Just Spring Data Access

Chapter 4. Spring JPA

When comes to ORM frameworks, plenty of frameworks exist. We have already seen Hibernate in our last chapter. Frameworks may have a free hand when it comes to implementation if no standard is around. A standard or a specification helps the end user in swapping the frameworks without much hassle should the need arise. Java folks realised the need of a persistence standard that would help the user community. The standard is called a Java Persistence API (JPA)—an API that helps to standardize the Java Persistence world.

In this chapter, we will look at the Java Persistence API at a high level and at Spring’s support to use the API with few providers, especially with the Hibernate provider. As expected, there will be a few players who implement the specification and bring the standard to life. We see discuss one such provider—Hibernate itself—in this chapter.

Two-Minute JPA

The JPA defines an EntityManager interface, which is basically the heart of the API. It is similar to Hibernate’s Session, forming the core of the application to perform database operations.

As you create Session from a SessionFactory, it’s not hard to understand that you use EntityManagerFactory to create an instance of EntityManager. However, because JPA is a standard applicable to Enterprise and Standalone applications, there are a couple of modes for obtaining or creating the EntityManagerFactory itself—one that will be created in a managed environment such as Application Servers or Web containers ...