org.hibernate.id.AbstractUUIDGenerator Maven / Gradle / Ivy
/*
* 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.net.InetAddress;
import org.hibernate.internal.util.BytesHelper;
/**
* The base class for identifier generators that use a UUID algorithm. This
* class implements the algorithm, subclasses define the identifier
* format.
*
* @see UUIDHexGenerator
* @author Gavin King
*/
public abstract class AbstractUUIDGenerator implements IdentifierGenerator {
private static final int IP;
static {
int ipadd;
try {
ipadd = BytesHelper.toInt( InetAddress.getLocalHost().getAddress() );
}
catch (Exception e) {
ipadd = 0;
}
IP = ipadd;
}
private static short counter = (short) 0;
private static final int JVM = (int) ( System.currentTimeMillis() >>> 8 );
public AbstractUUIDGenerator() {
}
/**
* Unique across JVMs on this machine (unless they load this class
* in the same quater second - very unlikely)
*/
protected int getJVM() {
return JVM;
}
/**
* Unique in a millisecond for this JVM instance (unless there
* are > Short.MAX_VALUE instances created in a millisecond)
*/
protected short getCount() {
synchronized(AbstractUUIDGenerator.class) {
if (counter<0) counter=0;
return counter++;
}
}
/**
* Unique in a local network
*/
protected int getIP() {
return IP;
}
/**
* Unique down to millisecond
*/
protected short getHiTime() {
return (short) ( System.currentTimeMillis() >>> 32 );
}
protected int getLoTime() {
return (int) System.currentTimeMillis();
}
}