xsltproc vs XPath evaluate() method

Question posted by: A. W. Dunstan (Guest) on June 27th, 2008 07:07 PM

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

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