XSLT transformation passing parameters - xslt

Question

I am trying to pass parameters during an XSLT transformation. Here is the xsl stylesheet.
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:param name="param1" select="'defaultval1'" />
<xsl:param name="param2" select="'defaultval2'" />
<xsl:template match="/">
<xslttest>
<tagg param1="{$param1}"><xsl:value-of select="$param2" /></tagg>
</xslttest>
</xsl:template>
</xsl:stylesheet>
The following in the java code.
File xsltFile = new File("template.xsl");
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document stylesheet = builder.parse("template.xsl");
TransformerFactory transformerFactory = TransformerFactory.newInstance();
Transformer xsltTransformer = transformerFactory.newTransformer(new DOMSource(stylesheet));
//Transformer xsltTransformer = transformerFactory.newTransformer(new StreamSource(xsltFile));
xsltTransformer.setParameter("param1", "value1");
xsltTransformer.setParameter("param2", "value2");
StreamResult result = new StreamResult(System.out);
xsltTransformer.transform(new DOMSource(builder.newDocument()), result);
I get following errors:-
ERROR: 'Variable or parameter 'param1' is undefined.'
FATAL ERROR: 'Could not compile stylesheet'
However, if i use the following line to create the transformer everything works fine.
Transformer xsltTransformer = transformerFactory.newTransformer(new StreamSource(xsltFile));
Q1. I just wanted to know whats wrong in using a DOMSource in creating a Transformer.
Q2. Is this one of the ideal ways to substitute values for placeholders in an xml document? If my placeholders were in a source xml document is there any (straightforward) way to substitute them using style sheets (and passing parameters)?

Answer 1

Q1: This is a namespace awareness problem. You need to make the DocumentBuilderFactory namespace aware:
factory.setNamespaceAware(true);
Q2: There are several ways to get the values from an external xml file. One way to do this is with the document function and a top level variable in the document:
<!-- Loads a map relative to the template. -->
<xsl:variable name="map" select="document('map.xml')"/>
Then you can select the values out of the map. For instance, if map.xml was defined as:
<?xml version="1.0" encoding="UTF-8"?>
<mappings>
<mapping key="value1">value2</mapping>
</mappings>
You could remove the second parameter from your template, then look up the value using this line:
<tagg param1="{$param1}"><xsl:value-of select="$map/mappings/mapping[#key=$param1]"/></tagg>
Be aware that using relative document URIs will require that the stylesheet has a system id specified, so you will need to update the way you create your DOMSource:
DOMSource source = new DOMSource();
source.setNode(stylesheet);
source.setSystemId(xsltFile.toURL().toString());
In general, I suggest looking at all of the options that are available in Java's XML APIs. Assume that all of the features available are set wrong for what you are trying to do. I also suggest reading the XML Information Set. That specification will give you all of the definitions that the API authors are using.