I might have a design problem, so first of all I would like to explain the design.

Imagine I have a conference with 3 kind of speakers. So I have the entity Conference and the entity Speaker.

The entity Speaker has 3 attributes: speaker1, speaker2 and speaker3 of the entity Speaker. The way I've mapped this is the following.

@Entity
@Table(name = "SPEAKERS")
public class Speaker
{
@Id
@Column(name = "ID_SPEAKER")
private Long idSpeaker;

//other fields like name, etc...

// getter and setter
}


@Entity
@Table(name = "CONFERENCES")
public class Speaker
{
@Id
@Column(name = "ID_CONFERENCE")
private Long idConference;

@ManyToOne
@JoinColumn(name = "ID_SPEAKER")
private Speaker speaker1

@ManyToOne
@JoinColumn(name = "ID_SPEAKER")
private Speaker speaker2

@ManyToOne
@JoinColumn(name = "ID_SPEAKER")
private Speaker speaker3

// getters and setters
}

If I do this, I get the org.hibernate.MappingException: Repeated column in mapping for entity..........

What would be the proper design for such issue? Inheritance?

Thank you very much.

Hello Bertyno, you have two options:

If you only need to have 3 speakers and only 3 you could mappe it as



or if you gonna have more than 3 speaker you should go to a OneToMany Approach



and the Speaker:



Regards,

I am a newbie but I believe what you are seeing is a result of Hibernate defining a new 'ID_SPEAKER' column in order to map the @ManyToOne associations. To avoid this you need to change your @JoinColumn spec as follows:

@JoinColumn(name="ID_SPEAKER", insertable=false, updatable=false)

Cheers.

mocando, Hibernate it's not just defining one column with the name of ID_SPEAKER but 3. Even if you use insertable=false and updatable=false you will have one column that you could not write to or update to; if that so, then, when hibernate it's retrieving the data how it will know which property to fill, with only one column for 3 properties. I think that what's bertyno it's trying to achieve it's a little more complex than that.

regards,