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From "Carsten Ziegeler" <cziege...@s-und-n.de>
Subject RE: [RT] Getting to the point of excalibur
Date Sat, 19 Jun 2004 09:10:27 GMT
Hamilton Verissimo de Oliveira 
> 
> -----Mensagem original-----
> De: Carsten Ziegeler [mailto:cziegeler@s-und-n.de] Enviada 
> em: sexta-feira, 18 de junho de 2004 05:22
> 
> > Yes, I think dynamic lookup is one of the major advantages 
> of Avalon. 
> > You can decide at runtime which components you need. This is not 
> > possible with setter/constructor injection.
> 
> Hmmm.. I think this is possible in a POJO world. Pico, for 
> instance, use component handlers and hints to (even) concrete 
> implementations. LSD can tell us more about that.
> 
Hmm, no, I don't think so - but perhaps I'm really wrong. Imagine
that you your implementation needs in some cases no service XY,
in some cases one instance of it and in some rare cases two instances.

If you are setter based, you only have one setXY() method, if you
use a constructor you could have two arguments for the services
there and then only use the amount of services you want, yes.
But that looks a little bit ugly to me :)

Of course the best examples come from Cocoon :) We build pipelines
on a per request base, based on the called uri, the environment etc.
Now, we have approx. 200 different pipeline components. Per request
only approx 5 are assembled to build the pipeline.
With a dynamic lookup mechanism you simply lookup the 5 components
you need per request and combine them. 
And I think these scenarios are perfect areas for Avalon.

Carsten


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