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  package org.apache.cayenne.cache;
  
  import org.apache.cayenne.query.QueryMetadata;
  
  import java.util.List;
  
  /**
   * Defines API of a cache that stores query results.
   *
   * @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("rawtypes")
      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.
       * <p>
       * 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("rawtypes")
      List get(QueryMetadata metadata, QueryCacheEntryFactory factory);
  
      @SuppressWarnings("rawtypes")
      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);
  
      /**
       * Removes a group of entries identified by group key.
       * Can be used if cache provider supports strictly typed caches.
       * @see QueryCache#removeGroup(String)
       *
       * @since 4.0
       */
      void removeGroup(String groupKey, Class<?> keyType, Class<?> valueType);
  
      /**
       * Clears all cache entries.
       *
       * @deprecated since 4.0. Please use implementation specific methods to perform cache management tasks.
       */
      @Deprecated
      void clear();
  }
  