我是Spring Boot的新手，我看到Application-class使用CrudRepository接口。我看到从CrudRepository接口调用了.save（）方法，但是我不知道在哪里实现此方法。这会在春季后端发生吗？
这是应用程序类：
@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);
}
最佳答案
根据回答的位置Chan Chan：JpaRepository扩展了PagingAndSortingRepository，这又扩展了CrudRepository。
它们的主要功能是：
CrudRepository主要提供CRUD功能。
PagingAndSortingRepository提供分页和
排序记录。
JpaRepository提供了一些与JPA相关的方法，例如刷新
持久性上下文并批量删除记录。
这是我当前项目中实现CrudRepository，PagingAndSortingRepository和JpaRepository的示例。因此，当您只需要CRUD功能时，就可以实现它。当您需要分页与CRUD一起使用时。你去PagingAndSortingRepository。然后，当您需要更多功能时，JpaRepository适合您，
public interface CartRepository extends CrudRepository<ShoppingCart, Integer> {
@Query("select max(s.itemId) FROM ShoppingCart s")
public Integer findMaxItemId();
public List<ShoppingCart> findByCartId(String cartId);
public ShoppingCart findByItemId(int itemId);
}
public interface ProductRepository extends PagingAndSortingRepository<Product, Integer> {
@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 extends JpaRepository<Attribute, Integer> {
@Query("select new com.turing.ecommerce.DTO.AttributeDTO(a.attributeId, a.name)"
+ " from Attribute a ")
List<AttributeDTO> findAllAttributes();
}