reported error leads into an exception which will be thrown
  through the {@link org.springframework.beans.factory.parsing.ProblemReporter}
  implementation.
  @param attribute - The name of the attribute which will be valuated
  @param element - The element that contains the attribute
  @param parserContext - The parser context used to report errors
  @return - The attribute value