[Q] Best method to create a rest api with an already existing database. (no replies)

I am trying to develop a RESTful web service with Java and most of the examples are creating the database from scratch. Javascript let us access the database and create it but the people that we are creating this project for asked us to switch to Java. We want to access and use the existing database we created and create the restful service.

We have tried using spring, gradle, and jersey. Most of the guides are for making a connection and creating the database but not using an existing one already.