package org.apache.ojb.otm.lock.isolation;
/* Copyright 2003-2005 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import org.apache.ojb.otm.core.Transaction;
import org.apache.ojb.otm.lock.LockingException;
import org.apache.ojb.otm.lock.ObjectLock;
/**
*
* READ_COMMITTED IsolationStrategy.
*
* @author <a href="mailto:rraghuram@hotmail.com">Raghu Rajah</a>
* @author Thomas Mahler & David Dixon-Peugh
*
*/
public class ReadCommittedIsolation extends AbstractIsolation
{
/**
* @see org.apache.ojb.otm.lock.TransactionIsolation#readLock(Transaction, ObjectLocks)
*/
public void readLock(Transaction tx, ObjectLock lock)
throws LockingException
{
Transaction writer = lock.getWriter();
if (writer == null)
{
lock.readLock(tx);
if (lock.getWriter() != null)
{
lock.releaseLock(tx);
readLock(tx, lock);
}
}
else if (tx != writer)
{
lock.waitForTx(writer);
readLock(tx, lock);
}
// else if tx is the writer, it can also read.
}
/**
* @see org.apache.ojb.otm.lock.TransactionIsolation#writeLock(Transaction, ObjectLocks)
*/
public void writeLock(Transaction tx, ObjectLock lock)
throws LockingException
{
lock.writeLock(tx);
}
}