How to disable creation link(entity in cross table) between entities (which have ManyToMany assotiation)

Hibernate ORM
1

Hello, dear collegues. Let me introduce my classes (in code) first to understand the problem

This is abstract class with authorUuid field. That field is about user identifier, who creates/updates/deletes entity. This field must be filled before execution query to database.

public abstract class BaseVersionedEntity extends BaseArchivableEntity implements Versioned {

    /**
     * Author UUID.
     */
    @ExportIgnore
    @Column(name = "author_uuid")
    private UUID authorUuid;

}

We have User, which may be in many groups. Group class doesn’t have @ManyToMany annotation to users

@Entity
@Table(name = AmUser.TABLE_NAME)
public class AmUser extends BaseVersionedEntity {

    public static final String TABLE_NAME = "am_user";

    @Id
    @SequenceGenerator(name = AM_SEQ_GENERATOR, sequenceName = AM_SEQUENCE_NAME, allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = AM_SEQ_GENERATOR)
    @Column(nullable = false, updatable = false)
    private Long id;

    @ManyToMany
    @JoinTable(name = "am_user_group",
            joinColumns = @JoinColumn(name = "am_user_id"),
            inverseJoinColumns = @JoinColumn(name = "am_group_id"))
    private Set<AmGroup> amGroups;

}

And we have entity for cross table

@Entity
@Table(name = AmUserGroup.TABLE_NAME)
public class AmUserGroup extends BaseVersionedEntity {

    public static final String TABLE_NAME = "am_user_group";

    @Id
    @SequenceGenerator(name = AM_SEQ_GENERATOR, sequenceName = AM_SEQUENCE_NAME, allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = AM_SEQ_GENERATOR)
    @Column(nullable = false, updatable = false)
    private Long id;

    @Column(name = "am_user_id", nullable = false, updatable = false)
    private Long amUserId;

    @Column(name = "am_group_id", nullable = false, updatable = false)
    private Long amGroupId;
}

The main problem is to fill ‘authorUuid’ field in ‘am_user_group’ table, because right now it fills using directional request to DB (Postgresql) by hibernate like "insert into am_user_group values(?,?).

Ideas, that works:

  1. Remove @ManyToMany link and send requests to database by ourselves. But it leads to fetching groups in additional requests, when we have users
  2. Add Sql Inresceptor, that add author id to sql prepared by hibernate

Also, I assume that you can turn off the automatic creation of an entity in cross table (am_user_group) and don’t remove @ManyToMany annotation. But how?
Maybe more relevant solution exists for this case. Could you please advise?

2

If you have columns in the am_user_group table other than the user and group id, which you do, then this is not a many-to-many assocation, but two one-to-many associations.

@Entity
@Table(name = AmUserGroup.TABLE_NAME)
public class AmUserGroup extends BaseVersionedEntity {

    public static final String TABLE_NAME = "am_user_group";

    @Id
    @SequenceGenerator(name = AM_SEQ_GENERATOR, sequenceName = AM_SEQUENCE_NAME, allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = AM_SEQ_GENERATOR)
    @Column(nullable = false, updatable = false)
    private Long id;

    @ManyToOne(fetch = LAZY)
    @JoinColumn(name = "am_user_id", nullable = false, updatable = false)
    private AmUser user;

    @ManyToOne(fetch = LAZY)
    @JoinColumn(name = "am_group_id", nullable = false, updatable = false)
    private AmGroup group;
}
@Entity
@Table(name = AmUser.TABLE_NAME)
public class AmUser extends BaseVersionedEntity {

    public static final String TABLE_NAME = "am_user";

    @Id
    @SequenceGenerator(name = AM_SEQ_GENERATOR, sequenceName = AM_SEQUENCE_NAME, allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = AM_SEQ_GENERATOR)
    @Column(nullable = false, updatable = false)
    private Long id;

    @OneToMany(mappedBy = "user")
    private Set<AmUserGroup> amGroups;

}