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From Jakob Braeuchi <jbraeu...@gmx.ch>
Subject Re: Query and QueryByCriteria
Date Fri, 25 Mar 2005 17:06:39 GMT
hi vadim,

query-refactoring is already on my todo-list. i prefer to convert 
QueryByCriteria into an interface and to have a QueryByCriteriaImpl class.


Vadim Gritsenko schrieb:
> Hi All,
> I would like to introduce new Query implementation, which is a 
> simplified version of the QueryByCriteria - it does not support 
> arbitrary criterias but only criterias with certain structure [1].
> While working on impementation, I noticed, that despite the fact that 
> there is base interface - Query - OJB relies in many parts on particular 
> class - QueryByCriteria. So for my query implementation I have several 
> ways of working this around:
>   * Extend my query class from QueryByCriteria and override some methods
>     to disable extra functionality. OJB internals will remain unchanged,
>     mostly, and will still rely on QueryByCriteria.
>   * Introduce base abstract class which replaces QueryByCriteria. OJB
>     internals can rely on this abstract class instead of concrete
>     QueryByCriteria class with lots of implementation details.
>   * Extend Query interface to incorporate methods introduced in
>     QueryByCriteria. OJB internals can rely on interface instead
>     of concrete class.
>   * Any other good approach which I missed?
> Now question, which way is the most appealing way to OJB developers? My 
> goal is to have these changes incorporated back into OJB, so I'd like to 
> take the approach which is preferred by OJB team.
> Another question I had is of more abstract nature... Why OJB's Query 
> implementations are not immutable objects? It does prevent caching of 
> Query obhects, multithreaded usage of Query objects, etc. To me, ideal 
> OJB architecture would rely on Query interface and treat Query instances 
> as immutable objects - so that new Query implementations can be plugged 
> in easily, and Query objects themselves can be passed on by reference 
> without any problems.
> [1] This new Query will implement query-by-primary-ley and 
> query-by-reference functionality - with support of plain SQL as well as 
> stored procedures. As a side effect, it will provide some 
> query-by-example-object functionality. Current 
> QueryFactory.newQuery(Object example) is confusing to me - it can not 
> really create a query by example object, only query by primary key, right?
> Thanks,
> Vadim
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