TABLE_PER_CLASS warning - also need example of this mapping

damonf · **Joined:** Wed Dec 21, 2005 6:57 pm **Posts:** 70

Using TABLE_PER_CLASS (unfortunately) we are having an issue converting to annotations. Here are the mappings for two of the classes in the hierarchy:

Hibernate version:
core 3.2.5, annotations 3.2.1

Mapping documents:

Code:

@Entity 
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
@Table(name="value") 
@Proxy(lazy=false) 

@Entity 
@Table(name="stringvalue")
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
@Proxy(lazy=false) 
@Embeddable
@PrimaryKeyJoinColumn(name="cdfvalue_guid")

(we added the @Inheritance annotation to the subclass, but have also tried it without that annotation)

Here is the Warning output we get

Code:

    [exec] 21:27:04,515 WARN  [AnnotationBinder] Root entity should not hold an PrimaryKeyJoinColum(
s), will be ignored
    [exec] 21:27:04,515 WARN  [AnnotationBinder] Root entity should not hold an PrimaryKeyJoinColum(
s), will be ignored

What does this error mean? If the PrimaryKeyJoinColumn does not join up the superclass table with the subclass tables, how should we specify the join?

The annotation docs do not fully document this mapping style (only the superclass mapping is indicated). Can someone point us to an example of TABLE_PER_CLASS, or post a working mapping with annotations?

emmanuel · **Posted:** Sat Mar 08, 2008 1:11 pm

TABLE_PER_CLASS does not need any PKJC information. What are you trying to map here?

damonf · **Joined:** Wed Dec 21, 2005 6:57 pm **Posts:** 70

I have a list of user-defined values that can be strings or numbers. The superclass has data like the value name, etc. and the sub-classes hold a numeric or a string value, respectively.

The sub-class tables have a key that is the same as the parent GUID.

I have written DB scripts to move the data up into the parent table and will change to table-per-hierarchy (which should have been used in the first place), but for the overall community it would be good to post an example of the mapping. The annotations docs (section 2.2.4.1) only show how to annotate the superclass, but don't show an example of how the subclasses are annotated. I'd say it's a doc bug.

Do they just use the PKs of both classes, assuming that it is a joing on PK? Do people need to specify the strategy at the subclass level as well? etc.

Here are the old mappings:

Code:

*        @   <<removed>> hibernate.class
 *         table="customvalue"
*/
@Entity 
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
@Table(name="customvalue") 
@Proxy(lazy=false) 
public abstract class CustomValue

@Entity 
@Table(name="customstringvalue")
@Proxy(lazy=false) 
@Embeddable
@PrimaryKeyJoinColumn(name="customvalue_guid")
public class CustomStringValue extends CustomValue 

thanks for taking time to post a reply!

emmanuel · **Posted:** Mon Mar 10, 2008 7:19 pm

open a JIRA issue for the doc enhancement.

Basically, just get rid of @PrimaryKeyJoinColumn. There is no FK involved in a table per class. For a given instance, the data is in one and only one table.