This chapter covers how to use Java Persistent API (JPA) with Spring Boot and how to define a database by using entity classes. In the first phase, we will be using the H2 in-memory database for development and demonstration purposes. H2 is an in-memory SQL database that is really good for fast development or demonstration purposes. In the second phase, we will move from H2 to use MariaDB. This chapter also describes the creation of CRUD repositories and a one-to-many connection between database tables.

In this chapter, we will cover the following topics:

• Basics of Object-Relational Mapping (ORM), JPA, and Hibernate
• Creating the entity classes
• Creating CRUD repositories 
• Relationships between tables 
• Setting up the MariaDB database