Spring Hibernate查询与非主键的一对一关系

Question

I am developing a web application on Spring with Hibernate.

This web application is basically an online commercial website with a number of products under a specific category.

This application supports multiple languages for a product and different sized pictures for a single product image for the sake of optimization based on different user devices. Therefore, users can choose in which language they'd like to see the description of products and will get different sized product image according to their device type such as mobile, iPad, desktop.

So, I have six tables at the moment as shown below.

The product table contains products as shown

The product_info table contains the same description in different languages for a product like English, Spanish, and Korean as shown in the picture below.

The product_image contains relative paths to the different sized images of the same picture for a product as shown in the picture below.

Let's say that a user requests a list of products under category_id = 1 (Furniture), support_language_id = 1 (English), and device_type_id = 1 (mobile). Then, I'd like to query something like the following, but in HQL.

Select * from product pr
left join product_info pf
on p.id = pf.product_id
left join product_image pi
on p.id = pi.product_id
where category_id = category_id of user choice
and support_language_id = support_language_id of user choice
and device_type_id = device_type_id of user device

When I execute this HQL query, I expect to get a list of product objects with each product object having only one product_info object and only one product_image object based on user-selected category_id, support_language_id, and device_type_id.

Following the example above, I will get a product object with id = 1 because there is only one object with category_id = 1. Then, the products object will have product_info object with id = 1 and product_image object with id = 1.

How can I implement this relationship into JPA with Hibernate?

I've tried this and that way but end up having errors like binding with non-primary key or others. So I am wondering if my database design has a structural problem in the first place.

Can you guys provide me a full working code example with all those JPA annotations like @JoinColumn, @OneToMany, @OneToOne and so on considered, please?

You can change, add, and remove columns or tables as long as I can have the desired result.

Answer 1

这里有一个不使用注解，只使用hql的解决方案，不知道能不能满足你。

select p from Product p,ProductInfo pf,ProductImage pi where p.id = pf.productId and p.id = pi.productId and...

Answer 2

Easy, assuming you don't have a 10 year old version of JPA then you can create two interfaces (repositories in this case) and name the methods as the JPA naming convention says. This means that if you have a class ProductInfo so defined:

@Data
@NoArgsConstructor
@AllArgsConstructor
public class ProductInfo {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "product_info_id")
    private long id;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "product_id")
    private Product product;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "language_id")
    private Language language;

    private String description;

}

This will be its respective Repository method you will need, and yes, you will need to pass the entire Product if you want to make it clean and simple.

 @Repository
 public interface ProductImageRepository extends JpaRepository<ProductImage, Long> {

    public Optional<ProductImage> findByProductAndDevice(Product product, Device device);

}

Same goes for the ProductImage

@Data
@NoArgsConstructor
@AllArgsConstructor
public class ProductImage {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "product_image_id")
    private long id;

    @ManyToOne
    @JoinColumn(name = "product_id")
    private Product product;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "device_id")
    private Device device;

    private String image;

}

Whose repository method will be

@Repository
public interface ProductImageRepository extends JpaRepository<ProductImage, Long> {

    public Optional<ProductImage> findByProductAndDevice(Product product, Device device);

}

Then you would want something to contain the product info

@Data
@AllArgsConstructor
@NoArgsConstructor
public class ProductToDisplay {

    private Product product;
    private String description;
    private String imageLocation;
}

And a service to then create that object based on the info you have

@Service
public class ProductToDisplayService {

    @Autowired
    private ProductInfoRepository productInfoRepository;
    @Autowired
    private ProductImageRepository productImageRepository;

    @Autowired
    private ProductRepository productRepository;
    @Autowired
    private DeviceRepository deviceRepository;
    @Autowired
    private LanguageRepository languageRepository;

    public ProductToDisplay getProduct(long productID, long languageID, long deviceID) throws Exception {
        Product product =
                productRepository.findById(productID).orElseThrow(()-> new Exception(
                        "There is no such product"));

        return new ProductToDisplay(product,
                productInfoRepository.findByProductAndLanguage(product,
                        languageRepository.findById(languageID).orElseThrow(()-> new Exception(
                                "There is no such product"))).orElseThrow(()-> new Exception(
                        "There is no such product info")).getDescription(),
                productImageRepository.findByProductAndDevice(product,
                        deviceRepository.findById(deviceID).orElseThrow(()-> new Exception(
                                "There is no such product"))).orElseThrow(()-> new Exception(
                        "There is no such product Image")).getImage());
    }
}

Which might seem a little bit confusing here and I'm sorry about that but this is a little bit more clear

public ProductToDisplay getProductClear(long productID, long languageID,
                                     long deviceID) throws Exception {
    Product product =
            productRepository.findById(productID).orElseThrow(()-> new Exception(
                    "There is no such product"));

    Language language = languageRepository.findById(languageID).orElseThrow(()-> new Exception(
            "There is no such language"));
    ProductInfo prodInfo = productInfoRepository.findByProductAndLanguage(product, language)
            .orElseThrow(()-> new Exception(
            "There is no such product info"));

    Device device =  deviceRepository.findById(deviceID).orElseThrow(()-> new Exception(
            "There is no such image"));
    ProductImage prodImg = productImageRepository.findByProductAndDevice(product, device)
            .orElseThrow(()-> new Exception(
            "There is no such product Image"));

    return new ProductToDisplay(product,
            prodInfo.getDescription(), prodImg.getImage());
}