Java Persistence APIs

These are the APIs and rules set by the framework. You can use them in any Java app. They work with any database.

• They define how database data maps to and from Java objects.
• They give APIs to act on the database.

ORM - Object-Relational Mapping

ORM makes database work simpler. It adds a layer that maps objects to database tables. You can use one language across the whole app.

Hibernate and Eclipselink are ORM libraries. Both follow the JPA rules.

Spring Data

Spring Data doesn't follow the JPA rules on its own. Instead, it wraps them. This saves you from writing boiler plate code for basic CRUD methods.

You make a repository by extending two interfaces. They're JpaRepository and JpaSpecificationExecutor. Spring then adds all the queries at compile time.

Repository Interfaces

A repository interface is one good example. It builds many methods for you.