Maven on Gentoo
Maven, Ant and Gradle are very wide spread Java build systems. Unfortunately it is not trivial to distribute source based ebuilds which require Maven. (see https://wiki.gentoo.org/wiki/Gentoo_Java_Packing_Policy#Maven)
Google Summer of Code
Improving the support of Maven was goal of several Google Summer of Code projects:
Packages waiting for Maven support
New packages for the tree which depend on Maven are organized by the tracker ticket bug #688542.