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From "Hunsberger, Peter" <>
Subject RE: ServerPageAction: XMLFragment reuse in XSL transformer
Date Mon, 21 Oct 2002 13:56:00 GMT
That should work.  I don't know if it is much (any?) more efficient than
using aggregation...

-----Original Message-----
From: Christian Kurz []
Sent: Saturday, October 19, 2002 4:53 AM
Subject: Re: ServerPageAction: XMLFragment reuse in XSL transformer

I'll try to implement a pipeline similar to this:
FileGenerator        -> "MyFilterTransformer" -> other steps
The FileGenerator will read the big document and is cacheable.
MyFilterTransformer will use the XMLFragment from the session to forward
only a small portion of the events from the generator, following your idea.
MyFilterTransformer is the first component in the pipeline, which is NOT
cacheable, as it returns different data on every request.
To my understanding cocoon's caching strategy should cache the pipeline as
far as possible. In this particular case only including the FileGenerator:
"The keys of all cacheable components are chained, and together they build
the cache key. The request is processed, and the document is built. The
cache stores the result of the _last_ component, indicating cacheablility.
The next time this document is requested, the key is built, and the cached
content is fetched from the cache.
Next, the cache asks all components of the event pipeline, if their input
has changed since the time the content was cached. For example, the
generator checks this by looking at the last modification date of the xml
document, the xslt transformer checks the date of the stylesheet, and so on.
Only if all state that the content is still valid it is used from the cache.
Otherwise, the document is generated from scratch. So the event pipeline
tries to cache as much of the XML processing pipeline as possible."
from New Riders, Cocoon: Building XML Applications by Matthew Langham and
Carsten Ziegeler, p. 182.

----- Original Message ----- 
From: Hunsberger, Peter <>  
To: '' <mailto:''>  
Sent: Friday, October 18, 2002 4:23 PM
Subject: RE: ServerPageAction: XMLFragment reuse in XSL transformer

Well, obviously, it something changes on every request then, by definition,
it isn't cacheable.  However, I believe, with aggregation, only the
components that are marked as invalidated in the cache are rebuilt on a new
request; the rest of the data stays in it's respective cache.   This does
mean that the aggregated document is rebuilt each time (I have no idea what
the impact of that would be).  But the "large" document source would stay
not be retrieved from scratch.
Perhaps using the document function as Olivier would avoid this.  At one
point document did not check cache validity at all and you would only get a
newer version of the data if the main data was invalidated in cache. I think
this has been fixed in 2.0.3.  The problem is how to get the URI resolve for
the document function to fund the data in session.  Someone else will have
to tell you how to do that (and if it's even possible)...
 -----Original Message-----
From: Christian Kurz []
Sent: Friday, October 18, 2002 1:42 AM
Subject: Re: ServerPageAction: XMLFragment reuse in XSL transformer

Thank you very much for the quick feed-back! The idea sounds great and is a
lot cleaner, than fiddling something in some XSL extension.
I am not sure about the cachaebility: the XMLFragment specifying, which
nodes to filter from the big input document, changes everytime, so Cocoon
would need to parse the source file on every request (, if my understanding
is right).
If I'd slidely change your approach to implementing the same approach into a
transformer component. This transformer component will not be cacheable, but
at least the generator in front of it would be.
Thanks again,
BTW, thanks also for the code snippet. It helps a lot, as soon as it comes
to thinks like the ObjectModel, I start feeling uncomfortable.
----- Original Message ----- 

From: Hunsberger, Peter <>  
To: '' <mailto:''>  
Sent: Thursday, October 17, 2002 6:46 PM
Subject: RE: ServerPageAction: XMLFragment reuse in XSL transformer

There's probably about half a dozen ways to do this.  Perhaps one of the
simplest is just to create your own caching generator and use aggregation
(with any other XML you may need) in the pipeline.
In the generator you'll need to implement the setup method to see the
objectModel, something like the following:
private gunk mySessionData = null;
public void setup( SourceResolver resolver, Map objectModel, String src,
Parameters parms )
      throws ProcessingException,  SAXException,   IOException
     if (mySessionData == null ) {
          super.setup( resolver, objectModel, src, parms );
          Request request =
          Session session = request.getSession(false);
          if (session != null)  {
            // save a pointer to your session data for use in the generate
            mySessionData = ....
Now in your generate method just pick up whatever data hangs off of
"mySessionData" and away you go
-----Original Message-----
From: Christian Kurz []
Sent: Thursday, October 17, 2002 11:26 AM
Subject: ServerPageAction: XMLFragment reuse in XSL transformer

Hello cocoon-users,

I need to generate some tiny XML elements (XMLFragment) within a
ServerPageAction and I would like to use this XMLFragment later on in an XSL
transformer, that is fed by an xml generator. The XMLFragment captured in
the ServerPageAction is basically saying, which nodes are to be returned
from the big input document.
>From some other message in this group I have understood, that passing
objects is only possible through session or request objects, but not through
sitemap variables. I don't like to use a request generator as the starting
point of the pipeline, as I'd loose cacheability at a very early step in the
pipeline. With a quite big xml input document, this does not seem a good
idea to me.
So I am currently struggling how to get a piece of XML, that is attached to
a session or request object, into the xsl transformer. Has anybody tried
this before e.g. using an XSL extension?
Any help or hints appreciated!
Thank you in advance,

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