For other persistence frameworks, I think we will be able to share and swap implementations of plugins or at least design ideas.
-dain
On Thursday, August 7, 2003, at 03:59 PM, Emmanuel Bernard wrote:
Hum, some Reply-To issue
Emmanuel Bernard wrote:
Hello Dain,
I'm not a persistence expert but I missed some stuffs. Its looks like the front end layer will delegate to the persistence manager and the persistence manager will use several plugins (one implementation out of n for each kind of plugin). What I missed is that Hibernate, for example, seems to be the persistence manager AND the plugins. I do not know how to keep the plug-in architecture and still use such persistence layers exept if Hibernate is hacked to conform to this architecture.
If I understand well, the architecture you propose is uniformisation of peristence layer (the same stuff Avalon try to do with component life-cycle). Am i right ?
Emmanuel
Dain Sundstrom wrote:
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]
/************************* * Dain Sundstrom * Partner * Core Developers Network *************************/
