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From Matt Benson <gudnabr...@yahoo.com>
Subject Re: nested properties anyone?
Date Thu, 15 Aug 2002 17:59:19 GMT
Great--I had looked at <propertycopy> before and had
thought that might be its intent based on its
description, but the example provided didn't draw a
clear enough picture.  This example connected the
final dot for me.

Thanks,
Matt

--- Erik Hatcher <jakarta-ant@ehatchersolutions.com>
wrote:
>  From chapter 10 of Java Development with Ant [1]
> (gotta make my plugs 
> somehow!):
> 
> Copying properties
> In section 3.10.1 we demonstrate an obscure way to
> dereference property 
> values by using Ant's built-in capabilities. The
> ant-contrib [2] 
> <propertycopy> task makes property dereferencing
> much cleaner and easier 
> to understand. We have refactored the example we
> presented earlier to 
> use <propertycopy>:
> 
> <target name="propertycopy">
>    <property name="X" value="Y"/>
>    <property name="Y" value="Z"/>
>    <propertycopy name="A" from="${X}"/>
>    <echo message="A = ${A}"/>
> </target>
> 
> The value of ${X} is "Y". The from attribute of
> <propertycopy> refers to 
> an Ant property name, "Y" in this example. The value
> of the property Y 
> is "Z", so the output is "A = Z". This is a much
> nicer alternative than 
> using the refid tricks.
> 
> [1]
> http://www.amazon.com/exec/obidos/ASIN/1930110588
> [2] http://sourceforge.net/projects/ant-contrib/
> 
> 	Erik
> 
> 
> 
> Matt Benson wrote:
> > Agreed on nested properties expansion.
> > 
> > -Matt
> > 
> > --- bo@spamcop.net wrote:
> > 
> >>Problem:
> >>From the list of the predefined properties
> key=value
> >>select one based on the
> >>value of some other property and use it as a
> default
> >>
> >>Example:
> >>I have a list of servers (hosts.properties), where
> >>key is an actual hostname
> >>(obtained from hostname command) and value is a
> >>domain, e.g.
> >>host_one=host_one.somewhere.com
> >>host_two=host_two.some.place.else.com
> >>I want to determine on which machine I'm running
> the
> >>script and use a full
> >>domain name further in the script.
> >>
> >>Solution?
> >>1. <property file="hosts.properties"/>
> >>2. <exec outputproperty="hostname"
> >>executable="hostname"/>
> >>3. Now I have a ${hostname} and I want to assign
> its
> >>value to the property
> >>build.host that I use in my script. My first
> >>reaction was to do this:
> >><property name="build.host"
> refid="${${hostname}}"/>
> >>Well it didn't work because curleys are evaluated
> >>only once and I'm getting the
> >>value of build.host literaly as "${hostname}"
> >>Is there any other way? Any way? 
> >>And I think that it would be nice feature to
> >>reevaluate the nested brackets
> >>
> >>Bob Stone
> >>
> >>--
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> >>
> > 
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> 
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