Hi Hunter.
They are by no means thought of as worthless. However, there was a debate
about whether or not they were the best way to accomplish what they did
accomplish.
As you probably know, EJB 1.1 has a serious deficiency in that it does not
support relationships between EBs well. If you want to refer to an EB from
another EB, you have to serialize its remote interface of primary key into
binary field in the database.
EJB 2.0 supports relationships between EBs, but using the remote interface
was an expensive way for EBs to manipulate each other. A developer would
hesitate to model his entity with several objects because of this overhead.
A DO allowed a developer to implement data in an EB in a seperate table and
still be part of the bean, with no remote interface. So it was an
implementation feature, not a design feature. So, if you had a Person EB
you could have an Address DO. The Person would be in one table and the
Address in another. The Person EB had access to the Addrss with little
overhead. Other EBs lacked access to the DO.
This is nice, but forces the designers to consider implementation at design
time. Thats bad.
The new sollution is to allow EBs to interact using a "local" interface, as
opposed to a "remote" interface. The local interface lacks the overhead of
the remote interface. Its a big improvement. From a design standpoint, your
objects are objects. Not perfect, but better.
I was upset when DOs were removed. ut I now admit this local interface
stuff is a better sollution.
Jim
--On Tuesday, May 29, 2001 10:41 AM -0700 Hunter Hillegas
<[EMAIL PROTECTED]> wrote:
> I remember quite a few folks being glad that DO's got removed from the
> EJB2.0 spec...
>
> I'm reading the MVCSoft manual which still contains them and I'm trying to
> remember why they were considered worthless... Is there something else
> that does the same thing?
>
> Hunter
>
>
> _______________________________________________
> JBoss-user mailing list
> [EMAIL PROTECTED]
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