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Posted to dev@xalan.apache.org by Henry Zongaro <zo...@ca.ibm.com> on 2006/10/17 20:53:35 UTC
Select-like attributes in extension elements?
Hello.
Somebody contacted me directly today about a problem they were having with
evaluating an XPath expression in an attribute of an extension element.
(This person is using Xalan-J Interpretive.) I pointed out the
ElemExtensionCall.getAttribute method,[1] which allows you to treat an
attribute in an extension element as an AVT and get the effective value of
the attribute.
He seemed happy with that, but wanted to know how to treat an attribute as
an XPath expression which could be evaluated to a node set. So far as I
can tell, there is no simple API that exists. Instead users have had to
do things along the lines of what Simon Kitching describes in [2]. Is
anybody aware of a simpler way of doing this? If not, is anybody aware of
whether the project has ever received a request for a new feature along
these lines?
Thanks,
Henry
[1]
http://xml.apache.org/xalan-j/apidocs/org/apache/xalan/templates/ElemExtensionCall.html#getAttribute(java.lang.String,%20org.w3c.dom.Node,%20org.apache.xalan.transformer.TransformerImpl)
[2] http://marc.theaimsgroup.com/?l=xalan-j-users&m=102400418815043&w=2
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Henry Zongaro XSLT Processors Development
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Re: Select-like attributes in extension elements?
Posted by Henry Zongaro <zo...@ca.ibm.com>.
Hi, Joe.
keshlam@us.ibm.com wrote on 2006-10-17 04:53:44 PM:
> Just making sure I understand the question: Is the user looking for
> arbitrary XPath interpretation, similar to
> http://www.exslt.org/dyn/
> or are they specifically looking for the equivalent of select?
The equivalent of select. It just surprised me that there seemed to be
convenient APIs for treating the value of an attribute of an extension
element as a fixed string or as AVT, but not as a single XPath expression
returning its "natural" value rather than being always cast to a string.
> Of course all of this is going to be emphatically nonportable to
> other processors, which makes me a bit nervous about investing too
> much effort in it.
Agreed. This was more of a "do we already have" question on my part,
rather than a recommendation that we should add such a facility.
Thanks,
Henry
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Re: Select-like attributes in extension elements?
Posted by ke...@us.ibm.com.
Just making sure I understand the question: Is the user looking for
arbitrary XPath interpretation, similar to
http://www.exslt.org/dyn/
or are they specifically looking for the equivalent of select?
We do have an implementation of exslt:dyn, though of course it works only
in interpretive mode and any interactive XPath evaluator would be likewise
constrained. If someone's looking for an "API", adding one to that code is
the best solution I can think of offhand.
Something more select-like (with hardcoded path), theoretically might be
implementable even in compiled mode, if there was some way for us to
recognize that this particular attribute was supposed to be a nodeset
retrieval request. I guess, since the extension behivor is specific to the
implementation, we could reserve a specific namespaced attribute (or
namespace alone, so multiple selects could exist?) to cue the processor
that this is our intent. This would be roughly equivalent to setting a
variable to a nodeset using select, then passing that variable into the
extension; just a bit less verbose.
Of course all of this is going to be emphatically nonportable to other
processors, which makes me a bit nervous about investing too much effort in
it.
______________________________________
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