Here's an idea on the collection restriction discussion. How about something
like this:
/**
* Interface implemented by classes which are used to create a custom
* query for the contents of a collection property, when the usual
* fk/pk approach is insufficient.
*/
interface org.apache.ojb.broker.query.QueryBuilder
/** Build the query to retrieve the specified collection property */
Query buildQuery(Object obj, ClassDescriptor cld, CollectionDescriptor cds);
}
class PersistenceBrokerImpl {
private void retrieveCollection(...) {
if (cds.getQueryBuilder() != null)
{
fkQuery = cds.getQueryBuilder.buildQuery(obj, cld, cls);
}
else if (cds.isMtoNRelation())
{
fkQuery = getMtoNQuery(obj, cld, cds);
}
else
{
fkQuery = getForeignKeyQuery(obj, cld, cds);
}
}
}
Then in my app I would write something like this:
class gov.doi.cap.ojb.query.BuildProjectsQuery implements QueryBuilder { ... }
<collection-descriptor
name="projects"
elementClass="gov.doi.cap.ojb.dataobjects.Project"
... >
<query class="gov.doi.cap.ojb.query.BuildProjectsQuery">
<attribute
attribute-name="earliestStart"
attribute-value="1999"
/>
<attribute
attribute-name="latestStart"
attribute-value="2001"
/>
</query>
</collection-descriptor>
This would allow great flexibility in the specification of the collection
contents, without requiring a query syntax to be defined in XML.
-steve
Steve Clark
Technology Applications Team
Natural Resources Research Center/USGS
[EMAIL PROTECTED]
(970)226-9291
>Date: Fri, 21 Feb 2003 17:49:32 +0100
>From: Jakob Braeuchi <[EMAIL PROTECTED]>
>To: OJB Users List <[EMAIL PROTECTED]>
>Subject: Re: 1:M querys constraints
>
>hi bill,
>
>what kind of restrictions woukd you need in the collection-descriptor ?
>do we need the full blown criteria there ?
>have you already any ideas about the definition of these restrictions ?
>
>i'm asking these questions because i do not want to parse restrictions
>in the collection-descriptor.
>i prefer a simpler solution like :
>
><restriction field="firstname" operation="=" value="Mark" />
><restriction field="lastname" operation="like" value="M%" />
>
>how could we handle 'AND' / 'OR' ?
>
>what do yout think about ?
>
>jakob
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