xml-dev - Re: Sun XML early access

[Tyler Baker <tyler@infinet.com>]

Michael Kay wrote:

> >Has anyone had a chance to look at the early access Sun XML
> package yet?
> >I'm just starting my explorations, and (so far, to me) it
> looks pretty
> >intriguing.  The DOM interface is promising, and I'm very
> glad to see SAX
> >support.
>
> I've been testing it with SAXON. Some hiccups, as yet
> unresolved, but generally promising. Performance is in the
> same league as xp and AElfred. They've done some interesting
> things with the DOM, for example the ability to nominate
> user-defined subclasses of Element, and a TreeWalker
> interface. This is where SAXON started last December!
>
> Actually I'm not sure subclassing Element with a "semantic"
> subclass, e.g. a business object such as Invoice, is the
> right approach, because you get a clumsy class heirarchy,
> and you invite the user to override methods inappropriately.
> I'd prefer to have the Element contain a "userObject"
> pointer to the business object.

I pretty much never ever subclass anything for typing purposes except as a code
reuse policy.  I have already learned the hard way that this sort of approach
builds highly inflexible and highly inefficient systems.  It forces you to build
upon previous implementations of superclasses that may have crappy
implementations.  If you are strict in doing all your typing with interfaces, you
can rewrite entire parts of systems (if necessary) without having to change your
code in any of your other systems.  Every major Java ISV out there seems to get
this other than SUN who still seems to prefer the subclassing approach in their
designs.  Maybe this is for some potential purpose of vendor lock in.  Who really
knows.

Tyler


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