XSLT adding your own functions

[Duane Morin]

Is this normal use of XSLT? At the top of our XSL file we have:

<xsl:stylesheet ...
xmlns:nl="http://www.jclark.com/xt/java/com.company.package.ProcessXML"> ....

Then within the XSL itself we call:

<xsl:value-of select="nl:generate-url('x', 'y', 'z')" />

Where generate-url is actually defined in ProcessXML.java:

public static String generateUrl (String x, String y, String z) { ...
}

This works just fine when I'm performing the XSL transformation within my own Java app that has access to the ProcessXML class. However, it completely ruins my ability to use an XSL editor or do any type of external transformation which aborts with an exception about not being able to find the generate-url function.

So my question, since I didn't write this code , is this standard procedure for extending XSL to do what you want? If so, is there something that I'm missing which would enable a standalone XSL transformation engine (such as might be found in an IDE) to recognize the functions I added? Is there a way that I could write some sort of stub/dummy plugin for generateUrl that would do nothing, but at least keep the transform from failing?

This approach has served us fine in a world where the Java guys also did all the XSL coding and so always worked within the scope of a Java app, but we're getting to a point where we'll have dedicated content people and I'd like them to be able to use an XSL editor of their choice. Right now the only option is "Edit XSL, check in to source control, request a rebuild (since they cannot build the product on their workstations), look at results, repeat."

Thanks!

 

[Duane Morin]

Ok, with a little extra reading let me followup my own question with some more intelligent ones. Now that I discovered that this trick is called an "extension function" it was much easier to find info .

* Is the way we're doing it specific to JClark's parser, such that switching over to another one might still break me even if I was doing everything else right?

* Where exactly do I *put* my extension functions so that the XSLT parser can find them? That's the part I can't seem to locate. Obviously they are not at www.jclark.com. They're not at any http resolvable location, actually - but I dont think they have to be. When the class in question exists in the same jar as the app doing a transform, then it works fine.

Hope those are better questions . Thanks!

Duane

 

[Patrick TJ McPhee]

% * Is the way we're doing it specific to JClark's parser, such that % switching over to another one might still break me even if I was doing % everything else right?

It seems like it. As a rule, if you need to use extension functions, I suggest using the ones from http://exslt.org where applicable, since they're the most widely supported. What gets supported and how to add new extensions is completely dependent on the xslt processor you're using, though.

You can use the function-available to test for the availability of an extension function

<xsl:choose>
<xsl:when test='function-available("nl:generate-url")'> <xsl:value-of select="nl:generate-url('x', 'y', 'z')" /> </xsl:when> <xsltherwise>
** url made up of x, y, and z **
</xsltherwise>
</xsl:choose>

 

[Duane Morin]

You can use the function-available to test for the availability of an extension function

Awesome - that's exactly what I needed! Thanks!!

Duane