Spring Data JPA

Spring Data JPA

Using Spring Data JPA can save you a lot of time when interacting with the database. Spring Data JPA implements the Repository Pattern. This design pattern was originally defined by Eric Evans and Martin Fowler, in their book Domain Driven Design. This is one of those time test computer science books, over a decade old, still remains relevant today.

You don’t need to use Spring Data JPA for this type of project. But using Spring Data JPA will make your life as a developer easier. A common alternative to Spring Data JPA would be to use the widely accepted DAO pattern, The DAO pattern is very similar to the Repository Pattern. The advantage of using Spring Data JPA is that you’ll be writing a lot less code. Spring Data JPA works a lot like Spring Integration Gateways, where you define an interface, and Spring provides the implementation at run time.

Spring Data JPA CRUD Repository

The Spring Data JPA CRUD Repository is my favorite feature of Spring Data JPA. Similar to coding with a Spring Integration Gateway, you can just define an interface. Spring Data JPA uses generics and reflection to generate the concrete implementation of the interface we define.

Defining a repository for our Product domain class is as simple as defining a interface and extending the CrudRepository interface. You need to declare two classes in the generics for this interface. They are used for the domain class the repository is supporting, and the type of the id declared of the domain class.

For our Product domain class we can define a Spring Data JPA repository as follows.

package guru.springframework.repositories;

import guru.springframework.domain.Product;
import org.springframework.data.repository.CrudRepository;

public interface ProductRepository extends CrudRepository<Product, Integer>{
}