How to make sure that engine is started once

Flowable Engine
1

I am using the example given at http://www.flowable.org/docs/userguide/index.html#_creating_a_process_engine, but with persistent database. From my understanding, I should have only one instance of Flowable engine, how would I make sure that only one instance exists at any given time?

2

Have the process engine as a spring bean (there will be only one instance) or keep it somewhere globally accessible (static is possible, the processEngine is threadsafe).