我是Spring Boot的新手，我发现Application-class使用了CrudRepository接口。我看到来自CrudRepository接口的.save（）-method被调用，但我不明白这个方法的实现位置。这是否发生在Spring的后端某处？
这是Application-class：
@SpringBootApplication
public class Application {
private static final Logger log = LoggerFactory.getLogger(Application.class);
public static void main(String[] args) {
SpringApplication.run(Application.class);
}
@Bean
public CommandLineRunner demo(CustomerRepository repository) {
return (args) -> {
// save a couple of customers
repository.save(new Customer("Jack", "Bauer"));
repository.save(new Customer("Chloe", "O'Brian"));
repository.save(new Customer("Kim", "Bauer"));
repository.save(new Customer("David", "Palmer"));
repository.save(new Customer("Michelle", "Dessler"));
// fetch all customers
log.info("Customers found with findAll():");
log.info("-------------------------------");
for (Customer customer : repository.findAll()) {
log.info(customer.toString());
}
log.info("");
// fetch an individual customer by ID
repository.findById(1L)
.ifPresent(customer -> {
log.info("Customer found with findById(1L):");
log.info("--------------------------------");
log.info(customer.toString());
log.info("");
});
// fetch customers by last name
log.info("Customer found with findByLastName('Bauer'):");
log.info("--------------------------------------------");
repository.findByLastName("Bauer").forEach(bauer -> {
log.info(bauer.toString());
});
// for (Customer bauer : repository.findByLastName("Bauer")) {
// log.info(bauer.toString());
// }
log.info("");
};
}
}
CustomerRepository扩展了CrudRepository：
public interface CustomerRepository extends CrudRepository<Customer, Long> {
List<Customer> findByLastName(String lastName);
}
根据陈灿的回答：
JpaRepository扩展了PagingAndSortingRepository，后者又扩展了CrudRepository。
他们的主要职能是：
CrudRepository mainly provides CRUD functions.
PagingAndSortingRepository provides methods to do pagination and sorting records.
JpaRepository provides some JPA-related methods such as flushing the persistence context and deleting records in a batch.
以下是我当前项目中的一个示例，其中我实现了CrudRepository，PagingAndSortingRepository和JpaRepository。因此，当您只需要CRUD函数时，就可以实现它。当你需要与CRUD一起分页时。你去PagingAndSortingRepository。然后，当您需要更多功能时，JpaRepository会适合您，
public interface CartRepository扩展了CrudRepository {
@Query("select max(s.itemId) FROM ShoppingCart s")
public Integer findMaxItemId();
public List<ShoppingCart> findByCartId(String cartId);
public ShoppingCart findByItemId(int itemId);
}
公共接口ProductRepository扩展PagingAndSortingRepository {
@Query(value = "select p from Product p where p.description = SUBSTRING(p.description, 1,:description_length)")
List<Product> getAll(@Param("description_length")Integer description_length, Pageable pageable);
@RepositoryRestResource
public interface AttributesRepository扩展JpaRepository {
/**
* Retrieves all attributes.
*
*
* @return the attribute objects
*/
@Query("select new com.turing.ecommerce.DTO.AttributeDTO(a.attributeId, a.name)"
+ " from Attribute a ")
List<AttributeDTO> findAllAttributes();
}
}