org.hibernate.cache

This package defines APIs/SPIs and implementations for the Hibernate second-level cache.

The legacy (and now deprecated) approach to caching is defined by the {@link org.hibernate.cache.CacheProvider} and {@link org.hibernate.cache.Cache} interfaces as well as the {@link org.hibernate.cache.CacheConcurrencyStrategy} interface along with the various implementations of all these interfaces. In that scheme, a {@link org.hibernate.cache.CacheProvider} defined how to configure and perform lifecycle operations in regards to a particular underlying caching library; it also defined how to build {@link org.hibernate.cache.Cache} instances which in turn defined how to access the "regions" of the underlying cache instance. For entity and collection data cache regions, {@link org.hibernate.cache.CacheConcurrencyStrategy} wrapped access to those cache regions to apply transactional/concurrent access semantics.

The improved approach is based on {@link org.hibernate.cache.RegionFactory}, the various {@link org.hibernate.cache.Region} specializations and the two access strategies contracts ({@link org.hibernate.cache.access.EntityRegionAccessStrategy} and {@link org.hibernate.cache.access.CollectionRegionAccessStrategy}). The general approach here is that {@link org.hibernate.cache.RegionFactory} defined how to configure and perform lifecycle operations in regards to a particular underlying caching library (or libraries). {@link org.hibernate.cache.RegionFactory} also defines how to build specialized {@link org.hibernate.cache.Region} instances based on the type of data we will be storing in that given region. The fact that {@link org.hibernate.cache.RegionFactory} is asked to build specialized regions (as opposed to just general access) is the first improvement over the legacy scheme. The second improvement is the fact that the regions (well the ones like entity and collection regions that are responsible for storing {@link org.hibernate.cache.TransactionalDataRegion transactional} data) are asked to build their own access strategies (see {@link org.hibernate.cache.EntityRegion#buildAccessStrategy} and {@link org.hibernate.cache.CollectionRegion#buildAccessStrategy}).

EHCache uses a net.sf.ehcache.store.MemoryStore and a net.sf.ehcache.store.DiskStore . The net.sf.ehcache.store.DiskStore requires that both keys and values be java.io.Serializable . However the MemoryStore does not and in ehcache-1.2 nonSerializable Objects are permitted.

The optimisitic locking capabilities are only utilized for the entity cache regions.

Unlike the methods on the Cache interface, all the methods here will only ever be called from access scenarios where versioned data is actually a possiblity (i.e., entity data).

Implementors should define a constructor in one of two forms:

• MyRegionFactoryImpl( java.util.Properties )
• MyRegionFactoryImpl()