/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
 * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
 */
package org.hibernate.loader.collection;

import java.io.Serializable;

import org.hibernate.HibernateException;
import org.hibernate.MappingException;
import org.hibernate.engine.spi.LoadQueryInfluencers;
import org.hibernate.engine.spi.SessionFactoryImplementor;
import org.hibernate.engine.spi.SharedSessionContractImplementor;
import org.hibernate.internal.util.collections.ArrayHelper;
import org.hibernate.loader.Loader;
import org.hibernate.persister.collection.QueryableCollection;

A batch-fetch capable CollectionInitializer that performs batch-fetching using the padded style. See BatchFetchStyle for a discussion of the different styles.
Author:Steve Ebersole
See Also:
/** * A batch-fetch capable CollectionInitializer that performs batch-fetching using the padded style. See * {@link org.hibernate.loader.BatchFetchStyle} for a discussion of the different styles. * * @author Steve Ebersole * * @see org.hibernate.loader.BatchFetchStyle#PADDED */
public class PaddedBatchingCollectionInitializerBuilder extends BatchingCollectionInitializerBuilder { public static final PaddedBatchingCollectionInitializerBuilder INSTANCE = new PaddedBatchingCollectionInitializerBuilder(); @Override public CollectionInitializer createRealBatchingCollectionInitializer( QueryableCollection persister, int maxBatchSize, SessionFactoryImplementor factory, LoadQueryInfluencers loadQueryInfluencers) throws MappingException { int[] batchSizes = ArrayHelper.getBatchSizes( maxBatchSize ); Loader[] loaders = new Loader[ batchSizes.length ]; for ( int i = 0; i < batchSizes.length; i++ ) { loaders[i] = new BasicCollectionLoader( persister, batchSizes[i], factory, loadQueryInfluencers ); } return new PaddedBatchingCollectionInitializer( persister, batchSizes, loaders ); } @Override public CollectionInitializer createRealBatchingOneToManyInitializer( QueryableCollection persister, int maxBatchSize, SessionFactoryImplementor factory, LoadQueryInfluencers loadQueryInfluencers) throws MappingException { final int[] batchSizes = ArrayHelper.getBatchSizes( maxBatchSize ); final Loader[] loaders = new Loader[ batchSizes.length ]; for ( int i = 0; i < batchSizes.length; i++ ) { loaders[i] = new OneToManyLoader( persister, batchSizes[i], factory, loadQueryInfluencers ); } return new PaddedBatchingCollectionInitializer( persister, batchSizes, loaders ); } private static class PaddedBatchingCollectionInitializer extends BatchingCollectionInitializer { private final int[] batchSizes; private final Loader[] loaders; public PaddedBatchingCollectionInitializer(QueryableCollection persister, int[] batchSizes, Loader[] loaders) { super( persister ); this.batchSizes = batchSizes; this.loaders = loaders; } @Override public void initialize(Serializable id, SharedSessionContractImplementor session) throws HibernateException { final Serializable[] batch = session.getPersistenceContext() .getBatchFetchQueue() .getCollectionBatch( collectionPersister(), id, batchSizes[0] ); final int numberOfIds = ArrayHelper.countNonNull( batch ); if ( numberOfIds <= 1 ) { loaders[batchSizes.length-1].loadCollection( session, id, collectionPersister().getKeyType() ); return; } // Uses the first batch-size bigger than the number of actual ids in the batch int indexToUse = batchSizes.length-1; for ( int i = 0; i < batchSizes.length-1; i++ ) { if ( batchSizes[i] >= numberOfIds ) { indexToUse = i; } else { break; } } final Serializable[] idsToLoad = new Serializable[ batchSizes[indexToUse] ]; System.arraycopy( batch, 0, idsToLoad, 0, numberOfIds ); for ( int i = numberOfIds; i < batchSizes[indexToUse]; i++ ) { idsToLoad[i] = id; } loaders[indexToUse].loadCollectionBatch( session, idsToLoad, collectionPersister().getKeyType() ); } } }