package org.apache.ojb.otm.lock;

 /* 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.broker.Identity;

 import org.apache.ojb.broker.PersistenceBroker;

 import org.apache.ojb.otm.core.Transaction;

 import org.apache.ojb.otm.lock.isolation.TransactionIsolation;

 import org.apache.ojb.otm.lock.map.LockMap;

 /**

  *

  * Manages locks on objects across transactions.

  *

  * @author <a href="mailto:rraghuram@hotmail.com">Raghu Rajah</a>

  *

  */

 public class LockManager

 {

     private static LockManager _Instance = new LockManager();

     public static LockManager getInstance ()

     {

         return _Instance;

     }

     private LockManager()

     {

     }

     public void ensureLock(Identity oid, Transaction tx, int lock,

                            PersistenceBroker pb)

         throws LockingException

     {

         LockMap lockMap = tx.getKit().getLockMap();

         ObjectLock objectLock = lockMap.getLock(oid);

         TransactionIsolation isolation;

         isolation = IsolationFactory.getIsolationLevel(pb, objectLock);

         if (lock == LockType.READ_LOCK)

         {

             isolation.readLock(tx, objectLock);

         }

         else if (lock == LockType.WRITE_LOCK)

         {

             isolation.writeLock(tx, objectLock);

         }

     }

     public int getLockHeld(Identity oid, Transaction tx)

     {

         LockMap lockMap = tx.getKit().getLockMap();

         ObjectLock lock = lockMap.getLock(oid);

         int lockHeld = LockType.NO_LOCK;

         if (tx.equals(lock.getWriter()))

         {

             lockHeld = LockType.WRITE_LOCK;

         }

         else if (lock.isReader(tx))

         {

             lockHeld = LockType.READ_LOCK;

         }

         return lockHeld;

     }

     public void releaseLock(Identity oid, Transaction tx)

     {

         LockMap lockMap = tx.getKit().getLockMap();

         ObjectLock objectLock = lockMap.getLock(oid);

         objectLock.releaseLock(tx);

     }

 }