Hibernate how to add and display in essence an additional column in the binding ManyToMany table?

Question

Java

Good day, please tell me how to solve this problem correctly:
I have 2 entities

• Products
  
  • id
    
  • Name
    
  • cost
    
  • Category
    
  
  
• Transactions
  
  • id
    
  • List (Product)
    
  
  

The relationship between them is Many to many, that is, the transaction_product table has been created with the following fields:

• transaction_id
  
• product_id
  

respectively.

entity classes look something like this:

product

@Entity
@Table(name = "products")
public class Product {
  
  @Id
  @Column(name = "id")
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private int id;
  
  @Column(name = "name")
  private String name;
  
  @ManyToOne(cascade = {CascadeType.DETACH,CascadeType.MERGE,CascadeType.REFRESH}, fetch = FetchType.LAZY)
  @JoinColumn(name = "category")
  private Category category;
  
  @Column(name = "cost")
  private Double cost;
//constructor getter setter
}

transaction

@Entity
@Table(name = "transactions")
public class Transaction {

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



    @ManyToMany(cascade = {CascadeType.MERGE, CascadeType.REFRESH, CascadeType.DETACH},
            fetch = FetchType.LAZY)
    @JoinTable(
            name = "transactions_products",
            joinColumns = @JoinColumn(name = "product_id"),
            inverseJoinColumns = @JoinColumn(name = "transaction_id")
    )
    private List<Product> products;
//constructor getter setter
}

Here I needed to add another "quantity" column that displays the number of specific products in a transaction. It is most logical to add transaction_product to the table - but here is a stupor, but how to display it in java?
Probably something like this?
private List<Map<Product, Integer>> products;
but how to connect it with hibernate?

or shouldn't it be done?

Answer 1

Good afternoon.
I recently answered a similar question:
https://qna.habr.com/q/1114434