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 java.util.Collection;
import org.apache.ojb.otm.core.Transaction;
import org.apache.ojb.otm.lock.LockingException;
import org.apache.ojb.otm.lock.ObjectLock;
public class SerializableIsolation extends AbstractIsolation
{
/**
* @see org.apache.ojb.otm.lock.isolation.TransactionIsolation#readLock(Transaction, ObjectLock)
*/
public void readLock (Transaction tx, ObjectLock lock)
throws LockingException
{
Collection readers = lock.getReaders();
if (readers.isEmpty())
{
lock.readLock(tx);
readers = lock.getReaders();
if (readers.size() > 1)
{
lock.releaseLock(tx);
readLock(tx, lock);
}
}
else
{
Transaction reader = (Transaction) readers.iterator().next();
if (reader != tx) {
lock.waitForTx(reader);
}
}
}
/**
* @see org.apache.ojb.otm.lock.isolation.TransactionIsolation#writeLock(Transaction, ObjectLock)
*/
public void writeLock (Transaction tx, ObjectLock lock)
throws LockingException
{
Collection readers = lock.getReaders();
if (readers.isEmpty())
{
readLock(tx, lock);
writeLock(tx, lock);
}
else
{
Transaction reader = (Transaction) readers.iterator().next();
if (reader == tx)
{
lock.writeLock(tx);
}
else
{
lock.waitForTx(reader);
writeLock(tx, lock);
}
}
}
}