+1 to all the Matt mentions. I personally don't see the point in re-inventing the wheel. Besides, using an existing (and sound) persistence manager like OJB would give Geronimo good traction both in feature-set and time-to-market. Not to mention the opportunities that belonging to Apache family would bring (things that immedietely come to my mind are potential for more stronger interaction between the Geronimo JTS and OJB OTM).
If the Geronimo team still strongly believes in getting into the business of writing O/R mapping frameworks, atleast an abstraction is due there. Just so, the native persistence manager could be swapped for either OJB (or even Hibernate, Toplink, Cocobase or whatever). Also, an early exposure to this abstraction could let OJB team to fill the gap. Further, bringing in another persistence service within the apache family (Torque vs. OJB vs. Geronimo-persistence), makes me wonder where we are going. Thanks, Raghu. -----Original Message----- From: Matthew Baird [mailto:[EMAIL PROTECTED] Sent: Friday, August 08, 2003 12:16 PM To: OJB Developers List Cc: [EMAIL PROTECTED] Subject: RE: [persistence] Some thoughts regarding CMP and JDO If I'm reading this correctly: 1. Version 1.0 is going to try and support several back ends other than just RDBMS's (ie LDAP, XML, CICS) 2. You've already started to re-implement the persistence mechanisms. 3. Using the "front ends" of other Persistence frameworks equates to roughly supporting their general API's and probably more specifically their Query API's, however all real work will be done by the new persistence code on the back end. 4. You are open to integrating code/thoughts from several different persistence mechanisms into the Geronimo-specific implementation. Feel free to correct me if I'm wrong on this one. Based on those assumptions: 1. This is a pretty huge project with a rather large featureset. Supporting non-relational backend stores is a major PITA without bringing a lot of value. 2. Do we need yet another persistence framework? Most people reading this have been involved in building persistence frameworks in the past and understand the scope. Is there a solid reason for not choosing something that is out there and just using that? At the very least, it's a huge head start on the project which allows more time to be spent building aspects of the container that don't already exist. 3. Isn't one of the Jakarta criteria "Alignment with existing Apache subprojects."? 4. Perhaps there is some show-stopper in the OJB design that will not lend itself to being used as the persistence layer. Although it sounds like the designs are aligned. It really comes down to a build vs. buy, and in this case the price is $0.00 so it seems to be a no-brainer. Why not turn the proposal upside down: Use OJB as the default back-end persistence mechanism and lend your CMP 2.0 experience towards making OJB a better project as well? cheers, Matthew -----Original Message----- From: Dain Sundstrom [mailto:[EMAIL PROTECTED] Sent: Thu 8/7/2003 9:34 AM To: Mahler Thomas Cc: [EMAIL PROTECTED]; OJB Developers List (E-Mail) Subject: Re: [persistence] Some thoughts regarding CMP and JDO Hello Thomas (and the rest of the OJB team), Jeremy Boynes and I (and a few others) wrote the CMP 2.0 implementation in JBoss, and we have been working on the persistence code in the initial Geronimo code base. There is some code right now (a compiler and sql generator) and a fairly extensive design, but it looks like we have similar designs. The design is fairly simple from the high level. We will support several front end layers simultaneously at runtime (CMP, JDO, maybe Hibernate, heck maybe SQL). The job of the front end layer is to handle the life-cycle and callbacks required by the related specification, but all real work will be delegated to a centralized persistence service. This persistence service handles caching, locking, versioning, clustering and so on. When persistence service actually needs to manipulate data it delegates to a store manager service. The target initial store managers include SQL 92, SQL 99, Oracle (which is not really SQL), file based (XML maybe), and we have plans to add LDAP, clustered database layer and some legacy systems. The following ASCI picture sums this up (if it comes through): --------------- CMP ----------> | | ------> SQL JDP ----------> | persistence | ------> Oracle Hibernate ----> | manager | ------> LDAP | | ------> CICS (whatever) --------------- Now the persistence manager has a huge job, so it is broken down into plugins for caching, locking and so on, which effectively makes the persistence manager just a coordinator of the plugins. Anyway, this is getting a little too technical for right now, considering the initial code doesn't even have Entity beans. From what I have seen, we have a similar vision, and I think we should talk about merging our efforts into a common persistence engine (maybe we can even get Gavin and the Hibernate team to sync up with us). I think it would be really positive for Java to at least have all of us at least talking so our systems can play well together, but if we joined forces.... :D -dain On Thursday, August 7, 2003, at 07:02 AM, Mahler Thomas wrote: > Hello all, > > I'm contacting you on behalf of the Apache OJB development team > (http://db.apache.org/ojb). > OJB is part of the Apache DB subproject and aims at providing first > class > standards based object relational mapping technology. We are currently > finalizing our 1.0 release. > > Our team is excited to have a complete J2EE implementation at Apache > and we > are willing to contribute to your project. > > OJB is heavily used in Tomcat, JBOSS and other application server > environments and supports JTA and JCA. > OJB provides special support for implementing BMP solutions easily. > It provides ODMG and JDO compliant APIs. > > That's why we feel that OJB is a natural choice if you are thinking > about a > persistence engine to implement CMP (and maybe JDO). We are willing to > integrate all necessary changes into our codebase. > Who is working on persistence concepts? Whom could we contact to get > involved into the respective discussions? > If you have any questions don't hesitate to contact me or the ojb > developer > mailing list. > > cheers and all the best for this new project, > Thomas Mahler > > OJB developer > mailto:[EMAIL PROTECTED] --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
