XOM API for Processing XML with Java

[Michael Abato <mrabato AT earthlink.net>]

I suspect that using XOM objects in an EJB is going to lead to exactly the 
kind of mismatch of persistence techniques that justifies not making XOM 
persistent-capable in the first place (disclaimer: I'm not EJB wizard either, 
but I have dealt with this issue). I use XOM transiently to pull data out of 
the XML persistent stores and populate application-level data structures that 
are themselves persistent. I found this actually clarifies my application 
model as a side effect. The application level question about a field that is 
(was) a XOM Element (for example) boils down to "Is it part of an XML 
document or an application artifact?" It really can't/shouldn't be both.

Another approach to consider is to use XOM as the serialization format for 
the whole EJB. This would mean marking most everything transient and working 
with XOM in the persistence methods - persisting as one big string which 
happens to be valid XML. You lose the "magic" aspect of EJB serialialization 
(which I've never been a fan of in the first place...), but gain tremendous 
control over the persistence process. Any non-trivial code which interacts 
with complex external resources (like XML files you would likely have read 
in) has to deal with the murky details of all this, anyway.

Michael Abato

-----Original Message-----
From: Rich Sezov <sezovr AT yahoo.com>
Sent: Feb 4, 2004 7:10 AM
To: Elliotte Rusty Harold <elharo AT metalab.unc.edu>
Cc: xom-interest AT lists.ibiblio.org
Subject: Re: [XOM-interest] Use in EJBs

--- Elliotte Rusty Harold <elharo AT metalab.unc.edu>
wrote:

> reasonable alternative. For example, is there some
> reason you can't 
> implement your own subclasses of the XOM classes
> that do implement 
> Serializable? 

Yes; I could probably do that. It's a trade-off,
though. I was recently re-introduced to the
complexities of using the DOMParser to parse out my
XML, since I couldn't use XOM to do it in my EJB, so
the choice is: will it take me longer to subclass all
the stuff I'm going to use out of XOM, or to rewrite
my methods using the DOMParser that comes with Xerces?
Plus, that's sort of a hack, isn't it? 

I'm sort of new to XML parsing in general (and EJBs,
for that matter--this one is my first), so I can't say
I've tried all that many things. Maybe this is like
the blind leading the blind here. :-)  But the
DOMParser classes must be Serializable (disclaimer: I
haven't looked at the source) because I can use that
API just fine in an EJB. 

I agree with you that developers shouldn't abuse the
Serializable interface by writing out the objects
themselves to disk, but use in an EJB, I think, is a
legitimate reason to implement it. 

=====
Rich Sezov


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