Conditional property in Ant properties' file

ant, build.xml

Solution

Use the condition task:

<project name="demo" default="run">

    <condition property="my_property" value="${apache.root}/myapp" else="/var/www/myapp">
        <isset property="apache.root"/>
    </condition>

    <target name="run">
        <echo message="my_property=${my_property}"/>
    </target>

</project>

Problem

Is it possible to set a property value in Ant property files (as opposed to `build.xml`) in a conditional way? For example, if `apache.root` property is set - the `my_property` will be `${apache.root}/myapp`, `/var/www/myapp` otherwise. If not, what would be the common practice - reusable `build.xml` files?

Original source