Maven - activate child profile based on property

Question

Scenario:

1. Given
   1. Parent POM which defines a profile and a child (as module)
   2. Child project(s) that will be using the profile by referring to the parent POM.
2. The intent is to skip profile execution in the parent and execute it in the child only
3. Profile has activation section <activation><property><name>foo</name></property><activation>
4. Since parent does not define foo property - the profile is inactive and will not be executed for the parent build
5. Now, I'm defining <properties><foo>true</foo></properties> in the child with hope that the property will be picked up when child build is executed and profile will be activated. No such luck. Profile is never activated, which tells me that property is never set.
6. Just to note: mvn package -Dfoo=true activates profile in both parent and child

Am I trying to do the impossible or just doing it wrong?

P.S. Hmmm - even if I define property in the parent, the profile is not triggered. What gives?

Answer 1

The profile can only be activated by properties passed from the command line. This is because properties in the POM can only be processed once the POM has been parsed, at which point it is too late to resolve the profile activation.

You're in a bit of a catch-22 with this approach unless you are able to pass the property from the command line, specify profile activation in your settings.xml (generally not a great idea), or use the workaround in my previous answer to use the presence of a marker file.

One final alternative if you're on Maven 2.1.0+ is to deactivate the profile via the command line for the parent POM only, this is still obviously not ideal.

You can deactivate a profile with either the character '!' or '-' like this:

mvn install -P !profile-1,!profile-2

Answer 2

To directly answer my own question: in multi-module build all properties are set before build is run so it is impossible to activate/deactivate profile in one of the modules during the build based on setting the propety in the child POM. However if you are looking for way of doing it by using other means please read this comment