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A module of the Hibernate Core project
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/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2008, 2012, Red Hat Inc. or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Inc.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */
package org.hibernate.loader.entity;

import java.io.Serializable;
import java.sql.SQLException;
import java.util.Arrays;
import java.util.List;

import org.jboss.logging.Logger;

import org.hibernate.LockOptions;
import org.hibernate.engine.spi.QueryParameters;
import org.hibernate.engine.spi.SessionImplementor;
import org.hibernate.loader.Loader;
import org.hibernate.persister.entity.EntityPersister;
import org.hibernate.pretty.MessageHelper;
import org.hibernate.type.Type;

/**
 * The base contract for loaders capable of performing batch-fetch loading of entities using multiple primary key
 * values in the SQL WHERE clause.
 *
 * @author Gavin King
 * @author Steve Ebersole
 *
 * @see BatchingEntityLoaderBuilder
 * @see UniqueEntityLoader
 */
public abstract class BatchingEntityLoader implements UniqueEntityLoader {
	private static final Logger log = Logger.getLogger( BatchingEntityLoader.class );

	private final EntityPersister persister;

	public BatchingEntityLoader(EntityPersister persister) {
		this.persister = persister;
	}

	public EntityPersister persister() {
		return persister;
	}

	@Override
	@Deprecated
	public Object load(Serializable id, Object optionalObject, SessionImplementor session) {
		return load( id, optionalObject, session, LockOptions.NONE );
	}

	protected QueryParameters buildQueryParameters(
			Serializable id,
			Serializable[] ids,
			Object optionalObject,
			LockOptions lockOptions) {
		Type[] types = new Type[ids.length];
		Arrays.fill( types, persister().getIdentifierType() );

		QueryParameters qp = new QueryParameters();
		qp.setPositionalParameterTypes( types );
		qp.setPositionalParameterValues( ids );
		qp.setOptionalObject( optionalObject );
		qp.setOptionalEntityName( persister().getEntityName() );
		qp.setOptionalId( id );
		qp.setLockOptions( lockOptions );
		return qp;
	}

	protected Object getObjectFromList(List results, Serializable id, SessionImplementor session) {
		for ( Object obj : results ) {
			final boolean equal = persister.getIdentifierType().isEqual(
					id,
					session.getContextEntityIdentifier( obj ),
					session.getFactory()
			);
			if ( equal ) {
				return obj;
			}
		}
		return null;
	}

	protected Object doBatchLoad(
			Serializable id,
			Loader loaderToUse,
			SessionImplementor session,
			Serializable[] ids,
			Object optionalObject,
			LockOptions lockOptions) {
		if ( log.isDebugEnabled() ) {
			log.debugf( "Batch loading entity: %s", MessageHelper.infoString( persister, ids, session.getFactory() ) );
		}

		QueryParameters qp = buildQueryParameters( id, ids, optionalObject, lockOptions );

		try {
			final List results = loaderToUse.doQueryAndInitializeNonLazyCollections( session, qp, false );
			log.debug( "Done entity batch load" );
			return getObjectFromList(results, id, session);
		}
		catch ( SQLException sqle ) {
			throw session.getFactory().getSQLExceptionHelper().convert(
					sqle,
					"could not load an entity batch: " + MessageHelper.infoString( persister(), ids, session.getFactory() ),
					loaderToUse.getSQLString()
			);
		}
	}

}