@Entity
@Table(name = "bar")
public class Bar {

    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Id
    private Long id;

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

@Entity
@Table(name = "foo")
public class Foo {

    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Id
    private Long id;

    @ManyToMany(mappedBy = "foo", cascade = CascadeType.ALL)
    private List<FooBar> fooBars;
}

@Entity
@Table(name = "foo_bar")
public class FooBar {

    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Id
    private Long id;
    @ManyToOne(fetch = FetchType.LAZY)
    private Bar bar;
    @ManyToOne(fetch = FetchType.LAZY)
    private Foo foo;
    private String note;

    @PrePersist
    void prePersist(){
        setNote("XXXXX");
    }
}