org.hibernate.cache.spi.access.package.html Maven / Gradle / Ivy
Defines contracts for transactional and concurrent access to cached
{@link org.hibernate.cache.spi.access.EntityRegionAccessStrategy entity} and
{@link org.hibernate.cache.spi.access.CollectionRegionAccessStrategy collection} data. Transactions pass in a
timestamp indicating transaction start time which is then used to protect against concurrent access (exactly how
that occurs is based on the actual access-strategy impl used). Two different implementation patterns are provided
for:
-
A transaction-aware cache implementation might be wrapped by a synchronous access strategy,
where updates to the cache are written to the cache inside the transaction.
-
A non-transaction-aware cache would be wrapped by an asynchronous access strategy, where items
are merely "soft locked" during the transaction and then updated during the "after transaction completion"
phase; the soft lock is not an actual lock on the database row - only upon the cached representation of the
item.
The asynchronous access strategies are: {@link org.hibernate.cache.spi.access.AccessType#READ_ONLY read-only},
{@link org.hibernate.cache.spi.access.AccessType#READ_WRITE read-write} and
{@link org.hibernate.cache.spi.access.AccessType#NONSTRICT_READ_WRITE nonstrict-read-write}. The only
synchronous access strategy is {@link org.hibernate.cache.spi.access.AccessType#TRANSACTIONAL transactional}.
Note that, for an asynchronous cache, cache invalidation must be a two step process (lock->unlock or
lock->afterUpdate), since this is the only way to guarantee consistency with the database for a nontransactional
cache implementation. For a synchronous cache, cache invalidation is a single step process (evict or update).
Hence, these contracts ({@link org.hibernate.cache.spi.access.EntityRegionAccessStrategy} and
{@link org.hibernate.cache.spi.access.CollectionRegionAccessStrategy}) define a three step process to cater for both
models (see the individual contracts for details).
Note that query result caching does not go through an access strategy; those caches are managed directly against
the underlying {@link org.hibernate.cache.spi.QueryResultsRegion}.