@OneToOne in @Embedded element

risc · **Posted:** Tue Sep 20, 2005 10:22 am

I am trying to map two embeddable objects with a reference to another object (see code) using an existing database:

Code:

@Entity(access=AccessType.FIELD)
public class Article {
   @Id
   String artnr;
   //...more defs
}

@Embeddable(access = AccessType.FIELD)
public class Unit {
   @OneToOne
   @JoinColumn(name="unit_artnr",referencedColumnName="artnr")
   Article article;
   Integer amount;
   //... more defs
}

@Entity(access = AccessType.FIELD)
public class Order {
   @Embedded
   @AttributeOverrides({
         @AttributeOverride(name="article",column=@Column(name="bunit_artnr")),
      @AttributeOverride(name="amount",column=@Column(name="bunit_amount"))
   })
   Unit bunit;
   @Embedded
   @AttributeOverrides({   
         @AttributeOverride(name="article",column=@Column(name="lunit_artnr")),
      @AttributeOverride(name="amount",column=@Column(name="lunit_amount"))
   })
   Unit lunit;
}

The code should finally boil down to this table:

Code:

Table Order
   -- ...
   bunit_artnr varchar(10),
   bunit_amount integer,
   lunit_artnr varchar(10),
   lunit_amount integer,
   -- ...

Instead of this I get the following error from hibernate:

Code:

   INFO: processing foreign key constraints
org.hibernate.MappingException: Repeated column in mapping for entity: com.softworks.pronto.model.Order column: unit_artnr (should be mapped with insert="false" update="false")
   at org.hibernate.mapping.PersistentClass.checkColumnDuplication(PersistentClass.java:550)

As far as I can tell the field name is not correctly substituted when the element is a @OneToOne.
I can remove lunit, leaving only the single reference to bunit, in which case the generated sql is incorrect unless I modify the @JoinColumn in Unit to

Code:

@JoinColumn(name="bunit_artnr")

but this is counterproductive and not what I intend to do.

Any ideas on how to fix this?

Version Info: annotation-3.1b5

emmanuel · **Posted:** Wed Sep 21, 2005 5:38 am

http://www.hibernate.org/329.html#A3

risc · **Posted:** Thu Sep 22, 2005 2:25 am

Is there a chance that these annotations will be implemented in the near future? Embedded objects are nearly useless without them and I have to add a lot of complexity to my code when working around it.

Another "nice-to-have" would be @Version in an @Embeddable.

Thanks for your help.

emmanuel · **Posted:** Thu Sep 22, 2005 6:31 am

I guess I need to work on that sooner or later

But what's the use case for @Version in an @Embeddable?
I not even sure H3 core support that, doesn't really make sense to me.

risc · **Posted:** Thu Sep 22, 2005 8:50 am

Make it sooner, it would help me a lot. Thanks in advance.

concerning @Version

Code:

@Embeddable(access=AccessType.FIELD)
public class History {
   Timestamp createDate;
   @Version
   Timestamp changeDate;
   //...
}

@Entity(access = AccessType.FIELD)
public class Article {
   //...
   @Embedded
   History history;
}
@Entity(access = AccessType.FIELD)
public class Order {
   //...
   @Embedded
   History history;
}

This way I have version info in all my Objects without subclassing. My need comes from a legacy database that could be easily modelled in hibernate with that construct (I didn't try this with h3 core, only with annotations, so I don't know if it works there).

christian · **Posted:** Thu Sep 22, 2005 11:19 am

Components don't have versions.

risc · **Posted:** Fri Sep 23, 2005 2:29 am

I don't see @Embeddable as a component, to me it is merely a boilerplate to construct part of an object.
As mentioned in my example above I have an existing database and try to reverse engineer that with ejb. The example corresponds to these tables:

Code:

Table Article
   id integer,
   ...
   createDate timestamp,
   changeDate timestamp

Table Order
   id integer,
   ...
   createDate timestamp,
   changeDate timestamp

The original database was created by a perl script that used such templates extensively to ensure consistent fields for all tables. Using @Embeddable does just this. Now changeDate is my only possible candidate for the version info so I would like to model that with @Version.

emmanuel · **Posted:** Fri Sep 30, 2005 3:55 am

So use @EmbeddableSuperclass and technical inheritance.