RE: [Objectbridge-jdo-dev] Instrumentation/Enhancement pros and cons

[Jim H. <je...@hu...>]

Hi.  My name is Jim Hughes, and I hope to be able to contribute in some
way to this project.

Anyway, my understanding is that if we do enhancement, the way we do it
is pretty well specified, if we want to comply with the spec, that is.
Classes need to be modified to implement PersistenceCapable, etc.  The
spec even states that enhanced classes must be portable between
different JDO impls, which really constrains us.  E.g., we couldn't do
this:

// way pseudo!
package org.objectbridge.jdo;
interface PersistenceCapable extends javax.jdo.PersistanceCapable
{
	void persistYourself() ;
}

public class PersistenceManager implements javax.jdo.PersistanceManager
{
	void makePersistent(Object o)
	{
		PersistenceCapable pco =
(org.objectbridge.jdo.PersistenceCapable)o;
		pco.persistYourself();
	}
}

because this code would not work with PersistenceCapable class enhanced
by other impls.

I would be interested in working on the enhancer.  Is anyone working on
it yet?

Jim


-----Original Message-----
From: obj...@li...
[mailto:obj...@li...] On Behalf Of g
Sent: Monday, March 04, 02 10:48 AM
To: obj...@li...
Subject: [Objectbridge-jdo-dev] Instrumentation/Enhancement pros and
cons


Hi all,
	I have been reading up on the controversy over some of JDO's
features, and have reaqd some of the postings on this list regarding
JDO. I understand and agree with the concerns of some people who have
found that classees that have been enhanced through byte code
instrumentation may behave unpredictably, for example when debugging
information is lost, mangled, or not properly inserted into an
instrumented class file. The seemingly mysterious nature of this
instrumenting process does evoke a sense of worry, but I have not seen
any discussions of what the alternatives are.

Have we as a group had any discussion about how we might avoid choosing
the abovementioned approach? Perhaps a compromise like inserting just
enough code into the enhanced class to provide proper identity
attributes, which would enable us to use metadata accessed from behind
the facade of the PersistenceManager?

I have some experience with the BCEL byte code libraries, and have some
code that traverses compiled code and can do analysis or make changes.
This code uses BCEL. It's pretty straightforward.

Thanks,

George Coles


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