Question on adding Xpath2.0 functions to Xalan2.6?

[Andrew Fielden <af...@tibco.com>]

Does anyone have experience of registering a custom function with Xalan?
I've looked at the examples on the apache website, but none address my
specific situation.

I'm using a stylesheet that was created for a custom xslt engine which
makes use of Xpath2.0 features, specifically the exists() function. 

We're now using the stylesheet with Xalan 2.6, which does not support
Xpath2.0. 

So I need to write a custom exists() function and register it
programatically in Java with Xalan. 

I've consulted the Apache website, and the examples typically involve
creating extension functions in a custom namespace, then modifying the
stylesheet to use these functions. In my case I am not able to modify
the stylesheet. 

My question is can anyone give advice on how I provide and register an
implementation of  exists() with the Xalan engine so it can process my
stylesheet? This new function must exist in the default namespace i.e.
I'm not able to add extra namespace tags to the stylesheet. The
following stylesheet has to work with Xalan Java 2.6


<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:fn="http://www.w3.org/2005/02/xpath-functions"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:ns="http://www.tibco.com/xmlns/ae2xsd/2002/05/ae/ADB/ActiveDatabas
eAdapterConfiguration" version="1.0" exclude-result-prefixes="xsi xsd">
    <xsl:output method="xml"/>
    <xsl:param name="SW_FIELDS"/>
    <xsl:template match="/">
        <ns:P__CUSTOMER__IP>
            <CUSTID>
                <xsl:choose>
                    <xsl:when
test="exists($SW_FIELDS/user_fields/PARAM1)">
                        <xsl:value-of
select="$SW_FIELDS/user_fields/PARAM1"/>
                    </xsl:when>
                    <xsl:otherwise>
                        <xsl:attribute
name="xsi:nil">true</xsl:attribute>
                    </xsl:otherwise>
                </xsl:choose>
            </CUSTID>
        </ns:P__CUSTOMER__IP>
    </xsl:template>
</xsl:stylesheet>


Any examples would be very useful. 

Thanks for any help. 
Andrew.