Chapter 4. Object-Relational Mapping

The largest part of an API that persists objects to a relational database ends up being the object-relational mapping (ORM) component. The topic of ORM usually includes everything from how the object state is mapped to the database columns to how to issue queries across the objects. We are focusing this chapter primarily on how to define and map entity state to the database, emphasizing the simple manner in which it can be done.

This chapter will introduce the basics of mapping fields to database columns and then go on to show how to map and automatically generate entity identifiers. We will go into some detail about different kinds of relationships and illustrate how they are mapped from the domain model to the data model.