Hello.

There was no problem when using Hibernate 6.1.7.Final version, but after upgrading to Hibernate 6.2.0.Final, the unique property of @JoinColumn always operates as true.

For example, two entities are:

• MemberShipCard Entity

  @Entity
  public class MembershipCard {
    @Id
    @Column(name = "card_number")
    private String number;
  ​
    @OneToOne
    @JoinColumn(name = "user_email")
    private Student owner;
  ​
    private LocalDateTime expiryDate;
  ​
    private boolean enabled;
  }

• Student Entity

  @Entity
  @EqualsAndHashCode(onlyExplicitlyIncluded = true)
  public class Student {
    @EqualsAndHashCode.Include @Id private String email;
    private String name;
  ​
    private LocalDateTime createDate;
  }

Table creation SQL for MemberShipCard entity in Hibernate 6.1.7.Final

    create table membership_card (
        card_number varchar(255) not null,
        enabled boolean not null,
        expiry_date timestamp(6),
        user_email varchar(255),
        primary key (card_number)
    )

Table creation SQL for MemberShipCard entity in Hibernate 6.1.7.Final

    create table membership_card (
        enabled boolean not null,
        expiry_date timestamp(6),
        card_number varchar(255) not null,
        user_email varchar(255) unique,  /* <-- Setting UNIUQE */
        primary key (card_number)
    )

Please inquire if there is any problem with the above operation.

• Example Project
  • https://github.com/mklinkj/QnA/tree/master/JPA/HibernateUpgradeJoinColumnTest
  • An example has been created in HSQLDB memory mode so you can check it right away