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*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
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*/
package org.apache.openjpa.kernel;
import java.util.List;
import java.util.Map;
import org.apache.openjpa.lib.conf.Configurable;
/**
* A cache to create and maintain {@link FinderQuery finder queries}.
*
* A finder query is a query to find instance of a given class by its primary
* identity. This cache maintains finder queries by generic identifier of
* parameterized type K.
*
* A cached query by an identifier of parameterized type K.
*
* A query can be cached by an identifier and value represented by parameterized
* type V. Caching results in creating a new instance of FinderQuery FQ from the
* value V such that FQ can be executed to return a result of parameterized type
* R. A request to cache may not be successful if this cache determines the
* value V to be not cachable.
*
* Both get() and put() operations can be controlled by the hints associated
* with FetchConfiguration.
*
* The target database query FQ associated to a cached finder query F
* may depend upon query execution context such as fetch plan or
* lock group. This cache, by design, does not monitor the context or
* automatically invalidate an entry when the original query F is executed
* with context parameters that affect the target query FQ.
*
* The user must notify this receiver to invalidate a cached entry when
* execution context changes in a way that will modify the resultant database
* language query FQ.
*
* One of the built-in mechanism (available in JPA facade) is to set query hints
* to either invalidate the query entirely or ignore the cached version for the
* current execution.
*
* @see QueryHints#HINT_IGNORE_FINDER
* @see QueryHints#HINT_INVALIDATE_FINDER
* @see QueryHints#HINT_RECACHE_FINDER
*
* This cache allows customization of whether a query can be cached or not
* via either explicit marking of certain classes as non-cachable (which is
* irreversible) or addition/removal of exclusion patterns (which is reversible)
*
* @author Pinaki Poddar
*
* @since 2.0.0
*/
public interface FinderCache extends Configurable {
/**
* Get the FinderQuery for the given key.
*
* @param key for which the finder is looked up
* @param fecth may contain hints to control lookup operation
*
* @return FinderQuery for the given mapping.
*/
FinderQuery get(K key, FetchConfiguration fetch);
/**
* Cache a FinderQuery for the given key and value.
*
* @param key for which the finder is cached.
* @param value used to construct the finder query
* @param fetch may contain hints to control cache operation.
*
* @return the finder query that has been cached. It may be newly
* constructed or an existing query. If the given key-value can not be
* cached, then return null.
*/
FinderQuery cache(K key, V value, FetchConfiguration fetch);
/**
* Get a map view of the cached entries as strings.
*/
Map getMapView();
/**
* Remove the FinderQuery for the given key from this cache.
*/
boolean invalidate(K key);
/**
* Marks the given key as not amenable to caching.
* Explicit marking helps to avoid repeated computational cost of
* determining whether finder for a key can be cached or not.
*
* Explicit marking can not be reversed by removal of exclusion patterns.
*
* @return finder query for the given class if it had been cached before.
* null otherwise.
*/
FinderQuery markUncachable(K key);
/**
* Affirms if the given key matches any of the exclusion patterns.
*/
boolean isExcluded(K key);
/**
* Gets the excluded stringified keys.
*/
List getExcludes();
/**
* Adds the given pattern to the list of excluded patterns. Any existing
* cache entry whose key matches the given pattern will be marked
* non-cachable in a reversible manner.
*/
void addExclusionPattern(String pattern);
/**
* Removes the given pattern from the list of excluded patterns.
* Any excluded entry that matches the given pattern can now be cached
* again, unless it has been marked non-cachable explicitly.
*/
void removeExclusionPattern(String pattern);
/**
* Gets the simple statistics for executed finder queries.
*/
QueryStatistics getStatistics();
}