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From Ilan Kirsh <ki...@objectdb.com>
Subject Re: The Future of JDO
Date Thu, 05 Oct 2006 23:17:05 GMT
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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