namedqueryloader.java

介绍了hibernate的入门有一些基本常用的事例

//$Id: NamedQueryLoader.java,v 1.2 2005/02/16 12:50:17 oneovthafew Exp $
package org.hibernate.persister.entity;

import java.io.Serializable;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.AssertionFailure;
import org.hibernate.FlushMode;
import org.hibernate.HibernateException;
import org.hibernate.Query;
import org.hibernate.engine.EntityKey;
import org.hibernate.engine.SessionImplementor;
import org.hibernate.loader.entity.UniqueEntityLoader;

/**
 * Not really a <tt>Loader</tt>, just a wrapper around a
 * named query.
 * @author Gavin King
 */
public final class NamedQueryLoader implements UniqueEntityLoader {
	private final String queryName;
	private final EntityPersister persister;
	
	private static final Log log = LogFactory.getLog(NamedQueryLoader.class);

	public NamedQueryLoader(String queryName, EntityPersister persister) {
		super();
		this.queryName = queryName;
		this.persister = persister;
	}

	public Object load(Serializable id, Object optionalObject, SessionImplementor session) 
	throws HibernateException {
		
		if (optionalObject!=null) {
			throw new AssertionFailure("cannot supply object to query loader");
		}
		
		if ( log.isDebugEnabled() ) {
			log.debug("loading entity: " + persister.getEntityName() + " using named query: " + queryName );
		}
		
		Query query = session.getNamedQuery(queryName);
		if ( query.getNamedParameters().length>0 ) {
			query.setParameter( 
					query.getNamedParameters()[0], 
					id, 
					persister.getIdentifierType() 
			);
		}
		else {
			query.setParameter( 0, id, persister.getIdentifierType() );
		}
		query.setFlushMode(FlushMode.NEVER).list();
		
		// now look up the object we are really interested in!
		// (this lets us correctly handle proxies and multi-row
		// or multi-column queries)
		return session.getPersistenceContext().getEntity( new EntityKey( id, persister, session.getEntityMode() ) );

	}
}