[FIXED] Spring Boot + Hibernate: Custom fields on auto-generated pivot tables

Issue

In a Model I have:

public class House {
    ....
    ....
    @OneToMany
    @Nullable
    private List<Person> people;

When running the Spring Boot application, I will see thee tables created. One for the House model, one for the Person and another one, automatically generated pivot table to keep relationship information House and Person.

My question is: what If I wanted to add a created_at field onto the rows of the pivot table, so that for each association of House to Person I'd be able to tell when it was created.

I could not find a way to do that. What am I missing?

Solution

You should create an additional entity for the join table (House_Person). Inside of the new entity you declare the additional fields you need like created_at. Lastly you only need to link your both entitys to the new entity with @ManyToOne:

House_Person Entity:

@Entity
@Table(name = "HOUSE_PERSON")
public class HousePerson {
  ...

  private Person person;
  private House house;
 
  // additional fields
  private Date created_at;
  
  ...

  private Person person;
  @ManyToOne(cascade = CascadeType.ALL)
  @JoinColumn(name = "PERSON_ID")
  public Person getPerson() {
    return person;
  }

  private House house;
  @ManyToOne(cascade = CascadeType.ALL)
  @JoinColumn(name = "HOUSE_ID")
  public House getHouse() {
    return house;
  }
}

Have a look at this example here I hope that describes it well: codejava.net/hibernate-many-to-many-association-with-extra-columns-in-join-table-example

Answered By - anme98
Answer Checked By - Katrina (JavaFixing Volunteer)