On 2002.12.05 23:36:21 -0500 tek1 wrote: > hi david. > > thank you very much for your reply. > > i was considering using xdoclet's generateGUID() method to generate > random > id's for the entities/records, but this appears to break down in jboss' > horizontal positioning approach, unless in the ejbCreate() method for the > > SUBCLASS, it checks to see if the id generated by generateGUID() exists > in > the PARENT entity/table. > > does this sound correct?
I dont' knwo how it works. If it can generate collisions I don't really see why "GUID" is in the name. I'd use a generator/sequence from the db and make sure all tables use the same generator. david > > thanks again. > > > At 23:11 02/12/05 -0500, you wrote: > >At the moment jboss figures the BASE and EXTENDED entity beans are > >unrelated and is happy if they have the same id. I've been trying to > get > >some discussion going about how to support polymorphic entity beans in > >jboss, but so far haven't had much response. > > > >JBoss 4 will be able to map an entity to more than one table, so the > >vertical partitioning (and presumably the typed scheme) will be > possible. > > > >you are pretty much on your own for generateing pk values anyway, so you > >can choose a scheme whereby BASE and EXTENDED don't share numbers. > > > >david jencks > > > > > > > >On 2002.12.05 21:22:01 -0500 tek1 wrote: > > > hi marc! > > > > > > thank you for the clarification. > > > > > > the reason why i asked is because if jboss uses horizontal > partitioning, > > > is > > > it possible for the same id to be used for different objects in > different > > > tables? > > > > > > for example, given the following tables: > > > > > > BASE > > > -oid > > > -name > > > > > > EXTENDED > > > -oid > > > -name > > > -age > > > > > > > > > if in BASE, the following record exists: > > > > > > BASE > > > oid | name > > > ---|----- > > > 1 | marc > > > > > > and we want to add a new record (entity instance having different > data) > > > to > > > EXTENDED, does jboss know not to use an oid of "1" in EXTENDED, since > it > > > already exists in the BASE table? > > > > > > also, how can one protect against outside access of the db (i.e. > using a > > > db > > > management/sql tool) from someone inserting records with the same id > (but > > > > > > different data) into BASE and ENTITY? it seems like this opportunity > for > > > > > > error is prevented with the vertical partitioning approach, but not > with > > > the horizontal partitioning approach. does jboss compensate somehow > for > > > this? > > > > > > thank you again. > > > > > > > > > > > > At 18:28 02/12/05 +0100, you wrote: > > > >Hello, > > > > > > > > > when one entity bean extends another, does the extending entity > > > bean's > > > > > table include all of the fields of its parents in its own table? > > > > I don't know how this is solved within JBoss, but > conceptually > > > you > > > >have three possibilities: > > > > > > > > #1 - typed partitioning > > > > > > > > the sum of all fields are stored in a base table, having an > > > >additional column defining what kind of object it is: base, or > extended. > > > > > > > > for instance > > > > > > > > BASE > > > > String name > > > > > > > > EXTENDED > > > > int age > > > > > > > > would result in the table BASE having > > > > oid INTEGER - object identifier > > > > name VARCHAR > > > > age INTEGER > > > > objType INTEGER (or some kind of IDENTIFIER) > > > > > > > > > > > > #2 - horizontal partitioning > > > > > > > > all fields are repeated in each table for the subclasses. > > > > > > > > this would result in a table EXTENDED with oid, name and > age, > > > and in > > > >a table BASE with oid and name. > > > > > > > > > > > > #3 - vertical partitioning > > > > > > > > only the very fields belonging to the class are stored in > the > > > >corresponding table > > > > > > > > this would result in a table BASE with oid and name, and in > a > > > table > > > >EXTENDED with oid (also referencing BASE(oid)) and age. > > > > > > > > > > > > > when i deployed 2 entity beans, one extending the other, the > > > extending > > > > > bean's db table had all the fields defined of its parents' > table... > > > > then JBoss adopted the horizontal solution... > > > > > > > > > > > > Regards, > > > > > > > > Marc > > > > ------------------------------------------------------- > This sf.net email is sponsored by:ThinkGeek > Welcome to geek heaven. > http://thinkgeek.com/sf > _______________________________________________ > Xdoclet-user mailing list > [EMAIL PROTECTED] > https://lists.sourceforge.net/lists/listinfo/xdoclet-user > > ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf _______________________________________________ Xdoclet-user mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/xdoclet-user
