Transform XML with XSLT in Java using DOM

Question

I've been looking around everywhere for Java samples to transform an XML document with an XSLT. I've found several samples using new File("path/to/file.xml") to load in the XML and the XSLT and those work great. My problem is that I'm trying to use this in a new method that will accept two org.w3c.dom.Document objects. As soon as I replace the StreamSource used to load in the XSLT with a DOMSource the result of my call is then the XSLT instead of the transformed XML.

Working code from How to call XSL template from java code?:

Source xmlInput = new StreamSource(new File("c:/path/to/input.xml"));
Source xsl = new StreamSource(new File("c:/path/to/file.xsl"));
Result xmlOutput = new StreamResult(new File("c:/path/to/output.xml"));

try {
    Transformer transformer =     TransformerFactory.newInstance().newTransformer(xsl);
    transformer.transform(xmlInput, xmlOutput);
} catch (TransformerException e) {
    // Handle.
}

My code:

public static Document transformXML(Document xml, Document xslt) throws TransformerException, UnsupportedEncodingException, SAXException, IOException, ParserConfigurationException, FactoryConfigurationError{

    Source xmlSource = new DOMSource(xml);
    Source xsltSource = new DOMSource(xslt);
    StreamResult result = new StreamResult(new StringWriter());

    // the factory pattern supports different XSLT processors
    TransformerFactory transFact =
            TransformerFactory.newInstance();
    Transformer trans = transFact.newTransformer(xsltSource);

    trans.transform(xmlSource, result);

    Document resultDoc = DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(new ByteArrayInputStream(result.getWriter().toString().getBytes("utf-8")));

    return resultDoc;
}

My result document is then the XSLT instead of the XML. What am I doing wrong with the DOMSource?

Are the DOM trees you feed to the transformer built with a namespace aware document builder? If you want a Document node as the result, why don't you simply use DOMResult result = new DOMResult(); trans.transform(xmlSource, result); Document resultDoc = (Document)result.getNode();? — Martin Honnen
– Martin Honnen, Commented Oct 9, 2015 at 17:47
@MartinHonnen Very good point. I've updated the code. Now for some awful reason, my resultDoc is still the XSLT. It's like the transformer switches them up!? — GuillaumeCleme
– GuillaumeCleme, Commented Oct 9, 2015 at 19:29

Martin Honnen · Accepted Answer · 2015-10-10 12:39:56Z

XSLT and XPath only make sense with a namespace aware DOM implementation and DOM tree, that is why I asked "Are the DOM trees you feed to the transformer built with a namespace aware document builder?" in my comment.

As far as I have tested with Oracle Java 1.8, when a not namespace-aware DocumentBuilderFactory and the built-in Transformer is used, your method returns the stylesheet code. However as soon as I change the DocumentBuilderFactory to be namespace aware, the result is as intended.

Here is the working sample:

package domsourcetest1;

import java.io.IOException;
import javax.xml.parsers.FactoryConfigurationError;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMResult;
import javax.xml.transform.dom.DOMSource;
import org.w3c.dom.Document;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.xml.sax.SAXException;
import org.w3c.dom.DOMImplementation;
import org.w3c.dom.ls.DOMImplementationLS;
import org.w3c.dom.ls.LSSerializer;

/**
 *
 * @author Martin Honnen
 */
public class DOMSourceTest1 {


    public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException, TransformerException {
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        dbf.setNamespaceAware(true);
        DocumentBuilder db = dbf.newDocumentBuilder();
        Document xslt = db.parse("sheet1.xsl");
        Document xml = db.newDocument();
        xml.appendChild(xml.createElementNS(null, "root"));
        Document result = transformXML(xml, xslt);
        System.out.println(result.getDocumentElement().getTextContent());
        LSSerializer serializer = ((DOMImplementationLS) xml.getImplementation()).createLSSerializer();
        System.out.println(serializer.writeToString(result));
    }

    public static Document transformXML(Document xml, Document xslt) throws TransformerException, ParserConfigurationException, FactoryConfigurationError {

        Source xmlSource = new DOMSource(xml);
        Source xsltSource = new DOMSource(xslt);
        DOMResult result = new DOMResult();

        // the factory pattern supports different XSLT processors
        TransformerFactory transFact
                = TransformerFactory.newInstance();
        Transformer trans = transFact.newTransformer(xsltSource);

        trans.transform(xmlSource, result);

        Document resultDoc = (Document) result.getNode();

        return resultDoc;
    }
}

The sample stylesheet simply outputs information about the XSLT processor:

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
    <xsl:template match="/">
        <debug>
            <xsl:value-of select="system-property('xsl:vendor')"/>
        </debug>
    </xsl:template>

</xsl:stylesheet>

Output of the program is

Apache Software Foundation (Xalan XSLTC)
<?xml version="1.0" encoding="UTF-16"?>
<debug>Apache Software Foundation (Xalan XSLTC)</debug>

Now when I comment out //dbf.setNamespaceAware(true); in the main method the result is

<?xml version="1.0" encoding="UTF-16"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"><xsl:template match="/"><debug><xsl:value-of select="system-property('xsl:vendor')"/></debug></xsl:template></xsl:stylesheet>

meaning the result is indeed the stylesheet document. That is obviously a bug or at least a quirk with the built-in Xalan Transformer, when I put Saxon 6.5.5 on the class path the problem does not occur, nor does it occur with Saxon 9.6 on the class path.

In general, however, I don't think you will get meaningful results when using XSLT or XPath with not namespace aware DOM trees. See also the DOM2DOM sample in the Xalan release http://svn.apache.org/viewvc/xalan/java/tags/xalan-j_2_7_2/samples/DOM2DOM/DOM2DOM.java?revision=1695338&view=markup which says

  // And setNamespaceAware, which is required when parsing xsl files
  dFactory.setNamespaceAware(true);

You sir are awesome! dFactory.setNamespaceAware(true); was indeed all I needed. This is very interesting behavior but I won't fight it. @MartinHonnen

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