Using XPath for DOM traversal

Question

This question falls into the category of 'I know it's possible, I just need to find the idom in Java'.
I'm coming from a MSFT world were the DOM-centric model of XML processing makes heavy use of XPATH for node selection. Basically using the method element.selectNodes(XPathExpresson) allows one to quickly extract the relevant subset of the parsed tree in the DOM as a nodeList. I've become accustomed to using XML for all strucutured storage that doesn't require a full database.
The W3C DOM Level 3 spec supports evaluateExpression() for this purpose, but I can't believe that Java developers are still using tree traversal waiting for the spec to be implemented. I suppose that I could use getNodesByTagName(), but this is a chainsaw, and I need a scalpel. Anyway, I'm trying to figure out how, exactly, this gets done in Java.
I figure the following are possibilities:
1) It's in JAXP and I missed it
2) One or more of the XML parsers supports XPATH as an extention
3) There's a common package that sits on top of the DOM Document.
4) There's a standard way to apply and XSLT methods to the DOM document
5) Something I've never thought of.
This is a generalized problem for me, so I can't rely on object serialization, Java-XML data mapping, etc. Any guidance would be greatly appreciated.

Answer 1

I've written a Config file reader for XML in java,
and it extracts values using XPath. This is
some of the code you'll need:
imports:
import javax.xml.transform.TransformerException;
import org.w3c.dom.*;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.apache.xerces.parsers.DOMParser;
import org.apache.xpath.XPathAPI;
import org.apache.xpath.objects.*;
Document doc=....;
* returns a single DOM Node from the config file.
public Node getNode(String xpath) throws ConfigException {
try {
return XPathAPI.selectSingleNode(doc, xpath);
} catch (TransformerException e) {
throw new ConfigException("Can't find '"+xpath+"' ("+e.getMessage()+")");