Alex Smith wrote:
> Richard Monson-Haefel <[EMAIL PROTECTED]> wrote:
>
> >Bi-directional relationships create some interesting situations, when
> >concerned with establishing relationships between two participants. The
> >following scenario illustrates a problem that I would like vendors to
> >comment on, if they are up for the challenge.
> >
> >Assume that SalesRep has a one-to-many bidirectional relationship with
> >Customer.
> >
> >------------------
> >
> >SalesRep rep = SalesRepHome.findByPrimaryKey(somekey);
> >
> >Customer cust = CustomerHome.create( );
> >
> >cust.setSalesRep( rep);
> >
> >Colleciton colleciton = rep.getCustomers( );
> >
> >if(collection.contains( cust ))
> > flag = true;
> >else
> > flag = false;
> >
> >-------------------
> >
> >What is the value of flag? I suspect it should be true in this
> >scenario.
>
> The flag will be true only if the implementation of setSalesRep() does
> rep.add(this) where this is the Customer EJBObject. Alternatively if the
> sales rep => customer relationship has been established prior to this chain
> of events the flag will be true.
>
> Are you perchance after a mechanism where either side (rep -> customer,
> customer -> rep) of the relationship is automatically updated?
> If so, then I don't think containers do that: you have to "manually" update
> both sides. The convention is to do it from the one side (sales rep) in the
> many direction (collection of customers or in the session bean that wraps
> them.
This is interesting. You believe that the bean developer must manually set the
relationships and I believe that they must be set automatically by the
container. Why would the specification define these relationships in the
abstract persistence schema if you have to set them up "manually"? It doesn't
make sense. The container should automatically apply the other end of the
relationship when its bi-directional. For example, setting the SalesRep on
Customer should automatically add the Customer to the SalesRep's customers
relationship field. How do others interpret this?
--
Richard Monson-Haefel
Author of Enterprise JavaBeans, 2nd Edition (O'Reilly 2000)
Co-Author of Java Message Service (O'Reilly 2000)
http://www.jMiddleware.com
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