Passing fk in json via rest call as part of DerivedIdentities

Question

I got a Product entity that has an embedded key (id,manufacturer). I'm passing through REST call the product entity with fk of the manufacturer :

{
    "name":"Chocolate",
    "register_date":"19/03/2020",
    "manufacturer_id": 52,
    "rating":"Amazing"
}

When I try to save the entity in the controller I'm getting the following error

java.lang.IllegalArgumentException: Can not set com.dao.Manufacturer field com.dao.ProductId.manufacturer to java.lang.Long

Product :

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
@IdClass(ProductId.class)
@Entity
public class Product {

    @Id
    @SequenceGenerator(name = "product_id_seq", sequenceName = "product_id_seq", initialValue = 1)
    @GeneratedValue(strategy=GenerationType.SEQUENCE,generator = "product_id_seq")
    private Long id;

    @ManyToOne(fetch=FetchType.LAZY)
    @Id
    private Manufacturer manufacturer;
    
    private String name;

    @JsonFormat(pattern = "dd/MM/YYYY")
    private Date register_date;


    @Enumerated(EnumType.ORDINAL)
    private Rating rating;

    public enum Rating {
        Amazing,Good_Value_For_Money,Bad
    }

The Id class :

import lombok.AllArgsConstructor;
import lombok.NoArgsConstructor;

import java.io.Serializable;

@AllArgsConstructor
@NoArgsConstructor
public class ProductId implements Serializable {

    private Long id;
    private Manufacturer manufacturer;

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        ProductId pId1 = (ProductId) o;
        if (id != pId1.id) return false;
        return manufacturer.getId() == pId1.manufacturer.getId();
    }

    @Override
    public int hashCode() {
        return id.hashCode()+manufacturer.getId().hashCode();
    }
}

I also created a DTO object that will be passed through the api to the controller :

@Setter
@Getter
@AllArgsConstructor
@NoArgsConstructor

public class ProductCreationDTO {


    private String name;
    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "dd/mm/yyyy")
    private Date register_date;
    private Long manufacturer_id;
    private Product.Rating rating;

}

The manufacturer :

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
@Entity
public class Manufacturer {

    @Id
    @SequenceGenerator(name = "manufacturer_id_seq", sequenceName = "manufacturer_id_seq", initialValue = 1)
    @GeneratedValue(strategy=GenerationType.SEQUENCE,generator = "manufacturer_id_seq")
    private Long id;
    private String name;
    private String country;
    @OneToMany(mappedBy = "manufacturer",fetch = FetchType.LAZY)
    private List<Product> products;

In my controller I have the following 2 functions :

    RestController
    @RequestMapping("/api")
    public class ProductController {
    
        @Autowired
        ProductService productService;
    
        @Autowired
        ManufacturerService manufacturerService;
    
    
        @RequestMapping(value = "/product/", method = RequestMethod.POST)
        public HttpStatus insertProduct(@RequestBody ProductCreationDTO pcd) {
            Product p = mapProductCreationDTOtoProduct(pcd);
            if(p.getManufacturer() == null)
                return HttpStatus.BAD_REQUEST;
            return productService.addProduct(p) ? HttpStatus.CREATED : HttpStatus.BAD_REQUEST;
        }
    
        private Product mapProductCreationDTOtoProduct(ProductCreationDTO pcd)
        {
            Product p = new Product();
            p.setName(pcd.getName());
            p.setRating(pcd.getRating());
            p.setRegister_date(pcd.getRegister_date());
            Optional<Manufacturer> m = manufacturerService.getManufacturer(pcd.getManufacturer_id());
            if (m.isPresent())
                p.setManufacturer(m.get());
            return p;
        }

the add method under the productService : 

    @Transactional
    public boolean addProduct(Product p)
    {
        return productRepository.save(p)!=null;
    }

Update

I followed the following Stack Overflow post. I changed the ProductId to:

public class ProductId implements Serializable {

    private Long id;
    private Long manufacturer;
....

and in the Product class I added the following annotation above the Manufacturer :

@Id
@ManyToOne(fetch=FetchType.LAZY)
@MapsId("manufacturer")
private Manufacturer manufacturer;

and now I'm getting the following error:

org.hibernate.HibernateException: No part of a composite identifier may be null

Update 2

It looks like the id of the Product isn't populated and that's why it isn't created. I tried setting the id in the following function and the product was inserted successfully:

private Product mapProductCreationDTOtoProduct(ProductCreationDTO pcd)
{
    Product p = new Product();
    p.setName(pcd.getName());
    p.setRating(pcd.getRating());
    p.setRegister_date(pcd.getRegister_date());
    Optional<Manufacturer> m = manufacturerService.getManufacturer(pcd.getManufacturer());
    if (m.isPresent())
        p.setManufacturer(m.get());
    p.setId((long) 1);   <-------------------------------------------
    return p;
}

So the open question now is why the id isn't populated ?

score 1 · Answer 1 · answered Mar 20 '20 at 07:58

1

The obvious mistake is a @id annotation over the name property in the Product entity whereas it should be over the manufacturer property

answered Mar 20 '20 at 07:58

Yuriy Tsarkov

2,461
2
14
28

You are right, indeed the @id should have been above the manufacturer property. I changed that but I'm getting the same error. Not sure that it is related.. – JeyJ Mar 20 '20 at 09:49
does an `id` property in the `Manufacturer` entity annotate with `@Id`? – Yuriy Tsarkov Mar 20 '20 at 11:41
I fixed the original issue but another one appeared because of my solution, left an update on the main post – JeyJ Mar 21 '20 at 12:50
Left another update ,it seems like the id of the product that I create in the controller isnt initialized and thats why the exception is raised. – JeyJ Mar 21 '20 at 16:58

JeyJ · Accepted Answer · 2020-03-24T14:33:44.403

My original problem was :

java.lang.IllegalArgumentException: Can not set com.dao.Manufacturer field com.dao.ProductId.manufacturer to java.lang.Long

I solved it by following this post . The bottom line was that inside my IdClass, the type of the composite object should be his PK :

public class ProductId implements Serializable {

    private Long id; // matches name of @Id attribute
    private Long manufacturer; // name should match to @Id attribute and type of Manufacturer PK

Althought after solving it I faced a new :

org.hibernate.HibernateException: No part of a composite identifier may be null

might be a bug(or this bug) related to hibernate when using @Idclass.

Either way, the way to handle this problem and solve it is initiate the id column to a value :

public class Product {

    @Id
    @SequenceGenerator(name = "product_id_seq", sequenceName = "product_id_seq")
    @GeneratedValue(strategy= GenerationType.SEQUENCE,generator = "product_id_seq")
    private Long id=-1L;

This will bypass hibernate validation of the id and allow it to map the sequence value to it afterwards.

Passing fk in json via rest call as part of DerivedIdentities

Update

Update 2

2 Answers2