There is one example, which is rather more complicated than might be first expected.
Typesafe provide an activator with source. This implementation directly references an internal Spark component SparkEnv, whose documentation indicates that external usage is discouraged and it may be made private in a future release. The placement of SparkEnv within the Java API is a further discouragement.
Spark contains an official zeromqReceiver that uses ActorHelper, without all the issues mentioned above.
DataStax provide a Cassandra Connector Demo