You can get some benefit from named queries in terms of query pre- compilation and caching on the underlying database. However, most database flavors and hibernate providers turn criteria queries into named queries (parameterized SQL) which is then cached, so, on the surface I suspect the performance characteristics will be similar.


On 18-Jan-08, at 14:35 , Rahul Thakur wrote:

Thanks Emmanuel! Responses inlined...

Emmanuel Venisse wrote:
Hi Rahul,

After few days to look at JPA, I'm sure now it would be good to use it
instead of the actual JDO/JPOX (I know JPOX 1.2 support JPA).
The code is very easy to write and to read with JPA.

About your continuum-jpa branch, I have few remarks:
- I don't think it's good to use directly some OpenJPA APIs. If possible, I'd prefer to use only standard JPA APIs so we'll can choose later the
implementation we want to use (OpenJPA, TopLink, JPOX...)

Agree. The only place where OpenJPA APIs are being used directly currently are the unit tests.
- why do you use some Spring code?

Experimental. Spring has a good transaction management framework out of the box.
- we don't need to store the model encoding (CommonUpdatableModelEntity

Sure. Easily fix'able. :-)
- can you explain dateCreated/dateUpdated fields? How are they managed?

These are for audit puposes, and can be used as range search query criteria for fetching entities. These were an extension I thought will be good. 'dateCreated' gets set when an entity is first inserted into the underlying store, subsequent updates update the 'dateUpdated'.
- all the model is fectched eagerly and it isn't acceptable for performance

Yes, the model does needs review and tweaks to annotations where we know we don't need to fetch 'eagerly'.
- I'm not sure your Query "pattern" is good. I'd prefer to use named queries
but maybe you have a reason

I think using a Query like we have on the JPA branch nicely provides for a flexible construction of queries (i.e, only the criteria passed in contributes to the query). I am not sure if such is available with named queries; but I am interested to know why named queries might be better.


That's all for the moment.


On Jan 16, 2008 11:30 PM, Rahul Thakur <[EMAIL PROTECTED]> wrote:

Just wondering if anyone else got to the changes?

Emmanuel Venisse wrote:

I don't have the time to look at it these days but I'll do it asap
(maybe in few weeks :( )


Rahul Thakur a écrit :

Hi All,

Scribbling some quick notes on some of the toying around I have been
doing with OpenJPA, Generics etc on the continuum-jpa branch[1]:

1) Use JPA for persistence
Motivation behind this has been to investigate how this compares to
JPOX/JDO for managing the model - both in terms on performance and
ease of use (Store APIs). Continuum model classes are annotated with JPA annotations on the branch. However, this needs a review as there are some elements (for example 'configuration' typed as Map) that I am
not sure yet how to persist yet. The provider used is OpenJPA [2].

2) Refactorings to Store interface
Main motivation has been to keep the core Store interface lean and
mean (read extensible). The Store interface[3] now has 4 methods:

The lookup(), save() and delete() act on single model Entity, while query() will filter and obtain matching Entities from the underlying database based on the Query specified. Query implementations control how a resulting JPQL gets constructed and which matching entities get
pulled, and can be easily extended.

To preserve compatibility with the existing Store interface, we can mimick the existing ContinuumStore interface operations by having a
facade that can prepare requisite queries and delegate to a Store

3) Misc.
There are a few I am investigating:
1) Spring/Guice under the hood.
2) JUnit 4.4 (and Hamcrest library)
, but these are still in early stages.

I am keen to get a feedback on what others think.



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[2] -

[3] -

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