Hi Markus,
It's possible but you need to map the same column twice - once as an id, and
another time as the relationship field. Look at the Order-LineItem example in
the Java EE 5 Tutorial.
Regards,
-marina
Markus KARG wrote:
> Tom,
>
> it seems you are right with your interpretation of the JPA specification.
>
> As a result, that means that it is impossible to use JPA to access
> databases that have a foreign key constraint inside of the primary key.
> Or did I oversee a possible solution other than replacing the entity
> reference by a set of simple generic types?
>
> Thanks
> Markus
>
>> My understanding is that putting @Id on a relationship field is not
>> supported by version 1.0 of the JPA specification. If you look at
>> section 2.1.4 of the specification it is quite specific about only
>> allowing primary keys to be composed of primitive types:
>>
>> "The primary key (or field or property of a composite primary key)
>> should be one of the following types:
>> any Java primitive type; any primitive wrapper type; java.lang.String;
>> java.util.Date;
>> java.sql.Date. In general, however, approximate numeric types (e.g.,
>> floating point types) should
>> never be used in primary keys. Entities whose primary keys use types
>> other than these will not be portable.
>> If generated primary keys are used, only integral types will be
>> portable. If java.util.Date is
>> used as a primary key field or property, the temporal type should be
>> specified as DATE."
>>
>> I have heard some rumors that this is under discussion for the next
>> version of the specification, but to be honest I am not sure. I
>> suggest sending a request to the expert group. I am not sure what the
>> exact email address is, but perhaps someone on this forum will be nice
>> enough to post it.
>>
>> -Tom
>>
>> Markus KARG wrote:
>>
>>> I think I found a bug in TopLink and want to discuss with you before
>>> hastily reporting it officially.
>>>
>>> There is one entity that has a compound key made up of two fields,
>>> and it has a sub-entity using @Inheritance(strategy = JOINED). I can
>>> insert new rows using the super class directly, but when I want to
>>> use the sub-class, TopLink produces a SQL INSERT statement that just
>>> fills one of the compound key's fields -- and forgets the other one!
>>> Certainly the database server complains about that.
>>>
>>> In fact, I'd like to know whether that is a real bug or whether I am
>>> doing something wrong (in that case, please tell me what I am doing
>>> wrong and where in the JPA specification that is told).
>>>
>>> Here is the interesting part of the source code:
>>>
>>> @Entity
>>> @Inheritance(strategy = JOINED)
>>> public abstract class TheSuperClass {
>>>
>>> @Id
>>> @ManyToOne
>>> private Invoice invoice; // TheSuperClass actually is part of an
>>> Invoice
>>>
>>> @Id
>>> private int position; // Inside of the Invoice, we identify
>>> multiple instances using this int
>>>
>>> ...
>>>
>>> @Entity
>>> public final class TheSubClass extends TheSuperClass { // TheSubClass
>>> is a specialization of TheSuperClass
>>>
>>> (there is no additional code in this class, since it I stripped away
>>> everything for this small sample)
>>>
>>>
>>> I am totally stuck with that problem. Please help me. :-)
>>>
>>> Thanks
>>> Markus
>>>
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: users-unsubscribe_at_glassfish.dev.java.net
>> For additional commands, e-mail: users-help_at_glassfish.dev.java.net
>>
>
>