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From Niall Gallagher <ni...@switchfire.com>
Subject JCS as a Hibernate cache provider
Date Fri, 22 Jun 2007 18:14:38 GMT
Hi All,

What is the state of play on using JCS as a Hibernate distributed
second-level cache? Is it possible to configure this?

I note on the Hibernate website that there is some out-of-date
documentation on configuring JCS as a cache provider in Hibernate 2.
Since then it seems JCS has fallen out of favour with Hibernate
developers. I don't see why. There does not seem to be an alternative
cache provider for Hibernate, which provides distributed cache
functionality like JCS does. Apart from Coherence, which seems extremely
expensive.

There are several distinct subsystems within this company -
inbound/outbound message interfaces (A), message processing systems (B),
web servers (C). We have common code which is shared between all systems
- user account objects, lookup data objects etc. Each subsystem also has
its own subsystem-specific set of objects however.

We want a distributed cache to allow subsystem C to access user account
and lookup data objects added to the cache by subsystem A. We do not
want subsystem C to receive replicated cache data for objects only
needed by subsystem A however. Thus we can't just configure every
subsystem on our network to be in the same cluster, as it would flood
our network with pointless traffic. We need to segment our data so data
stored in some cache regions is propagated or accessible only to
specific subsystems, but data stored in other cache regions is
accessible to all systems company-wide. JCS supports this sort of
configuration and it's why we are using it.

The apparent downside to JCS however, is that it's not documented as
capable of being configured as a Hibernate 3.2 second level cache, and
we load most of our data from databases using Hibernate. To store
Hibernate objects in the JCS cache, we are having to avoid defining the
relationships between our Hibernate persistent classes (i.e. specify the
relationships between the DB tables they represent) so that at runtime
when we try to put a persistent object in the JCS cache, it does not
'pull' the referenced objects with it.

If JCS was supported as a Hibernate second-level cache directly,
Hibernate would take care of this "object reference problem"
automatically, as it does for the other caches it supports directly.

Basically, we need the power of JCS as a distributed cache, because none
of Hibernate's other caches are powerful enough, but it would simplify
things for us a great deal if we could just configure Hibernate to use
JCS as a second-level cache.

Has anyone tried this?

We are using Hibernate 3.2 with Hibernate-annotations for accessing the
DBs. We have written some "JCS annotations" which we use to configure
JCS regions on-the-fly using a JCS wrapper interface we have written.
This allows us to specify the type of JCS caching we want per-class
using annotations (e.g. lateral/clustered vs. company-wide distributed).

Any information on JCS + Hibernate would be appreciated.

Kind regards,

Niall

____________________________________
Niall Gallagher
                
Senior Developer / Architect 
Switchfire Ltd. 
phone: 
              + 44 (0)20 7798 2807  
fax: 
              + 44 (0)20 7798 2801  
email: 
               niall@switchfire.com 
web: 
                 www.switchfire.com 


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