I'm proposing to move the cacheable class configuration processing from the datacache classes to ClassMetaData. The feature, introduced in
OPENJPA-1045, effectively works by returning null for ClassMetaData.getDataCacheName(), where classes which should not be cached return null, otherwise the name of the datacache they may be cached by is returned.
THe problem is that some third party datacache plugins are not reentrant, and the existing ClassMetaData.isCacheable() makes use of the method call getRepository().getConfiguration().getDataCacheManagerInstance(). This invokes the initialization of the datacache, which may result in further initialization/copying of CMD objects, which reenter the isCacheable() method. If a third party datacache plugin is not reentrant safe, this can cause a failure in the form of Exceptions or hung threads.