[xsl] Writing extension functions (& elements)

[Jeni Tennison <mail at jenitennison dot com>]

I said:
> : Yes, but be aware that Javascript isn't incorporated into XSLT until
> : XSLT 1.1 or unless you're using MSXML. 

Eugene pointed out:
> The binding mechanism wasn't standardized in XSLT 1.0, same as Java,
> but there are several implementations besides MSXML... Unicorn XSLT
> processor has one, for example, and I believe Xalan does too.

Eugene's absolutely right, of course, although I can't see any way in
Unicorn XSLT to include Javascript *in the stylesheet itself* - I
think you have to import a script using obj:import (obj being bound to
http://www.unicorn-enterprises.com/XSLT/Extensions/ECMAScript/1.0) and
then can call a function in that script either with function syntax like
obj:call(object, function, arguments*) or with element syntax.  I'd be
pleased to be corrected - this is just what I've gathered from a quick
read of the documentation.

Xalan-Java has some Really Cool Stuff that enables you to define not
only your own functions, but also your own elements, actually within a
stylesheet. You can also use loads of different languages to define
them (though not, sadly, XSLT ;)

Using a Javascript function in XSLT when you're using Xalan involves
the same kind of preparatory steps as using msxsl:script:

(a) declaring the Xalan namespace (http://xml.apache.org/xslt) - for
some reason the Xalan documentation uses the prefix lxslt
(b) declaring your own namespace (e.g. http://www.foo.com/)
(c) declaring the namespace prefixes you use as extension element
prefixes

You need to use two extension elements to define functions when using
Xalan: lxslt:component and lxslt:script.  The equivalent of the
msxsl:script element:

<msxsl:script language="javascript"
              implements-prefix="foo">
   function retrieveData() {
      return true;
   }
</msxsl:script>

is:

<lxslt:component prefix="foo" functions="retrieveData">
   <lxslt:script lang="javascript">
      function retrieveData() {
         return true;
      }
   </lxslt:script>
</lxslt:component>

While msxsl:script will disappear when XSLT 1.1 is finalised and
supported, it looks as though lxslt:component and lxslt:script will
still have a place because they allow you to write your own extension
elements as well.  Does anyone have any experience with writing
extension elements in Xalan that they could share?

Cheers,

Jeni

---
Jeni Tennison
http://www.jenitennison.com/



 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list