Hello,

because of the immutability of properties you have to redesign your scripts.
The first time you set a property is it. You are usually not able t change it 
later.
This is very important, because this is the only way to set properties from 
outside.

Why does your command line call then use "-D-DoutFileName=START", when you 
don’t want it?

Never do this, when you want to change the prop in your build.
If "START" is your default, then set it in the called target / Ant file, in 
your case "called.xml"

Its very important to understand why immutability is a feature and not a bug... 
(-;

Juergen





-----Ursprüngliche Nachricht-----
Von: Al Le [mailto:al...@gmx.de] 
Gesendet: Donnerstag, 31. Juli 2014 11:10
An: user@ant.apache.org
Betreff: How to override a property that was set in the command line via "-D..."

user@ant.apache.org

How to override a property that was set in the command line via "-D..."

Hello.

Could someone please help me with the following situation?

I have some ant scripts that are used in two ways:

1. Standalone build, i.e. the script is executed directly from the command line 
2. As a part of a larger build -- then the script is called via 'ant' from 
another
    script (here we have a main and a called scripts).

Each script uses a property 'outFileName' that specifies where to write some 
output to.
Both the main and the called script use this property. The script gets the 
value of the property passed from the caller.

The root script (i.e. the one called from the command line) gets passed the 
value of 'outFileName' via the "-DoutFileName=..." option.

When the main script calls a called script, it may specify another value for 
the property 'outFileName' (using the nested 'property' element). The called 
script should notice no difference how it was called (i.e. whether it is called 
from the command line or as a called script from another script).

Now the propblem: It turns out that the properties specified via "-D=..." are 
set as *user* properties. Hence it's not possible to redefine them via the 
nested elements. Ant not even using a script task with a call 
'project.setProperty()'.

How would you solve this situation? I would not like introduce properties with 
a different name, since my goal is to have scripts that can be 'customized' by 
specifying a property with a well known name ('outFileName') -- be it on the 
command line or trough a nested element of an ant task. Thik of it as of script 
interface.

The only possible solution I can think of is to specify a custom property 
helper, but that's too much IMO and makes scripts not 'portable'.

Here's an example that I hope would explain the problem (I use ant 1.8.4 but I 
think the same problem would also occur with ant 1.9.x):


-- Main build file 'main.xml' --

<project name="Main" default="run">
        
    <target name="run">
        <echo>Main: outFileName: ${outFileName}</echo>
        
        <ant antfile="called.xml" target="run">
                <property name="outFileName" value="OTHER VALUE"/>
        </ant>
    </target>
        
</project>


-- Called build file 'called.xml' --
<project name="Called" default="run">
        
    <target name="run">
        <echo>Called: outFileName: ${outFileName}</echo>
    </target>

</project>


-- Command line --
ant -f main.xml -DoutFileName=START


-- Actual output --
run:
     [echo] Main: outFileName: START
run:
     [echo] Called: outFileName: START


-- Expected (desired) output --
run:
     [echo] Main: outFileName: START
run:
     [echo] Called: outFileName: OTHER VALUE


Any help will be much appreciated.

Al

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