/*
* JBoss, the OpenSource J2EE webOS
*
* Distributable under LGPL license.
* See terms of license at gnu.org.
*/
package org.jboss.cache.lock;
import EDU.oswego.cs.dl.util.concurrent.FIFOSemaphore;
import EDU.oswego.cs.dl.util.concurrent.Sync;
//import org.jboss.logging.Logger;
/**
* Lock strategy of Serializable that prevents dirty read, non-repeatable read, and
* phantom read.
* <p> Dirty read allows (t1) write and then (t2) read within two separate threads, all without
* transaction commit. </p>
* <p> Non-repeatable read allows (t1) read, (t2) write, and then (t1) read, all without
* transaction commit. </p>
* <p> Phantom read allows (t1) read n rows, (t2) insert k rows, and (t1) read n+k rows.</p>
*
* @author <a href="mailto:bwang00@sourceforge.net">Ben Wang</a> July 15, 2003
* @version $Revision: 13 $
*/
public class LockStrategySerializable implements LockStrategy
{
// Log log=LogFactory.getLog(getClass());
private int permits_;
private FIFOSemaphore sem_;
public LockStrategySerializable()
{
permits_ = 1;
sem_ = new FIFOSemaphore(permits_);
}
/**
* @see org.jboss.cache.lock.LockStrategy#readLock()
*/
public Sync readLock()
{
return sem_;
}
/**
* @see org.jboss.cache.lock.LockStrategy#upgradeLockAttempt(long)
*/
public Sync upgradeLockAttempt(long msecs) throws UpgradeException
{
// If we come to this far, that means the thread owns a rl already
// so we just return the same lock
return sem_;
}
/**
* @see org.jboss.cache.lock.LockStrategy#writeLock()
*/
public Sync writeLock()
{
return sem_;
}
}