Spring Data Repositories

According to Martin Fowler, a repository mediates between the domain and data mapping layers using a collection-like interface for accessing domain objects.

In Spring Data JPA, repositories extend one of the Repository generic interfaces, including CrudRepository, ListCrudRepository, and JpaRepository.

To act on the data in a table, simply extend the interface of your choice by providing the entity type corresponding to the table and the type of its primary key.

1import org.springframework.data.jpa.repository.JpaRepository;
2
3public interface ProductRepository extends JpaRepository<Product, Long> {
4}

To define specific queries, we will mainly rely on the strategy described here.

1import org.springframework.data.jpa.repository.JpaRepository;
2
3import java.util.List;
4
5public interface OrderRepository extends JpaRepository<Order, Long> {
6
7    List<Order> findByOrderLinesQuantityGreaterThanEqual(int quantity);
8
9}