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From Nicola Ken Barozzi <nicola...@apache.org>
Subject Re: Ant 2 et al.
Date Tue, 09 Jul 2002 17:29:33 GMT

Erik Hatcher wrote:
> ----- Original Message -----
> From: "Nicola Ken Barozzi" <nicolaken@apache.org>
> 
>>IMHO it's better to use composition rather than inheritance, ie compose
>>common build parts in your builds, like Java use Java packages.
> 
> 
> I'm not entirely convinced of this yet, but I still need to ponder this
> some.
> 
> Example:
> I want to "inherit" a common web app project and add, say, XDoclet
> generation of web.xml.

import file="commonwebappproject.xml"
import file="xdocletgeneration.xml"

>>It's more a uses-a relationship rather than a is-a one.
>>
>>With imports you can modularize your builds.
> 
> 
> But I don't want to import all the pieces for every build.  I want to inject
> something into the dependency graph of an already pre-defined build.  How
> would that play out with imports?

Ah, "inject in the dependency graph" is a delicate point ;-)

If you want to not import everything, make an intermediate
buildfile that imports the single parts and have each of
your projects import that.

This means that each of your projects have access to the common build 
targets with a single import, and can create others via composition, ie 
by creating new targets and calling the original ones via antcall or 
depends.

You are not able to inject though a target in a defined place in the 
imported tree though.
It's specialization, what Maven does by giving hooks as pre and post 
targets to existing ones.

But this hides the dependency tree that is modifies.
If it's pre-made but hidden it's ok, but if it's modified *and* hidden, 
it hides what is happening and can bring to subtle errors.

-- 
Nicola Ken Barozzi                   nicolaken@apache.org
             - verba volant, scripta manent -
    (discussions get forgotten, just code remains)
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