I know it is possible when A and B1 are mapped to one table. Not sure about when they are mapped to two tables. I would hope both would work since the only difference is in the mapping layer.
When they are mapped to one table... 1) Grab the A instance. 2) Create an instance of B1 and copy all attributes from the A instance. 3) Fill in B1 attributes. 4) Store. Later. Mitch -----Original Message----- From: Matt Mastrangelo [mailto:[EMAIL PROTECTED] Sent: Tuesday, October 21, 2003 8:45 AM To: OJB Users List Subject: Re: Inheritance mapping, storing new object associated with pre-existingsuper object Hi Gerhard, I'm not saying the B1 and B2 instances should extend the same instance of A, but that they should be materialized from the same A record in the database. B1 and B2 would have to be different objects obviously. I think this could be quite possible in OJB. But let me ask the question a different way - suppose I have an instance of A that already exists. Now I want to create a B1 instance that is associated with the already existing A instance. So I don't want a new A record to be created, only new B1 record that "extends" the pre-existing A record. Is that possible? Thank you for your input. Matt Gerhard Grosse wrote: >Hi Matt, > >Excuse me to jump in here, but I believe what you have in mind is not >possible in Java and even less with OJB. If your B1 and B2 instance >should 'contain' the same A instance as base class, they are identical >objects, which would require a language that supports multiple >inheritance (and virtual base classes). You could do that in in C++ >but not in Java. > >What you can do in Java (and OJB) is declare an interface I_A >implemented by A, B1 and B2. I_A just declares all public methods of A >and in B1 and B2 you implement this interface by delegation. That is >in B1 and B2 you have a reference to a A object and all I_A methods on >B1 and B2 are just routed to this reference. That way distinct >instances of B1 and B2 can easily share a common A reference. > >HTH, >Gerhard > >On Tue, 21 Oct 2003 00:27:02 -0400, Matt Mastrangelo ><[EMAIL PROTECTED]> wrote: > > > >>Chris, >> >>Just to clarify -- are you saying it's not possible to create the User >>instance without also creating a new Person instance? Maybe my example >>was not too clear. Let me re-explain: >> >>I have a base class A with two subclasses, B1 and B2. I have already >>created an instance of B1 and stored it to the database, which means >>that an A record and a B1 record were inserted. I now want to create an >>instance of B2 that extends from the same A record as B1. Is this possible? >> >>Thanks again. >> >>Matt >> >>[EMAIL PROTECTED] wrote: >> >> >> >>>Matt, >>> >>>I believe since the Person and Student object exist it will set there >>>values to null except the personId. Because in the User instance you are >>>storing allthe other fields are null (if you set them to null when you >>>declare them) except the loginName. So, ojb will know that person and >>>student 001 exist and will do and update instead of an insert. >>> >>>You should create them on the first store. Or do not have user extend >>>Student, instead have a 1:1 relationship. Depends on your requirments i >>>guess. >>> >>>-chris worley >>> >>> >>> >>> >>> >>>>I'm trying to figure out how to store a new persisted object that >>>>extends a pre-existing object. >>>> >>>>For example, I have 3 classes: Person, Student, and User. Student and >>>>User extend Person. A Student object already exists, and I now want to >>>>create a User object that inherits from the same Person as the Student >>>>object. Is this possible? Here's a code example: >>>> >>>>User user = new User(); >>>>user.setLoginName("matt"); >>>>user.setPersonOid("001"); // A pre-existing person >>>> >>>>broker.beginTransaction(); >>>>broker.store(user); >>>>broker.commitTransaction(); >>>> >>>>The result of the above code is a NEW empty person object being created >>>>with a newly generated OID (via a sequence). How can I associate the >>>>new User with a pre-existing Person? >>>> >>>>Thanks again. >>>> >>>>Matt >>>> >>>> >>>> >>>>--------------------------------------------------------------------- >>>>To unsubscribe, e-mail: [EMAIL PROTECTED] >>>>For additional commands, e-mail: [EMAIL PROTECTED] >>>> >>>> >>>> >>>> >>>> >>>> >>>--------------------------------------------------------------------- >>>To unsubscribe, e-mail: [EMAIL PROTECTED] >>>For additional commands, e-mail: [EMAIL PROTECTED] >>> >>> >>> >>> >>> >>> > > > >--------------------------------------------------------------------- >To unsubscribe, e-mail: [EMAIL PROTECTED] >For additional commands, e-mail: [EMAIL PROTECTED] > > > > -- Matt Mastrangelo X2 Development Corporation 781-740-2679 --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] ---------------------------------- The information contained in this e-mail message is intended only for the personal and confidential use of the recipient(s) named above. 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