In this video course, expert Java trainer and consultant Ken Kousen explores advanced database features that include switching databases, using multiple databases in a single Grails application, and how to invoke stored procedures by bypassing Hibernate. He also reveals how to map data to an existing database using Grails 3 custom ORM mapping tags. From there, he dives into a review of REST principles. He builds a RESTful web service using the rest-api profile, adds a RESTful controller, and looks at JSON views. Finally, he shows you how to conduct an integration test using a REST client.