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From "Knut Wannheden" <>
Subject Re: PropertyHelper (was: Re: beating the dead Ant 1.6 horse)
Date Thu, 14 Aug 2003 11:14:35 GMT
Sounds great!

In anticipation of this feature I have used a few namespaced properties for
my custom tasks.  And since Ant 1.5 doesn't have any value for these, I've
just made the tasks resolve them explicitly.

This raises a question: Are properties whose values are resolved by custom
PropertyHelpers always converted to Strings?  I see that the return type of
PropertyHelper#getPropertyHook(String, String, boolean) has Object as the
return type.  But if that's always converted to a String then my custom
PropertyHelper will need to make sure that this is done correctly, i.e. that
the Object yields a meaningful String representation.

But for tasks which have a setXXX(Object) method it would maybe make sense
to preserve the property value as an Object instance, if that's what's
actually in the buildfile.  E.g.

    <foo xxx="${my:bar}"/>

would not convert the ${my:bar} property to a String.



"Nicola Ken Barozzi" <> wrote in message
> Dominique Devienne wrote, On 12/08/2003 15.37:
> > I'm also interested PropertyHelper, and in particular Costin's
> > experimental XPath based one. I'd like to be able to define
> > functions (defined as part of an AntLib) to operate directly on
> > property values, kind of like XPath functions, and it sounds like
> > property helper is the way to get this!?!? --DD
> Yes. PropertyHelper is a property interceptor, and it simply rocks.
> In essence, you register a helper with Ant. Then, at each request for a
> property, each registered helper is asked for the property value in
> turn; the first one that has it, returns it.
> A typical one is the xpath one, as you say, that resolves the request as
> an xpath in the Ant Project, if the property starts with "xpath:".
> Centipede has been using it for a long time, basically to read an xml
> file as a property in a more powerful way than simply using xmlproperty.
> Now we are doing our own helper that reads the Gump descriptor, the
> Maven one, etc and makes them all accessible as a single virtual
> descriptor. In this way Ant users can have any descriptor they want and
> use that to gather properties and infos for the project.
> Just an example of the usage of PropertyHelper.
> -- 
> Nicola Ken Barozzi         
>              - verba volant, scripta manent -
>     (discussions get forgotten, just code remains)
> ---------------------------------------------------------------------

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