//$Id: SequenceHiLoGenerator.java 9720 2006-03-31 00:11:54Z epbernard $
package org.hibernate.id;
import java.io.Serializable;
import java.util.Properties;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.HibernateException;
import org.hibernate.MappingException;
import org.hibernate.dialect.Dialect;
import org.hibernate.engine.SessionImplementor;
import org.hibernate.type.Type;
import org.hibernate.util.PropertiesHelper;
/**
* <b>seqhilo</b><br>
* <br>
* An <tt>IdentifierGenerator</tt> that combines a hi/lo algorithm with an underlying
* oracle-style sequence that generates hi values. The user may specify a
* maximum lo value to determine how often new hi values are fetched.<br>
* <br>
* If sequences are not available, <tt>TableHiLoGenerator</tt> might be an
* alternative.<br>
* <br>
* Mapping parameters supported: sequence, max_lo, parameters.
*
* @see TableHiLoGenerator
* @author Gavin King
*/
public class SequenceHiLoGenerator extends SequenceGenerator {
public static final String MAX_LO = "max_lo";
private static final Log log = LogFactory.getLog(SequenceHiLoGenerator.class);
private int maxLo;
private int lo;
private long hi;
private Class returnClass;
public void configure(Type type, Properties params, Dialect d) throws MappingException {
super.configure(type, params, d);
maxLo = PropertiesHelper.getInt(MAX_LO, params, 9);
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 );
if ( log.isDebugEnabled() )
log.debug("new hi value: " + hival);
}
return IdentifierGeneratorFactory.createNumber( hi + lo++, returnClass );
}
}
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