FYI ----- Original Message ----- From: "Sean Neville" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, March 08, 2001 4:34 PM Subject: Re: Article on dependent objects > Dependent objects have already been marked for removal from the spec; > moreover, local entities -- probably at least as controversial -- have been > introduced both as a partial replacement for pieces of the dependent object > concept and to solve the need to permit parameter pass-by-reference. > > I would guess that the next pfd of the spec (and probably another article > from Tyler, followed by another series of intelligent reviews from Dan, > Gene, and others on this list) should surface by late April, but in the > interests of spreading the info as early as possible to those who don't > happen to work for a vendor and thus already have this info (power to the > people), here is a quick and completely unofficial description of local vs. > remote EJB's as posed to us in another discussion. It is obviously subject > to change, and only the EJB and J2EE specs are in any way definitive. > > Local > ----- > Access only with scope of PM > No Transaction attribute > No Security check > Can expose CMP and CMR fields and local refs > PBR parameters > Local exception model > Signatures use full Java type system > Typically fine grained methods > High coupling due to PBV side affects and fine grained exposure > > Remote > ------ > Global access > Requires Transaction attribute > Requires Security check > Prohibits exposure of CMP and CMR fields and local refs > PBV parameters > Container interposed exceptions > Signatures restricted to RMI-IIOP compatible types > Typically coarse grained methods > As loosely coupled as a procedural object can get > > > > -----Original Message----- > From: A mailing list for Enterprise JavaBeans development > [mailto:[EMAIL PROTECTED]]On Behalf Of Dan Christopherson > Sent: Friday, March 02, 2001 12:47 AM > To: [EMAIL PROTECTED] > Subject: Re: Article on dependent objects > > > On Thu, 1 Mar 2001, Alex Smith wrote: > > > Dan O'Connor <[EMAIL PROTECTED]> writes: > > > > >Tyler Jewell, the BEA training director for Java and XML > > >technologies, yesterday published an article called "What's Wrong > > >with the EJB 2 Specification" at > > >http://www.onjava.com/pub/a/onjava/2001/02/28/ejb.html. In this > > >article, he identifies "dependent objects" as what is wrong with the > > >EJB 2 specification. > > > > Good article. I do agree that Tyler's objections are misplaced. > > > > >First, I would like to correct what I believe was a fairly basic > > >technical mistake in Tyler's article. He says, "Dependent objects > > >don't require primary keys." I would like to suggest that the > > >opposite is the case, and I cite from 9.4.4.1 in the spec (proposed > > >final draft): "The dependent object class instance must have a > > >primary key value that is unique across all instances of the > > >dependent object class." > > > > This is a mistake in the spec rather than the article -- dependent objects > > should not have an identity of their own else they would no longer be > > dependent. If you use a relational model to color your perception of the > > world, a dependent object may or may not have its "own" (i.e. not composed > > from the keys of its parent) primary key. Some data modeling methodologies > > recommend creating a unique physical key for each and every entity, a > > practice I don't subscribe to. On the other hand if you think in terms of > > objects, a dependent object belongs to the parent and therefore cannot > have > > an identity other than that of its parent. > I'd say that the dependent object has no identity that is meaningful > outside of the context of its parent. If you have three dependent > instances of the same class associated with the same parent, they must > have their own identities if you do not consider them equivalent, right? > > > > > I think the spec should provide support for dependent objects with a > primary > > key but not require it. > > > > The rest of Dan's comments are right on target. > > > > Alex Smith > > Insight LLC > > _________________________________________________________________ > > Get your FREE download of MSN Explorer at http://explorer.msn.com > > > > > =========================================================================== > > To unsubscribe, send email to [EMAIL PROTECTED] and include in the > body > > of the message "signoff EJB-INTEREST". For general help, send email to > > [EMAIL PROTECTED] and include in the body of the message "help". > > > > -- > Dan Christopherson (danch) > nVisia Technical Architect (www.nvisia.com) > > Opinions expressed are mine and do not neccessarily reflect any > position or opinion of nVISIA. > > --------------------------------------------------------------------------- > If you're a capitalist and you have the best goods and they're > free, you don't have to proselytize, you just have to wait. > -Eben Moglen > > =========================================================================== > To unsubscribe, send email to [EMAIL PROTECTED] and include in the body > of the message "signoff EJB-INTEREST". For general help, send email to > [EMAIL PROTECTED] and include in the body of the message "help". > > =========================================================================== > To unsubscribe, send email to [EMAIL PROTECTED] and include in the body > of the message "signoff EJB-INTEREST". For general help, send email to > [EMAIL PROTECTED] and include in the body of the message "help". > > =========================================================================== > To unsubscribe, send email to [EMAIL PROTECTED] and include in the body > of the message "signoff EJB-INTEREST". For general help, send email to > [EMAIL PROTECTED] and include in the body of the message "help". > -- -------------------------------------------------------------- To subscribe: [EMAIL PROTECTED] To unsubscribe: [EMAIL PROTECTED]
