org.apache.cayenne.cache.QueryCache Maven / Gradle / Ivy
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package org.apache.cayenne.cache;
import java.util.List;
import org.apache.cayenne.query.QueryMetadata;
/**
* An interface that defines generic QueryCache.
*
* Note that depending on implementation, {@link #remove(String)},
* {@link #removeGroup(String)} and {@link #clear()} methods may mark the matching
* existing entries as expired instead of actually removing them. So it may appear that
* the size of the cache, as reported by {@link #size()} method, is unchanged.
*
* @since 3.0
*/
public interface QueryCache {
/**
* Returns a cached query result for the given QueryMetadata or null if the result is
* not cached or is expired.
*/
@SuppressWarnings("unchecked")
List get(QueryMetadata metadata);
/**
* Returns a cached query result for the given QueryMetadata. If the result is not
* cached or is expired, cache will use provided factory to rebuild the value and
* store it in the cache. A corollary is that this method never returns null.
*
* Compared to {@link #get(QueryMetadata)}, this method allows the cache to do
* appropriate synchronization when refreshing the entry, preventing multiple threads
* from running the same query when a missing entry is requested by multiple threads
* simultaneously.
*/
@SuppressWarnings("unchecked")
List get(QueryMetadata metadata, QueryCacheEntryFactory factory);
@SuppressWarnings("unchecked")
void put(QueryMetadata metadata, List results);
/**
* Removes a single entry from cache.
*/
void remove(String key);
/**
* Removes a group of entries identified by group key. Note that depending on
* implementation this method may either actively remove the entries belonging to the
* group or just mark them as expired, so that they are refreshed on the next access.
* In the former case the cache size would shrink, but in the later the cache size
* will not change after calling this method.
*/
void removeGroup(String groupKey);
/**
* Clears all cache entries.
*/
void clear();
/**
* Returns the number of entries currently in the cache, including expired but not
* removed entries.
*/
int size();
}