Hibernate

Bi-Directional Many to Many using user managed join table object

June 11, 2022 by aAshish

@Entity

@Table(name = "FOO")
public class Foo {
  private UUID fooId;

  @OneToMany(mappedBy = "bar")
  private List<FooBar> bars;
}

@Entity
@Table(name = "BAR")
public class Bar {
  private UUID barId;

  @OneToMany(mappedBy = "foo")
  private List<FooBar> foos;
}

@Entity
@Table(name = "FOO_BAR")
public class FooBar {
  private UUID fooBarId;

  @ManyToOne
  @JoinColumn(name = "fooId")
  private Foo foo;

  @ManyToOne
  @JoinColumn(name = "barId")
  private Bar bar;
  // You can store other objects/fields on this table here.
}

Specifies a two-way relationship between many Foo objects to many Bar objects using an intermediate join table that the user manages.

The Foo objects are stored as rows in a table called FOO. The Bar objects are stored as rows in a table called BAR. The relationships between Foo and Bar objects are stored in a table called FOO_BAR. There is a FooBar object as part of the application. 

Commonly used when you want to store extra information on the join object such as the date the relationship was created.