Many-to-Many Relationship in Hibernate with Extra Column

Question

I have database stucture like this. It is for user access control in my application.

 UserGroup
 ==========
 id (PK)
 code
 name


 HakAkses
 ==========
 id(PK)
 UserGroup_id (FK)
 Akses_id (FK) 
 action_create
 action_read
 action_update
 action_delete


 Akses
 ==========
 id(PK)
 code

And I make the hibernate annotation like this

@Entity
@Table(name = "[Master].[UserGroup]")
public class UserGroup implements Serializable{
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column(unique = true, length = 10)
    private String kode;
    private String nama;

    @OneToMany(mappedBy = "userGroup")
    private Set<HakAkses> hakAksesSet;
}

@Entity
@Table(name = "[master].[HakAkses]")
public class HakAkses implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @ManyToOne
    @JoinColumn(name = "UserGroup_id", nullable = false)
    private UserGroup userGroup;

    @ManyToOne
    @JoinColumn(name = "Akses_id", nullable = false)
    private Akses akses;

    @Column(name = "action_create")
    private boolean canCreate;
    @Column(name = "action_read")
    private boolean canRead;
    @Column(name = "action_update")
    private boolean canUpdate;
    @Column(name = "action_delete")
    private boolean canDelete;
}

@Entity
@Table(name = "[master].[Akses]")
public class Akses implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column(unique = true)
    private String kode;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "akses")
    private List<HakAkses> hakAksesSet;
}

And then I tried in my tester with this code

UserGroup userGroup = new UserGroup(kode, nama);
userGroup.setHakAksesSet(new HashSet<HakAkses>(hakAksesList));
this.controller.save(userGroup);

But when I run the tester, the data was saved in database only UserGroup data. Is there any problem with my hibernate annotation?

Thank you

Answer 1

This is because the cascade annotation is missing on the parent entity. See if this helps

@Table(name = "[Master].[UserGroup]")
public class UserGroup implements Serializable{
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column(unique = true, length = 10)
    private String kode;
    private String nama;

    @OneToMany(mappedBy = "userGroup", cascade = CascadeType.ALL)
    private Set<HakAkses> hakAksesSet;
}

Answer 2

Your mapping uses mappedBy , which among other settings, does inject the inverse="true" setting to the one-to-many end. Read more about this here:

• inverse = “true” example and explanation by mkyong

In a nutshell, that means, that Hibernate is instructed: the other (many-to-one) end will care about persisting. Also, try to go through this example in documentation

23.2. Bidirectional one-to-many

This example shows inverse in action, some essential cites:

... Now that the Child entity is managing the state of the link, we tell the collection not to update the link. We use the inverse attribute to do this:

<set name="children" inverse="true">
    <key column="parent_id"/>
    <one-to-many class="Child"/>
</set>

The following code would be used to add a new Child:

Parent p = (Parent) session.load(Parent.class, pid);
Child c = new Child();
c.setParent(p);
p.getChildren().add(c);
session.save(c);
session.flush();

Only one SQL INSERT would now be issued.

So what we see there?

• inverse setting is what we need. It improves performance (and we have it due to mappedBy)
• but it is not enough to set the relation on the one-to-many side. We MUST set a parent to each child .

So, you should extend this:

UserGroup userGroup = new UserGroup(kode, nama);
userGroup.setHakAksesSet(new HashSet<HakAkses>(hakAksesList));
// this is not enough - we also MUST 
// FOR each HakAkses in the  list 
// SET a Parent, i.e hakAksses.setUserGroup(userGroup)

Finally, there (almost) always should be cascading turned on. One should not care about that manually:

@OneToMany(mappedBy = "userGroup", cascade = CascadeType.ALL)