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From "Kevin Sutter (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (OPENJPA-2126) Default join table column name in many-to-many relationship does not follow JPA v2 specification
Date Wed, 22 Feb 2012 16:01:48 GMT

    [ https://issues.apache.org/jira/browse/OPENJPA-2126?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13213724#comment-13213724
] 

Kevin Sutter commented on OPENJPA-2126:
---------------------------------------

My guess is that the introduction of the Map type and @MapKey annotation is confusing this
name resolution.  If you change the type of owners to a standard Collection, I bet the name
generation is correct.  Looking through the spec, it's not clear on the naming expectations
when using a Map.  The only reference is this sentence in section 2.7.2:

"When the value type of the map is an entity, a join table is used to map the map for a many-to-many
relationship.."

But, I can't find any naming generation rules when the @ManyToMany is being represented by
a Map.  I've also searched other references to find general guidelines without any luck. 
Since you always have the ability to override the defaults via the @JoinTable annotation,
I'm not sure we would entertain changes in this area.  Unless we can determine a more definitive
explanation of the naming requirements.

Thanks,  Kevin
                
> Default join table column name in many-to-many relationship does not follow JPA v2 specification
> ------------------------------------------------------------------------------------------------
>
>                 Key: OPENJPA-2126
>                 URL: https://issues.apache.org/jira/browse/OPENJPA-2126
>             Project: OpenJPA
>          Issue Type: Bug
>          Components: jdbc, jpa
>    Affects Versions: 2.1.1
>            Reporter: Maria Jurcovicova
>
> According to JPA v2 specification page 48, the joining table should have two columns.
One column should have foreign key to owners table and the other should have foreign key to
the inverse table. 
> The name of the column referencing the owner should be:
> * the name of the relationship property or field of inverse entity ; 
> * underscore "_";
> * the name of the primary key column in owner table. 
> OpenJPA assumes that the name of  the column referencing the owner is:
> * owner entity name ; 
> * underscore "_";
> * the name of the primary key column in owner table. 
> The name of the column referencing the inverse is correct.
> Example entities:
> @Entity
> @Table(name="tblMtmOwner")
> public class MtmOwner {
>   @Id
>   private long id;
>   private String name;
>   @ManyToMany
>   private Collection<MtmInverse> inverses = new ArrayList<MtmInverse>();
> }
>  
> @Entity
> public class MtmInverse{
>   @Id
>   private long id;
>   @ManyToMany(mappedBy="inverses")
>   @MapKey(name="name")
>   private Map<String, MtmOwner> owners = new HashMap<String, MtmOwner>();
> }
> Expected column name: owners_id
> OpenJPA column name: mtmowner_id 

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