+1 for extensible entity mappings.
When registering a new mapping, i think that it should be possible to
specify if it should apply to a particular wiki or to the whole farm.
The collection of mappings for the whole farm should of course be
enabled for new wiki instances.
While we are at it, we should try to find a better way to implement
virtual wikis. As I've already mentioned, I believe that this can be
achieved by reregistering entity mappings per wiki, with prefixed entity
names. (This would really be the same as extensible entity mappings.)
It seems that this should enable access to multiple wikis within the
same Hibernate session, while being fully backwards compatible with the
current implementation.
But Denise wrote "[...] I doubt you will reach soon a state where
hibernate support sessions across databases." and I'm not sure if he
knows something about Hibernate limitations that would prevent this
solution.
The XML-schema for entity mappings allows for both a schema and catalog
attributes to the class element. If this is implemented in the expected
way, it should work to use mapping templates such as:
<class name="${entityNamePrefix}:com.xpn.xwiki.doc.XWikiDocument"
table="xwikidoc" schema="${entitySchemaAttribute}">
and for MySQL
<class name="${entityNamePrefix}:com.xpn.xwiki.doc.XWikiDocument"
table="xwikidoc" catalog="${entityCatalogAttribute}">
And then you implement an EntityNamingStrategy for selecting the correct
mappings for the current wiki.
Best Regards,
/Andreas
2012-10-02 20:53, Vincent Massol skrev:
> Hi devs,
>
> I'd like to propose the following to implement
> http://jira.xwiki.org/browse/XWIKI-8271:
>
> * Create a new xwiki-platform-store-hibernate module
> * Add a Component role: HibernateConfiguration implements Comparable
> * API: void HibernateConfiguration.configure(Configuration
> aggregatedConfiguration), where the passed aggregatedConfiguration contains
> the configuration filled by all the HibernateConfiguration.configure() calls
> executed before
> * Add a HibernateConfigurationManager.getConfiguration() component that is in
> charge of loading the various HibernateConfiguration in the correct order
> * Have an AbstractHibernateConfiguration implements HibernateConfiguration
> with 1 API: getDatabaseType(Configuration configuration). It gets the DB type
> from the connection URL string and returns a DatabaseType object which
> represents the database type
>
> * CoreHibernateMapping (hint = "xwiki") <==> xwiki.hbm.*.xml - highest
> priority, defines the connection URL among other props
> * ActivityStreamHibernateMapping (hint = "activitystream")
> * FeedHibernateMapping (hint = "feeds")
>
> Note 1: If a HibernateConfiguration impl needs to load mappings that depend
> on the DB they call AbstractHibernateConfiguration. getDatabaseType() to get
> the DB.
> Note 2: If the user wants to use a different HBM file, he/she just has to put
> a file with the same name (e.g. xwiki.hbm.xml) in WEB-INF/classes
> Note 3: This means we won't put any mapping anymore in the hibernate.cfg.xml
> file since it's not needed anymore (although it would continue to work if you
> put mappings there).
>
> Usage:
>
> @Inject
> HibernateConfigurationManager configurationManager;
>
> Configuration configuration = configurationManager.getConfiguration();
> SessionFactory sessionFactory = configuration.buildSessionFactory();
>
> Then all that remains to implement http://jira.xwiki.org/browse/XWIKI-8271 is
> to have a component singleton that will be in charge of returning the
> SessionFactory and which can be asked to rebuild a new SessionFactory (using
> a new Configuration).
>
> We'll just need to decide how we trigger this. 2 options:
> * By using an Event Listener listening on HibernateConfiguration
> registrations and recreating automatically a new SessionFactory when it
> happens. Cons: if an extension contributes several HibernateConfiguration
> then Hibernate will be reinitialized several times
> * By listening to an Event sent by the Extension Manager when an extension
> has finished loading and somehow find out all the HibernateConfiguration that
> have been added (several ways of doing this) and recreating the SessionFactory
>
> Note: The only issue I can foresee is if a Hibernate call is in progress in
> one thread when an extension is installed and a new SessionFactory is created
> at the same time. Either we don't care or we could implement retry at the DB
> level, or we could introduce some semaphore so that we start the reinit only
> when nobody has a lock on the SessionFactory, or…
>
> WDYT?
>
> Of course, the pros is those listed in
> http://jira.xwiki.org/browse/XWIKI-8271:
> * Ability for a platform module to contribute Hibernate mappings (static)
> * Ability for an extension installed at runtime to contribute Hibernate
> mappings (dynamic)
>
> Note that the reason I'm starting all this is because I'd like to implement
> http://jira.xwiki.org/jira/browse/XWIKI-7953 cleanly in a module separate
> from oldcore.
>
> Thanks
> -Vincent
>
> _______________________________________________
> devs mailing list
> [email protected]
> http://lists.xwiki.org/mailman/listinfo/devs
>
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