> -----Original Message-----
> From: A mailing list for Enterprise JavaBeans development
> [mailto:[EMAIL PROTECTED]]On Behalf Of [EMAIL PROTECTED]
> Sent: Friday, July 16, 1999 8:51 AM
> To: [EMAIL PROTECTED]
> Subject: Re: EJB with O/R mapping tool?
>
>
> [This didn't seem to make it the first time around. If you
> get two, sorry.]
>
> > From: Chuck Zheng [mailto:[EMAIL PROTECTED]]
> >
> > Hi Kevin,
> >
> > Which version of TopLink do you use? Their version 2 &
> Weblogic version
>
> We're using 1.1. Maybe 2.0 is better. I have no idea.
>
> > broucher looks impressive What's the fundamental flaw of
> their design
> you have found?
>
> Its inability to use a proxy/broker object to map another
> object is a fundamental
> flaw. It forces the creation of mapping methods on domain
> objects. The
> value-holder scheme they provide is not really useful for
> basically the
> same reasons; inflexibility and intrusion.
>
We have evaluated several tools, and TOPLink is defenitely less intrusive
then others. One of the classical approaches of OODBs and some O-R tools is
to post-process the bytecode. This is what I call intrusive...
Post-processing takes time which means that everytime you compile your class
you have to wait for post-processing to complete and it is also less robust.
I didn't get what kind of mapping methods you had to add to your model. BTW
in 2.0 they support private persistent attributes without set/get methods.
Not sure if this boethered you before.
> > What are the limitations?
>
> The only collection it supports is Vector. The least it
> could do is support
> Enumeration.
They now support Java 2 collections.
> The lack of support for aggregate inheritance mappings has
> caused us to
> have mapping methods in base classes. We have some base
> classes that have
> dozens of extra methods because of this.
Could you clarify. What's "aggregate inheritance mappings" ?
> Also, in 1.1, there is no way to query into an inheritance
> hierarchy. This
> means that you can only search on attributes that appear in
> the base class.
>
We have definitely used queries that included expressions on both inherited
attributes and leaf class attributes. Are you sure you had problems with
that.
> > What's the performance like (against Oracle 8)? Is it
>
> We are using Oracle 8, and all I can say is that it is slow.
>
> > possible to achieve
> > 50TPS for 1000 users system?
>
> I have no idea. All I can say is that, in some tests we ran,
> we found TOPLink
> to be roughly twice as slow as hand written JDBC. I believe
> TOPLink's documents
> back up this finding.
>
As I mentioned the 3 differnet O/Rs we have benchmarked had similar
performance. They all have significant (and similar) overhead on top of
JDBC.
Doron
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