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//$Id: CacheConcurrencyStrategy.java 5685 2005-02-12 07:19:50Z steveebersole $
package org.hibernate.cache;
import java.util.Comparator;
/**
* Implementors manage transactional access to cached data. Transactions
* pass in a timestamp indicating transaction start time. Two different
* implementation patterns are provided for. A transaction-aware cache
* implementation might be wrapped by a "synchronous" concurrency 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"
* concurrency 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.<br>
* <br>
* For the client, update lifecycles are: lock->evict->release,
* lock->update->afterUpdate, insert->afterInsert.<br>
* <br>
* Note that, for an asynchronous cache, cache invalidation must be a two
* step process (lock->release, or lock-afterUpdate), since this is the only
* way to guarantee consistency with the database for a nontransaction cache
* implementation. For a synchronous cache, cache invalidation is a single
* step process (evict, or update). Hence, this interface defines a three
* step process, to cater for both models.
*/
public interface CacheConcurrencyStrategy {
/**
* Attempt to retrieve an object from the cache.
* @param key
* @param txTimestamp a timestamp prior to the transaction start time
* @return the cached object or <tt>null</tt>
* @throws CacheException
*/
public Object get(Object key, long txTimestamp) throws CacheException;
/**
* Attempt to cache an object, after loading from the database.
* @param key
* @param value
* @param txTimestamp a timestamp prior to the transaction start time
* @param version the item version number
* @param versionComparator a comparator used to compare version numbers
* @param minimalPut indicates that the cache should avoid a put is the item is already cached
* @return <tt>true</tt> if the object was successfully cached
* @throws CacheException
*/
public boolean put(
Object key,
Object value,
long txTimestamp,
Object version,
Comparator versionComparator,
boolean minimalPut)
throws CacheException;
/**
* We are going to attempt to update/delete the keyed object. This
* method is used by "asynchronous" concurrency strategies. The
* returned object must be passed back to release(), to release the
* lock. Concurrency strategies which do not support client-visible
* locks may silently return null.
* @param key
* @param version
* @throws CacheException
*/
public SoftLock lock(Object key, Object version) throws CacheException;
/**
* Called after an item has become stale (before the transaction completes).
* This method is used by "synchronous" concurrency strategies.
*/
public void evict(Object key) throws CacheException;
/**
* Called after an item has been updated (before the transaction completes),
* instead of calling evict().
* This method is used by "synchronous" concurrency strategies.
*/
public boolean update(Object key, Object value) throws CacheException;
/**
* Called after an item has been inserted (before the transaction completes),
* instead of calling evict().
* This method is used by "synchronous" concurrency strategies.
*/
public boolean insert(Object key, Object value) throws CacheException;
/**
* Called when we have finished the attempted update/delete (which may or
* may not have been successful), after transaction completion.
* This method is used by "asynchronous" concurrency strategies.
* @param key
* @throws CacheException
*/
public void release(Object key, SoftLock lock) throws CacheException;
/**
* Called after an item has been updated (after the transaction completes),
* instead of calling release().
* This method is used by "asynchronous" concurrency strategies.
*/
public boolean afterUpdate(Object key, Object value, Object version, SoftLock lock)
throws CacheException;
/**
* Called after an item has been inserted (after the transaction completes),
* instead of calling release().
* This method is used by "asynchronous" concurrency strategies.
*/
public boolean afterInsert(Object key, Object value, Object version)
throws CacheException;
/**
* Evict an item from the cache immediately (without regard for transaction
* isolation).
* @param key
* @throws CacheException
*/
public void remove(Object key) throws CacheException;
/**
* Evict all items from the cache immediately.
* @throws CacheException
*/
public void clear() throws CacheException;
/**
* Clean up all resources.
*/
public void destroy();
/**
* Set the underlying cache implementation.
* @param cache
*/
public void setCache(Cache cache);
/**
* Marker interface, denoting a client-visible "soft lock"
* on a cached item.
* @author Gavin King
*/
public static interface SoftLock {}
/**
* Get the cache region name
*/
public String getRegionName();
/**
* Get the wrapped cache implementation
*/
public Cache getCache();
}
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