Ever heard of the JBoss AeroGear project? It's a pretty intriguing project that provides libraries to unify native, web, and hybrid mobile development. It has several features that make it appealing to Java enterprise developers. One of its most helpful libraries is the AeroGear Push Server, which is now available as an OpenShift Online Cartridge.
Jay Balunas has a solid tutorial on how to take advantage of this new release to help make your push notifications easy for multiple app types. AeroGear achieves the push functionality with a Java version of the Mozilla SimplePush server specification. It is available as a Netty-based server.