具有 DTO 和 @manytoone 关系的 Spring Boot API Rest - 最佳实践

Question

I have the following configuration:

ProductPriceEntity

@Entity
@Table(name = "PRODUCTPRICE")
public class ProductPriceEntity {

    ...

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "SUPERMARKET_STORE_ID", nullable = false)
    private SupermarketStoreEntity store;

    ...
}

ProductPriceNewRequest

@Setter @Getter
public class ProductPriceNewRequest {

    ...

    private Long storeId;

    ...

}

ProductPriceControllerImpl

@PostMapping
@ResponseStatus(HttpStatus.CREATED)
public ResponseEntity<ProductPriceResponse> save(@PathVariable(value = "product_id", required = true) Long productId, @RequestBody @Valid ProductPriceNewRequest productPriceNewRequest) {
    ProductEntity productEntity = productService.findById(productId);

    ProductPriceEntity productPriceEntity = modelMapper.map(productPriceNewRequest, ProductPriceEntity.class);

    productPriceEntity.setProduct(productEntity);
    productPriceEntity = service.insert(productPriceEntity);

    URI location = ServletUriComponentsBuilder.fromCurrentRequest()
            .path("/{id}")
            .buildAndExpand(productPriceEntity.getId())
            .toUri();


    ProductPriceResponse productPriceResponse = modelMapper.map(productPriceEntity, ProductPriceResponse.class);

    return ResponseEntity.created(location).body(productPriceResponse);

}

ProductPriceResponse

@Getter @Setter
public class ProductPriceResponse {

    ...

    private String supermarket;
    private String store;

    ...
}

It's works but I can't to make return DTO. Supermarket and store are null on ProductPriceResponse.

Well, then I changed cascade of store attribute relationship.

@ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
@JoinColumn(name = "SUPERMARKET_STORE_ID", nullable = false)
private SupermarketStoreEntity store;

And I got this error:

"detached entity passed to persist: model.SupermarketStoreEntity; nested exception is org.hibernate.PersistentObjectException: detached entity passed to persist: model.SupermarketStoreEntity"

That makes sense. Modelmapper convert a long storeId to a SupermarketStoreEntity with just only id and detached ...

finally my question: What is best practice?

Should I get storeId and doesn't convert to a SupermarketStoreEntity detached and find SupermarketStoreEntity with your storeId on ProductPriceControllerImpl?

Or not. Should I to remove the cascade and after save ProductPriceEntity I will should fetch ProductPriceEntity saved? I suspect that store and supermarket still will get null because the cascade not there.

thank you all

Answer 1

Guess best practice is to introduce an @Service class, where you have a method with @Transactional annotation. The service is injected into the controller and all loading and saving of entities happens there. That should help with the detach-error.

I'm not a big fan of the cascade attribute and would favor doing this stuff in the code - but that's more an opinion.

Maybe you want to have a look at https://bootify.io - you can define your database with REST api there and get a sense of best practices for controllers and services.:)