Re: [rc5 / bug / MetadataManager] Memory leak using dynamic mappi ng on per thread bases [ why we need a frech copy!!!]

[Armin Waibel <ar...@code-au-lait.de>]

Hi Roger,

Janssen, Roger wrote:
...
>>Why you need a 'fresh'copy for each thread/call? Could be a performance 
>>problem - maybe I misinterpret your needs.
> 
> 
> for every persistence operation (query/store/delete/etc...) we instantiate a
> new persistence broker, to my knowledgde, this is supposed to be common
> practice.

right, get instance from pool for each action and close (return to pool) 
after use.

> in our webapp we inplemented a relation service that manages
> relations between objects. a relation is of a certain relationtype has
> references to the related objects, these references are by object id.
> relations can be of many different types, and thus may have references to
> many different types of objects. we may query our objects on attributes of
> related objects, so every Linkable (a marker interface) object implements a
> collection links/relations, which contains a collection of related objects.
> it is not scalable to implement a new collection for every new relation
> type, or for every new linkable target object class. we are going to have
> many of these, it just is not managable (in java-classes, in O/R
> repositories etc.). So each Linkable class implements one links/relations
> collection, which has a 'dummy' mapping in the  O/R repository file.
> Runtime, dynamically, this mapping is modified and set to the correct
> references, because for instance when issuing a query, we know what class
> and link references to use. This may change for every query!
> 
> So this is why we copy the repository every time.
> 
> Hope this gives you some insight in how we use this feature.
> 
wow, incredible! Does this mean that users can change/manipulate 
relations of objects at runtime?

As your case of metadata manipulation is exceptionally, do you have any 
special wishes/proposals/suggestions for improvement for OJB 1.1?
Some ideas are:
- Make MetadataManager pluggable (but I don't know if we can guarantee a 
stable interface at this time, maybe some method will change in further 
versions)

- Allow metadata manipulation of current used PB instance at PB 
"lifetime" (after request from pool, before return to pool) by using 
PB.setDescriptorRepository(...) method (Currently we have some direct 
dependency to MetadataManager in ObjectFactory and QueryByCriteria, thus 
they wouldn't notified when metadata of current used descriptor change).

regards,
Armin

> thanx again,
> 
> Roger Janssen
> 
> 
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