public void init(XMLStructure parent, XMLCryptoContext context)
     throws InvalidAlgorithmParameterException {
   super.init(parent, context);
   try {
     unmarshalParams(DOMUtils.getFirstChildElement(transformElem));
   } catch (MarshalException me) {
     throw new InvalidAlgorithmParameterException(me);
   }
 }
  /**
   * Creates a <code>DOMReference</code> from an element.
   *
   * @param refElem a Reference element
   */
  public DOMReference(Element refElem, XMLCryptoContext context) throws MarshalException {
    // unmarshal Transforms, if specified
    Element nextSibling = DOMUtils.getFirstChildElement(refElem);
    List transforms = new ArrayList(5);
    if (nextSibling.getLocalName().equals("Transforms")) {
      Element transformElem = DOMUtils.getFirstChildElement(nextSibling);
      while (transformElem != null) {
        transforms.add(new DOMTransform(transformElem, context));
        transformElem = DOMUtils.getNextSiblingElement(transformElem);
      }
      nextSibling = DOMUtils.getNextSiblingElement(nextSibling);
    }

    // unmarshal DigestMethod
    Element dmElem = nextSibling;
    this.digestMethod = DOMDigestMethod.unmarshal(dmElem);

    // unmarshal DigestValue
    try {
      Element dvElem = DOMUtils.getNextSiblingElement(dmElem);
      this.digestValue = Base64.decode(dvElem);
    } catch (Base64DecodingException bde) {
      throw new MarshalException(bde);
    }

    // unmarshal attributes
    this.uri = DOMUtils.getAttributeValue(refElem, "URI");
    this.id = DOMUtils.getAttributeValue(refElem, "Id");

    this.type = DOMUtils.getAttributeValue(refElem, "Type");
    this.here = refElem.getAttributeNodeNS(null, "URI");
    this.refElem = refElem;

    if (transforms.isEmpty()) {
      this.transforms = Collections.EMPTY_LIST;
    } else {
      this.transforms = Collections.unmodifiableList(transforms);
    }
    this.appliedTransforms = Collections.EMPTY_LIST;
    this.allTransforms = transforms;
    this.appliedTransformData = null;
  }