What apps folder for play framework container

Hi all
I am still struggling to run play-framework container!!!

Could anyone please help me answering;

  1. What ‘app’ folder should I ask my developer team to provide me that will be mounted during container creation from ingensi/play-framework?

docker run -d
-v /path/to/your/play/app:/app:rw \
-p 80:9000

what this app folder has to contain?

  1. Where database configuration file should possess? database is another postgres docker container.

  2. How do I verify that java is installed once image is created? Is it host OS level check or image or container level. I dont know.