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From Ilan Kirsh <ki...@objectdb.com>
Subject Re: The Future of JDO
Date Fri, 06 Oct 2006 15:03:13 GMT
Hi Eric,

No doubt that currently most people are using Hibernate and using its old
API. A visit in Hibernate forums can also confirm this (compare the traffic
in the main forum to the traffic in the EJB3 forum). However, this might be
because JPA is still young and many people are working on existing systems.
An happy user do not look for changes. Therefore, the results of your survey
also make sense. I also feel that current ObjectDB users are happy with the
JDO API and will not switch to anything else.

However, we should try to look what happens in new projects. If I had to
start a new project using Hibernate, I would probably be using the JPA API
(where possible) to remain unlocked to Hibernate. Many people take this
exact decision these days. This is today when there are 3 JPA
implementations. I believe that in a short time (1-2 years) there may be
8-10 JPA implementations and then such a decision will be almost a must.

You write that you see a real value in going in this direction. I agree that
the real value is more regarding developers that do not use JDO today (which
unfortunately are the majority) rather than regarding  the current JDO
users.

Regards,

Ilan

----- Original Message ----- 
From: "Eric Samson" <eric.samson@xcalia.com>
To: "Ilan Kirsh" <kirsh@objectdb.com>; "Andy Jefferson" <andy@jpox.org>;
<jdo-dev@db.apache.org>; "JDO Expert Group" <jdo-experts-ext@sun.com>
Sent: Friday, October 06, 2006 4:25 PM
Subject: RE: The Future of JDO


Hi all

When I talk to prospects, customers, journalists, etc. I always introduce
JPA as a subset of JDO, which is true in terms of concepts.
I think there is a real value in aligning JDO on JPA where possible
(annotations, APIs, etc.) or at least in making JPA features as optional in
JDO (QL).

I agree with David when he says that JPA is not so popular and most people
still use raw proprietary Hibernate.

We recently ran a survey among our users: most of them don't even require us
to support JPA, and they won't move to JPA when will support it. They are
simply happy with JDO and want us to continue to support it.

Best Regards,
....: Eric Samson, Founder & CTO, Xcalia
Service your Data!

-----Message d'origine-----
De : Ilan Kirsh [mailto:kirsh@objectdb.com]
Envoyé : vendredi 6 octobre 2006 01:17
À : Andy Jefferson; jdo-dev@db.apache.org; JDO Expert Group
Objet : Re: The Future of JDO

My personal feeling after reading the JPA spec and two books on
EJB 3 / JPA is that JPA is not so weak. It has an excellent query
language and API that  is very similar to JDO (but more compact).
I highly recommend reading "Pro EJB 3 - Java Persistence API" /
Apress (despite statements such as "as a result JDO spent most of
its time in the persistence underground" and "the writing was on the
wall for JDO" - which are very natural for the two authors that work
for Oracle).

Anyway, I do think that JPA has good chances to succeed. It does
take time to achieve a critical mass of implementations and users but
it seems that JPA is on the right track. If it succeeds we should be
ready. Therefore, I think that Andy's list looks very good as a base
for JDO 2.1.

Ilan

> Totally agree. I would think of the following items
>
> 1. "persistence.xml". I see no real reason not to allow specification of
> classes to be persisted using persistence.xml as an additional way of
> creating the PMF.
>
> 2. Persistence API. There are not many differences between JPA and JDO
> methods
> so what you propose should be straightforward. Those JDO implementations
> that
> have/are implementing JPA will know that it is simply putting a wrapper
> around their existing JDO method. Why not include in 2.1?
>
> 3. Query Language. JPQL can be made available via the query "language"
> flag in
> the existing API (so we add "javax.jdo.query.JPQL" or something as a valid
> value). OK the JDO implementation (if supporting this language) will have
> to
> add a new query language but the hook is there. Could be an optional
> feature
> in JDO 2.1 ?
>
> 4. Types. Mandate support for Enums, Calendar when running under Java5, so
> all
> types that JPA supports are there. Why not include in 2.1?
>
> 5. Annotations. The donated JDO2 annotations need splitting between
> persistence annotations, and ORM. Looking through the JPA annotations some
> time ago, it wasn't clear that we can just take theirs and add others due
> to
> too many missing concepts. What the JDO(3) spec could do is firstly define
> the precedence of annotations and metadata (to match the JPA spec
> definition), and secondly define how JPA annotations can be used by a JDO3
> implementation. In addition provide JDO2/3 annotations to allow finer
> definition.
>
> -- 
> Andy




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