/*
* JBoss, Home of Professional Open Source.
* Copyright 2008, Red Hat Middleware LLC, and individual contributors
* as indicated by the @author tags. See the copyright.txt file in the
* distribution for a full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software 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 software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.jboss.aspects.versioned;
import java.util.concurrent.Semaphore;
import org.jboss.aop.Advised;
import org.jboss.aop.util.MarshalledValue;
import org.jboss.tm.TransactionLocal;
import javax.transaction.Status;
import javax.transaction.Synchronization;
import javax.transaction.Transaction;
/**
* Manages transactional versions of an object
* versioned object must be Serializable or Cloneable
*
* @author <a href="mailto:bill@jboss.org">Bill Burke</a>
* @version $Revision: 89144 $
*/
public class VersionedObject
{
Semaphore lock = new Semaphore(1, true);
TransactionLocal txLocal = new TransactionLocal();
long currentId = 0;
Object currentObject;
long versionIdGenerator = 0;
public VersionedObject(Object obj)
{
currentObject = obj;
}
public Object getVersion(Transaction tx)
{
if (tx == null) return currentObject;
return txLocal.get(tx);
}
public Object createVersion(Transaction tx) throws Exception
{
final Object version;
final long versionId;
lock.acquire();
try
{
version = new MarshalledValue(currentObject).get();
if (version instanceof Advised)
{
// REVISIT: Currently share the InstanceAdvisor between versions
Advised versionAdvised = (Advised)version;
Advised currentAdvised = (Advised)currentObject;
versionAdvised._setInstanceAdvisor(currentAdvised._getInstanceAdvisor());
}
versionId = ++versionIdGenerator;
}
finally
{
lock.release();
}
tx.registerSynchronization(new VersionSynchronization(tx, versionId, version));
txLocal.set(tx, version);
return version;
}
private final class VersionSynchronization implements Synchronization
{
long versionId;
Object version;
Transaction tx;
public VersionSynchronization(Transaction tx, long versionId, Object version)
{
this.tx = tx;
this.versionId = versionId;
this.version = version;
}
public void beforeCompletion()
{
try
{
lock.acquire();
}
catch (InterruptedException ignored)
{
throw new RuntimeException(ignored);
}
if (currentId >= versionId)
{
lock.release();
throw new OptimisticLockFailure();
}
}
public void afterCompletion(int status)
{
//possible status is committed and rolledback
if (status != Status.STATUS_ROLLEDBACK)
{
currentId = versionId;
currentObject = version;
lock.release();
}
}
}
}