XSLT input parameter not picked up when Saxon is in use?

Question

I am passing a simple string parameter to my Saxon-driven XSLT, but it is not getting picked up.

Here's the XSL (min.xsl):

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                version="2.0">
    <xsl:template match="/">
        <xsl:param name="in"/>
        <Out>
            <xsl:choose>
                <xsl:when test="Val = $in">match!</xsl:when>
                <xsl:otherwise>
                    <xsl:value-of select="Val"/> != <xsl:value-of select="$in"/>
                </xsl:otherwise>
            </xsl:choose>
        </Out>
    </xsl:template>
</xsl:stylesheet>

Here's the code used to invoke the XSLT:

import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;
import java.io.FileInputStream;
import java.io.StringReader;

public class MinXSLT {
    public static void main(String[] args) throws Exception {
        try {
            Class.forName("net.sf.saxon.TransformerFactoryImpl");
            System.setProperty("javax.xml.transform.TransformerFactory", "net.sf.saxon.TransformerFactoryImpl");
            System.out.println("Plugged in Saxon");
        } catch (ClassNotFoundException ignore) {}

        final TransformerFactory transformerFactory = TransformerFactory.newInstance();
        Transformer e = transformerFactory.newTemplates(new StreamSource(new FileInputStream("src/test/resources/min.xsl"))).newTransformer();
        e.setParameter("in", "x");
        e.transform(new StreamSource(new StringReader("<Val>x</Val>")), new StreamResult(System.out));
    }
}

Here's the dependencies section of my pom.xml:

<dependencies>
    <dependency>
        <groupId>saxon</groupId>
        <artifactId>saxon-he</artifactId>
        <version>9.2</version>
    </dependency>
</dependencies>

Yup, just saxon-he.

Strangely, when I remove the Saxon dependency, the parameter gets picked up and I get the expected result:

<?xml version="1.0" encoding="UTF-8"?><Out>match!</Out>

But when Saxon is in use, I get the 'parameter mismatch' result with an empty string in place of the parameter value:

Plugged in Saxon
<?xml version="1.0" encoding="UTF-8"?><Out>x != </Out>

What is my crime here?

For the record, I tried using newer versions of Saxon (net.sf.saxon:Saxon-HE:9.7.x etc.), with the same result; however in the actual project I am stuck with saxon:saxon-he:9.2 so upgrading is not really an option.

Answer 1

You need to move the <xsl:param name="in"/> outside of any xsl:template to have it as a global parameter you can set before the transformation. xsl:params inside templates are not settable by the JAXP transformation API, in XSLT 3 with Saxon's API you could call a named template or function directly and set its parameters when doing so but your approach with applying templates to a Source in JAXP is not meant for that. Simply use a global parameter, i.e. move the xsl:param outside of any xsl:template and make it a child of xsl:stylesheet/xsl:transform.