/**
   * Handle attribute node during validation.
   *
   * @param receivedElement
   * @param receivedAttribute
   * @param sourceElement
   * @param validationContext
   */
  private void doAttribute(
      Node receivedElement,
      Node receivedAttribute,
      Node sourceElement,
      XmlMessageValidationContext validationContext,
      NamespaceContext namespaceContext,
      TestContext context) {
    if (receivedAttribute.getNodeName().startsWith(XMLConstants.XMLNS_ATTRIBUTE)) {
      return;
    }

    String receivedAttributeName = receivedAttribute.getLocalName();

    if (log.isDebugEnabled()) {
      log.debug(
          "Validating attribute: "
              + receivedAttributeName
              + " ("
              + receivedAttribute.getNamespaceURI()
              + ")");
    }

    NamedNodeMap sourceAttributes = sourceElement.getAttributes();
    Node sourceAttribute =
        sourceAttributes.getNamedItemNS(receivedAttribute.getNamespaceURI(), receivedAttributeName);

    Assert.isTrue(
        sourceAttribute != null,
        "Attribute validation failed for element '"
            + receivedElement.getLocalName()
            + "', unknown attribute "
            + receivedAttributeName
            + " ("
            + receivedAttribute.getNamespaceURI()
            + ")");

    if (XmlValidationUtils.isAttributeIgnored(
        receivedElement,
        receivedAttribute,
        sourceAttribute,
        validationContext.getIgnoreExpressions(),
        namespaceContext)) {
      return;
    }

    String receivedValue = receivedAttribute.getNodeValue();
    String sourceValue = sourceAttribute.getNodeValue();
    if (isValidationMatcherExpression(sourceAttribute)) {
      ValidationMatcherUtils.resolveValidationMatcher(
          sourceAttribute.getNodeName(),
          receivedAttribute.getNodeValue().trim(),
          sourceAttribute.getNodeValue().trim(),
          context);
    } else if (receivedValue.contains(":") && sourceValue.contains(":")) {
      doNamespaceQualifiedAttributeValidation(
          receivedElement, receivedAttribute, sourceElement, sourceAttribute);
    } else {
      Assert.isTrue(
          receivedValue.equals(sourceValue),
          ValidationUtils.buildValueMismatchErrorMessage(
              "Values not equal for attribute '" + receivedAttributeName + "'",
              sourceValue,
              receivedValue));
    }

    if (log.isDebugEnabled()) {
      log.debug("Attribute '" + receivedAttributeName + "'='" + receivedValue + "': OK");
    }
  }