tablehilogenerator.java

来自「hibernate-distribution-3.3.1.GA-dist.zip」· Java 代码 · 共 95 行

/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2008, Red Hat Middleware LLC 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 Middleware LLC.
 *
 * 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.id;

import java.io.Serializable;
import java.util.Properties;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.hibernate.HibernateException;
import org.hibernate.dialect.Dialect;
import org.hibernate.engine.SessionImplementor;
import org.hibernate.type.Type;
import org.hibernate.util.PropertiesHelper;

/**
 * <b>hilo</b><br>
 * <br>
 * An <tt>IdentifierGenerator</tt> that returns a <tt>Long</tt>, constructed using
 * a hi/lo algorithm. The hi value MUST be fetched in a seperate transaction
 * to the <tt>Session</tt> transaction so the generator must be able to obtain
 * a new connection and commit it. Hence this implementation may not
 * be used  when the user is supplying connections. In this
 * case a <tt>SequenceHiLoGenerator</tt> would be a better choice (where
 * supported).<br>
 * <br>
 * Mapping parameters supported: table, column, max_lo
 *
 * @see SequenceHiLoGenerator
 * @author Gavin King
 */
public class TableHiLoGenerator extends TableGenerator {

	/**
	 * The max_lo parameter
	 */
	public static final String MAX_LO = "max_lo";

	private long hi;
	private int lo;
	private int maxLo;
	private Class returnClass;

	private static final Logger log = LoggerFactory.getLogger(TableHiLoGenerator.class);

	public void configure(Type type, Properties params, Dialect d) {
		super.configure(type, params, d);
		maxLo = PropertiesHelper.getInt(MAX_LO, params, Short.MAX_VALUE);
		lo = maxLo + 1; // so we "clock over" on the first invocation
		returnClass = type.getReturnedClass();
	}

	public synchronized Serializable generate(SessionImplementor session, Object obj) 
	throws HibernateException {
        if (maxLo < 1) {
			//keep the behavior consistent even for boundary usages
			long val = ( (Number) super.generate(session, obj) ).longValue();
			if (val == 0) val = ( (Number) super.generate(session, obj) ).longValue();
			return IdentifierGeneratorFactory.createNumber( val, returnClass );
		}
		if (lo>maxLo) {
			long hival = ( (Number) super.generate(session, obj) ).longValue();
			lo = (hival == 0) ? 1 : 0;
			hi = hival * (maxLo+1);
			log.debug("new hi value: " + hival);
		}

		return IdentifierGeneratorFactory.createNumber( hi + lo++, returnClass );

	}

}