Element root = document.getDocumentElement();
root.appendChild(sig.getElement());
XPathFactory xpf = XPathFactory.newInstance();
XPath xpath = xpf.newXPath();
xpath.setNamespaceContext(new DSNamespaceContext());
for (String localName : localNames) {
String expression = "//*[local-name()='" + localName + "']";
NodeList elementsToSign =
(NodeList) xpath.evaluate(expression, document, XPathConstants.NODESET);