new NamespaceHelper(PageEnvelope.NAMESPACE, PageEnvelope.DEFAULT_PREFIX, doc);
Element documentElement = doc.getDocumentElement();
Element metaElement = namespaceHelper.getFirstChild(documentElement, META);
if (metaElement == null) {
metaElement = namespaceHelper.createElement(META);
Element[] children = namespaceHelper.getChildren(documentElement);
if (children.length == 0) {
documentElement.appendChild(metaElement);
} else {
documentElement.insertBefore(metaElement, children[0]);