how to use another implementation for JPA 2 level 2 cache?

We'd like to use another L开发者_开发百科2 cache for our big JPA application. We are trying to achieve a shared cache between multiple servers.

We use Eclipselink as JPA implementation, and some legacy codes uses internal Eclipselink API's, so switching is not an option.

Coherence/Toplink Grid seems too expensive (4000$/cpu?).

Is there a way we could plug another cache implementation? Is something specified in JPA 2 (I can't find anything in the specs, but maybe I just misread it)? Proprietary (=Eclipselink specific) solutions are ok, as long as they are somewhat documented or simple enough (we don't want that to break).

Is there a way we could plug another cache implementation?

Did you investigate the use of the EclipseLink shared object cache that comes with EclipseLink? Going by the description, the shared object cache is not confined to a single EntityManager alone, and is available across the lifecycles of several Entity managers, i.e. across several transactions. It is of course, constrained to the lifecycle of an EntityManagerFactory, which may be as live as long as the application is running in the container.

The EclipseLink shared object cache is different from Oracle Coherence, and I believe it is not licensed and packaged separately, thereby making it available on all containers.

JPA does not specify a pluggable cache interface. I don't know if it ever will, but if it does, my bet is that it won't be until after the resurrected JSR-107 finishes defining a standard API to object caches, which JPA would then be able to use. It might also have to wait for JSR 347, which is defining another cache interface, whose relationship to JCache is somewhat unclear (there is open factional warfare between and within the groups, with some members of the 107 expert group trying to declare 347 an independent republic, and invade Mexico).

So, until then, you're at the mercy of your provider's cache interface. I am not an EclipseLink expert, but last time i looked, i couldn't see a pluggable second-level cache interface. In fact, i think only Hibernate and, of course, DataNucleus, have them.

Most cache implementations are not distributed (other than Coherence), just local. EclipseLink already supports a share cache and cache coordination for caching in a cluster.

What cache do you intent to use, and what benefit do you intend to get from it?

EclipseLink does support integration with 3rd party caches, this API was created for the Coherence integration, although Coherence is the only cache that currently provides an integration.