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From "James.Strachan" <james.strac...@gmail.com>
Subject the pain of post processing bytecode (another beg for a simple reflection/cglib alternative like hibernate)
Date Thu, 17 May 2007 09:39:52 GMT

Firstly before I start, openjpa is a great piece of software; I'm
particularly fond of the documentation and in particular the query language
parts. The CSS for the site is also awesome :)

However compared to hibernate, openjpa is still pretty painful to use from
an end users perspective and I don't think this should be the case; plus I
don't think it'll take much time to fix. While the pain is still fresh in my
mind I thought I'd post on how much more painful openjpa is to use in a
project. If you're short on time, the basic idea is its that bytecode post
processing stuff thats to blame :). Yes I know its probably faster that way
- its just so painful for Java programmers to work with. (And yes I know one
day we'll all have IDE plugins that hide the bytecode stuff etc etc).

So the first thing is having to mess with your build (ant or maven) to get
the post processing properly integrated. Depending on if you have persistent
entities in your main or test area this can often trip you up a little (as
it did me). I don't know about folks on this list but the whole idea of
having to mess with my maven build gives me the jitters :). When you get
that far & the maven planets are aligned with openjpa, the next hurdle you
hit is how do you run stuff in your IDE. If like me you use IDEA and maven
2, the project gets auto-created by default for all projects you work on.
However these don't work when you use openjpa as you hit the dreaded 'cannot
function at all as you've not run the up front bytecode post processor you
dummy!' type error when trying to run stuff in your IDE.

So you then add the maven-generated classes to the front of the classpath in
your project. Hooray, after a day or two's work, you can now actually use
openjpa in your IDE and your build. YAY! The downside is that now when
navigating around your Java code, whenever you navigate into an entity bean,
IDEA shows you the bytecode - not the source code as its confused since the
bytecode generated stuff is different to the source code it knows about. So
now you're faced with a dilemma - choose between navigating nicely around
your source code - or being able to actually run/debug your application. I
won't even get into the refactoring pain or having to continuously run maven
builds while developing code to avoid getting code completion/compile errors
etc. (I prefer to keep in my IDE where possible).

Compare this whole malarkey with hibernate. You add hibernate to your pom,
generate your project and you're good to go. No messing with your project
build; no messing with some secret ninja IDE stuff to be able to actually
run & debug your code while still being able to actually navigate the
source. It just works. Now it might work in a crappy & slow way and openjpa
might be way way more efficient and powerful and whatnot - but I'd rather
have a cheap car that just works than a ferrari that you can only drive on a
tuesday if its sunny, but not too hot and refuses to even start if its wet.

FWIW I've just given up using openjpa for development; its just way too
painful. (I'm even hacking projects I work on so I use openjpa in the maven
build but explicitly switch to hibernate in development mode; yeah its more
work but at least I can use my IDE properly again).

I'm cool with putting post processing into the build system (though that
should really only be an optimisation); but please can we have some
inefficient but usable reflection/cglib type approach so folks can easily
switch from hibernate to openjpa (and stay there) without pulling out our
hair & swearing too much - or sneaking back at the first opportunity to get
an easy life?

Please don't take this mail the wrong way - I truly want openjpa to be a
success, its a great piece of software. Its just a bit too hard to use out
of the box right now. I'd truly like it to be trivial to switch from
hibernate to openjpa and never have to go back. 

How hard is it to add a reflection/cglib type alternative to the upfront
bytecode generation (like hibernate does) to save us from the
development-time pain?

-- 
James
-------
http://macstrac.blogspot.com/

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