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From David Jordan <davej...@bellsouth.net>
Subject Re: The Future of JDO
Date Thu, 05 Oct 2006 23:32:54 GMT

I am not at all opposed to what Andy has suggested. I guess the big  
question is whether JDO offers enough beyond JPA that makes this  
effort worthwhile, versus everyone just doing JPA.

On Oct 5, 2006, at 7:17 PM, Ilan Kirsh wrote:

> 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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