How can I save one Entity containing another entity so they are linked together?

Question

I have a simple Order entity that contains OneToMany relation with a list of Dishes.

Order entity:

@Entity
@NoArgsConstructor
@AllArgsConstructor
@Getter
@Setter
@Table(name = "orders")
@ToString
public class Order {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;
    @Enumerated(EnumType.STRING)
    private Status status;
    private LocalDateTime creationDate;
    private LocalDateTime updateDate;
    private BigDecimal totalPrice;
    private String address;
    @ManyToOne(fetch = FetchType.LAZY)
    @ToString.Exclude
    private User user;

    @OnDelete(action = OnDeleteAction.CASCADE)
    @OneToMany(
            mappedBy = "order",
            cascade = CascadeType.ALL,
            orphanRemoval = true)
    @ToString.Exclude
    private List<Dish> dishes;

    public Order(long id, Status status, BigDecimal totalPrice, String address, List<Dish> dishes) {
        this.id = id;
        this.status = status;
        this.creationDate = LocalDateTime.now();
        this.updateDate = LocalDateTime.now();
        this.totalPrice = totalPrice;
        this.address = address;
        this.dishes = dishes;
    }
}

Dish entity:

@Entity
@NoArgsConstructor
@AllArgsConstructor
@Getter
@Setter
@ToString
public class Dish {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;
    private String name;
    private String description;
    private Category category;
    BigDecimal price;

    @ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @ToString.Exclude
    private Order order;

    public Dish(long id, String name, String description, Category category, BigDecimal price) {
        this.id = id;
        this.name = name;
        this.description = description;
        this.category = category;
        this.price = price;
    }

    public void setOrder(Order order) {
        this.order = order;
        order.addDish(this);
    }
}

Here I try to save Orders containg these dishes

Dish dish1 = new Dish(0, "Dish first", "Description of first Dish", Category.SNACKS, BigDecimal.valueOf(100));
Dish dish2 = new Dish(0, "Dish second", "Description of second Dish", Category.BURGERS, BigDecimal.valueOf(100));

List<Dish> dishes1 = Arrays.asList(dish1, dish2);
List<Dish> dishes2 = Arrays.asList(dish2);
Order order1 = new Order(0, Status.PENDING, BigDecimal.valueOf(150), "Address 1", dishes1);
Order order2 = new Order(0, Status.COMPLETED, BigDecimal.valueOf(150), "Address 2", dishes2);

Here is the problem, Dishes are persisted together with orders, but not associated with the Order Entity. Id is null

I know I didn't set order field when I created dishes, but how to do this If I need save both Order and Dishes at the same time.

Answer 1

You have the wrong model, what id do you expect to be in dish2? Relation between Order and Dish is NOT one-to-many, but many-to-many. Hibernate does not know what to enter in the column.