I'm trying to figure out how XPath expressions work, and how I can use them
to extract data into a particular format.  I can extract the data I want
using an XPath expression, but not with an XSLT stylesheet.  Here's the
Java/XPath I'm using:


import java.io.*;
import javax.xml.parsers.*;
import org.w3c.dom.*;
import org.xml.sax.SAXException;
import javax.xml.xpath.*;

public class XpathEval
{
    public static void main(String []args)
    {
        try {
            XpathEval loader = new XpathEval("src.xml");
            loader.evaluateXpath();
        }
        catch(Exception e) {
            System.out.println(e);
        }
    }


    public XpathEval(String filename)
        throws javax.xml.parsers.ParserConfigurationException,
               SAXException,
               IOException
    {
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        DocumentBuilder db = dbf.newDocumentBuilder();
        m_doc = db.parse(new File(filename));
    }

    public void evaluateXpath(String xpathExpr)
        throws XPathExpressionException
    {
        XPathFactory f = XPathFactory.newInstance();
        XPath p = f.newXPath("/nuc2/Exer/ExerciseNickname");
        NodeList nl = (NodeList)p.evaluate(xpathExpr, m_doc,
XPathConstants.NODESET);
        for (int i = 0; i < nl.getLength(); i++)
            System.out.println(nl.item(i).getNodeName() + " -> " +
nl.item(i).getTextContent());
    }

    private Document m_doc;
}


However, if I try to extract & format the data via xsltproc it doesn't
extract the data.  Here's the command I use:

    xsltproc xsltStyleSheet.xsl src.xml

with the following for xsltStyleSheet.xsl:

  <?xml version="1.0" encoding="UTF-8"?>

  <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
   version="1.0">

    <xsl:template match="/">
    EXER/<xsl:value-of
select="/nuc2/Exer/ExerciseNickname"/>/NICK:<xsl:value-of
select="/nuc2/Exer/ExerciseAdditionalIdentifier"/>//
    </xsl:template>

  </xsl:stylesheet>



Instead of printing out what I expect (the odd format is a requirement for
what I'm trying to convert it to):

    EXER/pushups/NICK:whatever//

it prints this:

    EXER//NICK://

If I change the XPath expression in my XSLT stylesheet to
select="//ExerciseNickname" then it works.  But in the full XML file there
are places where that won't work - there's /a/b/fieldname
and /x/y/fieldname and I want exactly one of them.  I suppose I could make
that work, but I'd like to know what I'm doing wrong.

The XML source (src.xml, above) is:

<ns2:nuc2 xsi:schemaLocation="nuc2.xsd" xmlns:ns1="Exer_Sets"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns2="nuc2">
   
  <ns1:Exer SetSequence="1" SetDescription="Exercise Identification">
    <ExerciseNickname>pushups</ExerciseNickname>
    <ExerciseAdditionalIdentifier>whatever</ExerciseAdditionalIdentifier>
  </ns1:Exer>

</ns2:nuc2>


I'm giving it the same XPath expression in both cases
("/nuc2/Exer/ExerciseNickname") - one finds what I'm looking for, the other
doesn't.  I'm using Java 1.6.0_05 on Fedora 8.  xsltproc comes from the
libxslt package, version 1.1.24.

Any clues?

thanks!

-- 
Al Dunstan, Software Engineer
OptiMetrics, Inc.
3115 Professional Drive
Ann Arbor, MI  48104-5131