/src/com/google/appengine/datanucleus/DatastoreXAResource.java

/**********************************************************************

Copyright (c) 2009 Google Inc.



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.

**********************************************************************/

package com.google.appengine.datanucleus;



import com.google.appengine.api.datastore.DatastoreService;

import com.google.appengine.api.datastore.Transaction;

import com.google.appengine.api.datastore.TransactionOptions;



import org.datanucleus.util.NucleusLogger;



import javax.transaction.xa.XAException;

import javax.transaction.xa.Xid;



/**

 * Extension to {@link EmulatedXAResource} that manages a transaction against the datastore.

 * Currently only supports a single, non-distributed transaction.  Instances of this class are

 * instantiated and used when the datasource has been configured as "autoCreateTransaction" or the user is

 * explicitly doing transaction management.

 *

 * @author Erick Armbrust <earmbrust@google.com>

 * @author Max Ross <maxr@google.com>

 */

class DatastoreXAResource extends EmulatedXAResource {



  /** The current datastore transaction. */

  private DatastoreTransaction currentTxn;

  private final TransactionOptions txnOpts;



  public DatastoreXAResource(DatastoreService datastoreService, TransactionOptions txnOpts) {

    super(datastoreService);

    this.txnOpts = txnOpts;

  }



  @Override

  DatastoreTransaction getCurrentTransaction() {

    return currentTxn;

  }



  @Override

  public void start(Xid xid, int flags) throws XAException {

    super.start(xid, flags);

    if (currentTxn == null) {

      // No currentTxn, and DatastoreService will have been created by DatastoreConnectionFactoryImpl, so call beginTxn

      Transaction datastoreTxn = datastoreService.beginTransaction(txnOpts);

      currentTxn = new DatastoreTransaction(datastoreTxn);

      if (NucleusLogger.TRANSACTION.isDebugEnabled()) {

        NucleusLogger.TRANSACTION.debug(

            LOCALISER.msg("AppEngine.Transaction.Started", currentTxn.getInnerTxn().getId()));

      }

    } else {

      throw new XAException(LOCALISER.msg("AppEngine.Transaction.AlreadyStarted"));

    }

  }



  @Override

  public void commit(Xid xid, boolean onePhase) throws XAException {

    super.commit(xid, onePhase);

    if (currentTxn != null) {

      currentTxn.commit();

      if (NucleusLogger.TRANSACTION.isDebugEnabled()) {

        NucleusLogger.TRANSACTION.debug(

            LOCALISER.msg("AppEngine.Transaction.Committed", currentTxn.getInnerTxn().getId()));

      }

      currentTxn = null;

    } else {

      throw new XAException(LOCALISER.msg("AppEngine.Transaction.CommitInvalid"));

    }

  }



  @Override

  public void rollback(Xid xid) throws XAException {

    super.rollback(xid);

    if (currentTxn != null) {

      currentTxn.rollback();

      if (NucleusLogger.TRANSACTION.isDebugEnabled()) {

        NucleusLogger.TRANSACTION.debug(

            LOCALISER.msg("AppEngine.Transaction.RolledBack", currentTxn.getInnerTxn().getId()));

      }

      currentTxn = null;

    } else {

      throw new XAException(LOCALISER.msg("AppEngine.Transaction.RollbackInvalid"));

    }

  }

}