replicator is null - replicator api

Am looking to activate the content items(as part of some node update activity)

For this i have built simple java stand alone application.

Am successfully able to:

1. Access the crx/de

2. traverse to the node

3. update

4. now i need to activate so am using:

replicator.replicate(session.getUserID(), ReplicationActionType.ACTIVATE, currentNode.getPath());

but am getting null pointer exception as replicator value is null. 

How can i get the replicator value with out making this application as aem service or anything?

Thanks for reading.