iDOM
From Documentation
Package: org.zkoss.idom
An implementation of W3C DOM. It is inspired by JDOM[1] to have concrete classes for all XML objects, such as Element and Attribute. However, iDOM implements the W3C API, such as org.w3c.dom.Element. Thus, you could use iDOM seamlessly with XML utilities that only accept the W3C DOM.
A typical example is XSLT and XPath. You could use any of favorite XSL processor and XPath utilities with iDOM.