On May 17, 2007, at 5:31 PM, David Ezzio wrote:
I think that the issues raised are best solved with tools, documentation, and examples.Of course, if one has been coding to Hibernate for years, it's unlikelythat any combination of tools, documentation, and examples will make OpenJPA easier to use for that person, but that's not the standard.
Sure it will. If you are using one JPA implementation, be it Hibernate, Toplink, or anything else, and you want to "drop in" OpenJPA to test it out and see what the performance difference is, if it doesn't work immediately, you are likely to walk away.
I think that easing the process for someone already familiar with JPA to get started with OpenJPA without having to pour through documentation about build-time tools or runtime agent flags is a supremely useful project, especially at this point where we are on the brink of graduation and will soon be getting a lot more attention.
Another important point, in my view, is to make sure the tests run as well on Windows (without cygwin!) as they do on Linux, Unix, and OS/X.For example, using File.separator to construct resource path names worksgreat on everything but Windows.
This seems orthogonal to the issue of easing OpenJPA's bytecode enhancement process. If you find cases where we are relying on hardcoded UNIX paths, these are obviously bugs and should be handled by creating JIRA issues.
David Marc Prud'hommeaux wrote:I think this is a very worthwhile project. James and a few othersexcoriated me about this issue over beers after JavaOne last week, and, while the bruises from their rhetorical assault are still healing, their observations about the comparative "out of the box" ease of use OpenJPAcompared to other systems definitely bears attention. As Patrick mentioned, we aren't too far away from being able to use a dynamic subclassing approach.Another option I've been thinking about recently is that in JDK 1.6, youcan dynamically attach an agent at runtime to your own JVM (using an implementation-specific mechanism), and using the provided Instrumentation, you can redefine existing methods in classes, even after the classes have already been loaded. While you cannot add orremove methods or fields, we might be able to re-work our PCEnhancer to use a newly-generated inner class and a lookup in some IdentityHashMapto perform the same function. E.g., instead of our currently enhanced class: public class SomeEntity { private String someField; private StateManager stateManager; // generated public String getSomeField() { return pcgetSomeField(this); } // generated method private static String getSomeField(SomeEntity entity) { if (entity.stateManager == null) return entity.someField; else entity.stateManager.getField(1, entity); } } we would instead do something like: public class SomeEntity { private String someField; public String getSomeField() { return GeneratedInnerClass.pcgetSomeField(this); } private static class GeneratedInnerClass { private static String getSomeField(SomeEntity entity) { StateManager stateManager = GlobalIdentityMap.get(entity); if (stateManager == null) return entity.someField; else stateManager.getField(1, entity); } } }From the brief amount of time I've spent thinking about this, I thinkwe can get 99% of the way there with our current approach.The remaining 1% is a situation where if someone creates an instance ofSomeEntity *before* we ever initialize the BrokerFactory (and thusperform the re-definition of known entity classes), we might get passed an entity instance that isn't persist-able (since you cannot redfine themethods for an already-created object, only for objects that will subsequently be created). In summary, we have 3 different possibilities for removing therequirement for build-time enhancement and launch-time agent specification:1. Use reflection: considerably slower, would require drastic rework ofall our interaction with PersistenceCapable instances, but wouldn't require any fancy class-generation/enhancement2. Dynamic subclassing: easier to implement, but would require people touse property accessors for everything, and wouldn't support EntityManager.persist(someInstance)3. Dynamic agent attachment and class re-definition: more difficult toimplement than #2, and would require JDK 1.6 + JVM implementation-dependent attachment mechanisms, but might provide the most functionalityDoes anyone have any thoughts about this? Especially any new ideas for other ways to do this would be very interesting for all of us to hear.On May 17, 2007, at 8:19 AM, Patrick Linskey wrote:How hard is it to add a reflection/cglib type alternative to the upfrontbytecode generation (like hibernate does) to save us from the development-time pain?Not particularly hard. There are a few APIs that would break for somecases, but it's even pretty straightforward to do a subclassing approach for property-based access type without losing much performance -- the only cost in that configuration is with persistent-new instances. -Patrick On 5/17/07, James.Strachan <[EMAIL PROTECTED]> wrote: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 usefrom 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 mymind 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 bytecodepost 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 oneday 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 (asit 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 getthat far & the maven planets are aligned with openjpa, the next hurdle youhit is how do you run stuff in your IDE. If like me you use IDEA andmaven2, the project gets auto-created by default for all projects you workon.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 inyour project. Hooray, after a day or two's work, you can now actuallyuseopenjpa in your IDE and your build. YAY! The downside is that now whennavigating 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 mavenbuilds while developing code to avoid getting code completion/ compileerrors etc. (I prefer to keep in my IDE where possible).Compare this whole malarkey with hibernate. You add hibernate to yourpom, 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 actuallyrun & debug your code while still being able to actually navigate thesource. 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 themaven 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 thatshould really only be an optimisation); but please can we have some inefficient but usable reflection/cglib type approach so folks can easilyswitch from hibernate to openjpa (and stay there) without pulling outourhair & swearing too much - or sneaking back at the first opportunityto get an easy life?Please don't take this mail the wrong way - I truly want openjpa to be asuccess, its a great piece of software. Its just a bit too hard to use outof the box right now. I'd truly like it to be trivial to switch fromhibernate to openjpa and never have to go back.How hard is it to add a reflection/cglib type alternative to the upfrontbytecode generation (like hibernate does) to save us from the development-time pain? -- James ------- http://macstrac.blogspot.com/ -- View this message in context:http://www.nabble.com/the-pain-of-post-processing-bytecode-% 28another-beg-for-a-simple-reflection-cglib-alternative-like- hibernate%29-tf3770760.html#a10660986Sent from the open-jpa-dev mailing list archive at Nabble.com.--Patrick Linskey 202 669 5907Notice: This email message, together with any attachments, may contain information of BEA Systems, Inc., its subsidiaries and affiliated entities, that may be confidential, proprietary, copyrighted and/or legally privileged, and is intended solely for the use of the individual or entity named in this message. 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