Package org.hibernate.cache.access

package org.hibernate.cache.access

Defines contracts for transactional and concurrent access to cached entity and 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:
invalid reference 
read-only
,
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read-write
and
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nonstrict-read-write
. The only synchronous access strategy is
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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 (

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org.hibernate.cache.access.EntityRegionAcessStrategy
and 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 QueryResultsRegion.