Jonathan,
Of course, products like TOPLink (and others...) have been doing this type
of thing for years with "non-EJB" objects so I don't necessarily agree that
optimistic locking (i.e., parallel transactions) cannot be done without a
POA-like framework (though I do agree that the POA probably makes this easier).
Just my two cents,
Robert
At 02:35 PM 4/19/00 -0700, you wrote:
>Ah, the joys of quoting out of context and out of date. We will
>update our FAQ appropriately. The below quote is a version of
>something I wrote discussing our Alpha product back in the fall
>of 1998. At that time, the only relevant EJB containers on the
>market were WebLogic and WebSphere, and I was referring to those
>product. The fact is that now, a year and a half later, some
>other EJB containers do support multiplexed dispatching for parallel
>transactions.
>
>However, I will contend that supporting this feature requires running
>on something functionally equivalent to a POA. Yes, you can build a
>POA-like infrastructure on top on a BOA (I have) but it is messy and
>quite complicated (at least mine was). It is in fact just about as
>hard as implementing the POA altogether (again, something I have
>been involved with).
>
>The basic problem is that simpler dispatching models assume that the
>object key is sufficient to locate the server-side object. In EJB,
>for entity beans, to implement optimistic concurrency, you need to
>dispatch on both the object key and the transaction id. Which can
>be complicated because you may not know what is the current transaction
>until you look at its deployment descriptor (the entity could be running
>in the callers transaction, or could be running in a new transaction)
>which requires knowing what the object is going to be.
>
>Again, this is what the POA is designed to support. Building it from
>scratch is non-trivial. This is "why [many] other EJB containers [still
>do not] provide this functionality", even today.
>
>-jkw
>
>Evan Ireland wrote:
> >
> > "Louth, William (Exchange)" wrote:
> > >
> > > Hi Robert,
> > >
> > > In the inprise documentation they do elaborate on this association a bit
> > > more:
> > >
> > > Sidebar:
> > > Implementing this parallel transaction feature is non-trivial for
> most EJB
> > > container vendors, because it requires a relatively sophisticated
> > > server-side object dispatch model. What is required is the ability to
> > > dispatch on a server-side object using both the primary key (which is
> > > usually embedded in the object reference) and the current
> transaction. Doing
> > > this multi-key dispatch is very hard to implement on top of an RMI or BOA
> > > style server-side model, which is why no other EJB container provides
> this
> > > functionality. We leverage the POA, which is a server- side
> frame-work which
> > > is much more sophisticated, and which is much more conducive to
> implementing
> > > this functionality.
> >
> > The Inprise technical writers would be well-advised not to make
> unsubstantiated
> > claims about "other EJB" containers. They are wrong.
> >
> __________________________________________________________________________
> ______
> >
> > Evan Ireland Sybase EAServer
> Engineering [EMAIL PROTECTED]
> > Wellington, New Zealand +64 4
> 934-5856
> >
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>
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