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From Mariano Kamp <mk...@codamax.com>
Subject Re: Why does a Serializer doesn't have a setup method? Was:Re: Cocoon Contracts (was Re: Why does Action extend ThreadSafe ?)
Date Wed, 15 Aug 2001 11:52:11 GMT
On Wednesday 15 August 2001 07:37, giacomo wrote:
> On Mon, 13 Aug 2001, Berin Loritsch wrote:
> > Mariano Kamp wrote:
> > > Hello Berin,
> > >
> > >   your explanations are quite helpful. Just one little question:
> > > >[..]
> > > >
> > > > 2) Generator: A generator performs XML generation from some external
> > > > source, whether it is a stream, an object, or database.  It must send
> > > > SAX events to the next component in a chain.  A Generator is always
> > > > the first component in a chain.  Due to the SAX implementation, it
> > > > cannot be ThreadSafe--but can be Pooled.
> > > >
> > > >[..]
> > > >
> > > > 4) Serializer: A serializer receives XML from a chain, and converts
> > > > it to an external stream.  A Serializer is the last element in a
> > > > stream. Again, it has the same constraints placed upon it as
> > > > Generator due to the same issues.
> > >
> > > I guess you are referring to the need to use instance variables? What I
> > > don't get is that there is no setup method in Serializer. I was already
> > > asking this once, but Giacomo just replied: "It is the way it is
> > > designed." Could you probably cast some light into the schadow?
>
> Serializers purpose are to serialize SAX events into streams. So there
> is no need for stuff passed in by the setup method in
> SitemapModelComponent (at least so far).
Ok, here is an example. I have a serializer which task it is to produce 
charts. It gets all the data as SAX-Events. Currently it also gets the width 
and the height of the images to be produced within the data. This is the only 
point where I need to "mess up" my data, with parameters about how the 
container of the images should be rendered. I would have appreciated to pass 
it to the serializer in the setup method, actually reading from the request 
parameters. 

Currently I do know put this height and width in my "report definitions", 
which are generated in the very beginning of my pipeline and are the base for 
all the dbQueries needed etc. So I push this information from step one to the 
last step, without any need to use it in the steps between. 

The last transformer does some xslt and I could also pass the width and 
height in there, but haven't done so, because my current approach is not too 
bad either. My point is. I don't absolutely need a setup() method in a 
Serializer, but I was wondering why there is none.

Thanks for enlightening me ;-)

Mariano 



> > I was refering to the SAX methods.  In regular use, it receives multiple
> > SAX events, so it does not have a single entry point, or a document
> > scoping method.
> >
> > >   So my real question is: If a serializer needs to have instance
> > > variables why shouldn't has it a setup() Method?
> >
> > The absence of the Setup method is due to the lack of runtime behavior
> > modification ability.  A serializer should function the same way every
> > time it is used, regardless of runtime parameters.  That is the main
> > reason it does not have a setup() method.
> >
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