AW: [Objectbridge-jdo-dev] Non-JDBC data sources

[Mahler T. <tho...@it...>]

Hi David,

> -----Urspr=FCngliche Nachricht-----
> Von: David Zejda [mailto:dv...@at...]
> Gesendet: Donnerstag, 13. Juni 2002 01:17
> An: Obj...@li...
> Betreff: [Objectbridge-jdo-dev] Non-JDBC data sources
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> I know, that OJB's focus sharpness (faq: It's concerned with=20
> O/R mapping and
> nothing else.) is design/manage advantage, but I work on=20
> project, where it's
> crucial to integrate disparate data sources (RDBMS, ODBMS,=20
> XML based DBMS,
> flat-files, vendor specific formats..). I decided not to use closed,
> non-free solutions at all, so OJB (open-source, clearly designed,
> scalable...), seems to be suitable as a persistency-heart.
> Could you advise how to get on with OJB?


> 1) use OJB as a single persistency adaptor, manage several ODMG
> implementations, make some fascade to hide it, e.g. solve distributed
> transactions...?

If there are existing ODMG Java bindings to you other datasources this =
will
be vers easy.
Just write litte wrappers that route user request to different ODMG
implementations.

If there is no ODMG API for a given persistent store, you can implement =
a
dedicated PersistenceBroker for this special persistent store.
This way you can use the OJB ODMG (or JDO if you prefer) implementation =
to
access arbitrary persistent stores.

> 2) extent OJB (add persistency adpators to OJB) - if=20
> publically useful,
> release them under LGPL as modular OJB's parts/add-ons?

Yes, that's what I'm recommending. have a look at our persistence =
kernel
interface ojb.broker.PersistenceBroker.
It contains no specifics for RDBMS. It is a generic abstractiion of an
object store.
There could be implementations for OODBMS, RDBMS, XML databases, file =
system
or Directory Services !=20

You only have to provide a persistent store specific PersistenceBroker
Implementation.
Than you can use the OJB ODMG or JDO layer to work against those =
specific
brokers.

regarding OJB scope:
As OJB will be one of the foundation projects of the new db.apache.org =
site,
our scope is not longer limited as mentioned in the faq.
OJB will be a generic object persistence integration platform!

Thus having new PersistenceBroker implementations is very interesting =
for
us!
(especially XML, OODBMS, LDAP, flat-file)

As we are moving to Jakarta, we will use the apache licence soon.

> 2.1) is this posible without (negative) impact on OJB's actual design

yes no problems!=20

> 3) something else?
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> In the roadmap there is (4me) a bit mysterious  sentence "provide
> distributed Meta-Object Protocol access through PersistenceBroker =
API"

This has been implemented a long time ago. OJB comes with a =
client/server
mode. To have fully operational clients it is necessary to have =
meta-data on
the client too. This was not possible in the early days, but now it is.

> Somewhere in OJB doc I read about possibility to build my own
> PersistenceManager. Does it relate to mentioned problem?
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No. You simply have to implement the PersistenceBroker interface to =
write a
new storage adaptor.

A persistenceManager would be something like your own ODMG or JDO
implementation. That would be a much more difficult task!

cheers,

Thomas

> Thanks for reply
> David Zejda
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>=20
> PS: I know, I can suck all wanted info from API, but I thing, you =
(OJB
> experts) can answer quickly and painlessly.
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> BTW thanks for OJB, well done!
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> _______________________________________________________________
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> August 25-28 in Las Vegas -=20
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