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Re: [eclipselink-users] Coordinating the cache of different PersistenceUnits
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Oh yeah of course, ServerSession. Thanks again Gordon.
Cheers,
Steve
Gordon Yorke wrote:
Just two points. First the SessionCustomizer will be registered with
the ServerSession. The persistence unit property will take of that.
Second. The POJO's must continue to have the same properties in all of
the Persistence Units otherwise the cache co-ordination may fail.
--Gordon
Steve Sims wrote:
Hi Gordon,
Thank you very much for your help. I think you've cracked it for me,
what you're saying is:
1) I configure Cache Co-ordination for each ClientSession by
registering a SessionCustomizer which sets up the connection to, for
example, a single JMS topic "jms/singleCacheCoordination" (as
described in the links that you posted and here
http://wiki.eclipse.org/Configuring_a_JMS_Coordinated_Cache_(ELUG) )
2) There's no discrimination between entities updated by different
Persistence Units i.e. each entity has a global identity (which all
JPA entity POJO instances in all L2 caches, regardless of Persistence
Unit, can be identified with) and therefore wherever it's cached in an
L2 cache associated with a ClientSession that is subscribed to
"jms/singleCacheCoordination", it will be updated.
Many thanks again for your help,
Steve
Gordon Yorke wrote:
Cache Co-ordination will co-ordinate between different Persistence
Units if all Persistence Units are configured for co-ordination.
Information on configuring Cache-Cordination in EclipseLink can be
found here :
http://wiki.eclipse.org/Configuring_a_Coordinated_Cache_(ELUG) In JPA
you will need to use a SessionCustomizer (
http://wiki.eclipse.org/Customizing_the_EclipseLink_Application_(ELUG)#Using_the_Session_Customizer_Class
)and use the JAVA co-ordination configuration.
If you have any other questions feel free to ask.
--Gordon
Steve Sims wrote:
Hello,
I was wondering if somebody could help me with a question about the
relationship between different persistence units, their cache and
how to coordinate them. I'm sorry in advance if this post is a
little basic to post on this list, but I've read through the
EJB3-persistence spec (which correctly leaves implementation details
to the JPA provider) and the eclipselink-a-pedia and wiki which I
could follow a little but don't really know what I'm looking for!
Anyway, I have a core application that represents a number of
different businesses or "Service Providers" to which I'd like to add
specialised Service Provider applications after deployment such as
an application specifically for Restaurants or Taxis etc.
Not knowing too much about database design and architecture, I'm
thinking that the best way to architect it, from a software
perspective is composition; so the core data about a Service
Provider that's common to all providers (such as a phone number,
name, address etc.) would exist in a core Persistence Unit
("corePU") controlled by a core application with corresponding
business logic.
The more specific applications that would be deployed later, say for
example a Restaurant application, would have a Restaurant specific
Persistence Unit ("restPU") and business logic and would store
information about a Restaurant Service Provider that was specialised
such as menus or cost of a meal etc.
So my persistence units would "ideally" look like this:
corePU:
- ServiceProvider Table
- Phone Number
- Name
- Address
restPU:
- Restaurant Table
- ServiceProvider (OneToOne)
- Meal Cost
Unfortunately, because of the ServiceProvider reference, as I need
to run a JPQL query on a Restaurant such as "find all low cost
restaurants near to this address", I need to have the
ServiceProvider objects in the same Persistence Unit as the
Restaurant - but they're also in the the corePU. Just to make it
more difficult, I want to run this in a cluster too!
Therefore, my restaurant persistence units now look like this!
corePU:
- ServiceProvider Table
- Phone Number
- Name
- Address
restPU:
- ServiceProvider Table
- Phone Number
- Name
- Address
- Restaurant Table
- ServiceProvider (OneToOne)
- Meal Cost
So finally (and sorry about this huge post), I have JPA eclipselink
L2 cached objects floating around in "corePU" that I update through
the core app's business logic, however I need to see those changes
in "restPU"'s JPQL queries. Therefore, is there any way of getting
the L2 cache of "corePU" to synchronise with the L2 cache of
"restPU" or am I going to have to use the Database as my single
point and use EntityManager.flush() in the core app and the
QueryHint.REFRESH in restPU (which is what I'm currently doing but
it's presumably going to kill scalability)?
...or please feel free to tell me if I'm just being silly and
abusing PersistenceUnits?
Many thanks in advance for getting to the end of this post!
Steve
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