Persisting an embedded object that contains a collection of

[ceracm]

I have an embedded object that contains a collection of entities:

@Entity(access=AccessType.FIELD)
class Foo {
@Embedded
private Bar bar;
}

@Embeddable(access=AccessType.FIELD)
class Bar {
 private Collection<Baz> baz
}

@Entity
class Baz {}

I want the following mappings:
* class Foo to table Foo
* class Baz to table Baz
* The one-to-many should be mapped to a foreign key in table baz to table Foo
* Class Baz is essentially mapped to table Foo (although it doesn't have any fields)

I have two questions:
1. What annotations should I write according to the EJB 3.0 spec?
2. Does JBoss eJB 3.0 preview 4 support it?

Thanks

[epbernard]

This is not supported by the EJB3 spec. But the preview 5 should allow you to write something like that

@Embeddable(access=AccessType.FIELD)
class Bar {
 @OneToMany
 @JoinColumn(name="foo_id")
 private Collection<Baz> baz
}

Note that this kind of mapping is not recommanded. Use a join table for such unidirectional one to many.

[ceracm]

"epbernard" wrote:
This is not supported by the EJB3 spec. But the preview 5 should allow you to write something like that

@Embeddable(access=AccessType.FIELD)
class Bar {
 @OneToMany
 @JoinColumn(name="foo_id")
 private Collection<Baz> baz
}

Note that this kind of mapping is not recommanded. Use a join table for such unidirectional one to many.

Thanks for the suggestion.

Is this this explicitly disallowed in the EJB3 spec?
I couldn't really see anything.

Please could you explain why you recommend a join table instead of a foreign key mapping.

[epbernard]

"ceracm" wrote:
Is this this explicitly disallowed in the EJB3 spec?
I couldn't really see anything.

Please could you explain why you recommend a join table instead of a foreign key mapping.

The spec restrict the allowed mapping annotations in a embeddable object AFAIR.

99% of the @OneToMany cases should use a bidirectional mapping at the object level. If for some good reasons it is explicitly unwanted, then these reasons should encourage you to decouple the 2 entities (from a DB POV) through a join table.