使用 springboot 创建端点的问题

Question

My task is to create endpoint, the logic is:
User provides input --> nip (one of the variables in Contractor.class ) on the basis of that nip , I must return JSON, which will contain information about the product that is assigned to the contractor with the provided nip . Example JSON should look like: { "name": "product_name", "quantity": "0", "address": "storage_address"}

I spent lots of time on this problem, but still don't know what logic to implement. It's over my newbie head;

Product.class :

public class Product extends AbstractEntity {


    @Id
    @GeneratedValue
    private Long id;
    private String name;
    private long quantity;


    @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true, mappedBy = "product", fetch = FetchType.EAGER)
    private List<Assignment> assignments;


    @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true, mappedBy = "product")
    private List<Place> places;
}

Contractor.class :

public class Contractor extends AbstractEntity {

    @Id
    @GeneratedValue
    private Long id;
    private String contractorName;
    private int nip;

    @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true, mappedBy = "contractor")
    private List<Assignment> assignments;
}

Assignment.class :

public class Assignment extends AbstractEntity {

    @Id
    @GeneratedValue
    private Long id;


    @JsonIgnore
    @ManyToOne
    @JoinColumn(name = "id_product", referencedColumnName = "id", nullable = false)
    private Product product;

    @JsonIgnore
    @ManyToOne
    @JoinColumn(name = "id_contractor", referencedColumnName = "id", nullable = false)
    private Contractor contractor;

}

Storage.class :

public class Storage extends AbstractEntity {

    @Id
    @GeneratedValue
    private Long id;
    private String address;

    @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true, mappedBy = "storage")
    private List<Place> places;
}

Place.class :

public class Place extends AbstractEntity {

    @Id
    @GeneratedValue
    private Long id;
    private Long shelfNumber;

    @JsonIgnore
    @ManyToOne
    @JoinColumn(name = "id_product", referencedColumnName = "id")
    private Product product;


    @JsonIgnore
    @ManyToOne
    @JoinColumn(name = "id_storage", referencedColumnName = "id", nullable = false)
    private Storage storage;

}

image of ERD Diagram

Answer 1

I do not know what logic do you need precisely. Also I am not sure if that code will fit to rest of your app. But maybe it will help.

The interface which will be returned by repository and by the rest controller:

public interface GetProductResponse {
    public String getName();
    public int getQuantity();
    public String getAddress();
}

The repository where you can write your query:

public interface ProductRepository extends CrudRepository<Product, Long>  {
    @Query(nativeQuery = true, 
    value = (
"SELECT product.name AS name, product.quantity AS quantity, storage.address " + 
//be sure to name the result columns the variables in GetProductResponse (without the 'get')
"FROM contractor INNER JOIN assignment ON contractor.id = assignment.id_contractor " +
" INNER JOIN product ON product.id = assignment.id " +
" INNER JOIN place ON product.id = place.id_product " +
" INNER JOIN storage ON storage.id = place.id_storage " +
"WHERE contractor.nip = :nip_ "
    )
    public List<GetProductResponse> getProducts(@Param("nip_")String nip)
}

The rest controller:

@RestController
public class Controller {
    @RequestMapping(value = "/getProductsByNip", method = { RequestMethod.POST})
    public List<GetProductResponsee> getProductsByNip(@RequestBody String nip) {
        return productRepository.getProducts(nip);
    }
}

The output will look like:

[
{"name": "product_name1", "quantity": "0", "address": "storage_address1"},
{"name": "product_name2", "quantity": "2", "address": "storage_address2"}
]