//$Id: TableHiLoGenerator.java 11124 2007-01-31 23:46:25Z [email protected] $
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.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 Log log = LogFactory.getLog(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 );
}
}
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