For your information, I've just pushed XMvn 2.5.0 to rawhide. It has improved Gradle integration, which allowed implementing %gradle_build in javapackages-tools.
The %gradle_build macro works just like %mvn_build, except it invokes Gradle instead of Maven. It also accepts the same arguments.
Once project is built with %gradle_build, it can be installed by invocation of %mvn_install. All other standard %mvn_* macros can also be used with %gradle_build.
I will try documenting this as time allows, but until it's done you can see spec files of other packages as example how to use this new macro.
http://pkgs.fedoraproject.org/cgit/gpars.git/tree/gpars.spec?id=1d2c7e0c17e6... http://pkgs.fedoraproject.org/cgit/spock.git/tree/spock.spec?id=a710e40d0d9b...
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