/**
* Redistribution and use of this software and associated documentation
* ("Software"), with or without modification, are permitted provided
* that the following conditions are met:
*
* 1. Redistributions of source code must retain copyright
* statements and notices. Redistributions must also contain a
* copy of this document.
*
* 2. Redistributions in binary form must reproduce the
* above copyright notice, this list of conditions and the
* following disclaimer in the documentation and/or other
* materials provided with the distribution.
*
* 3. The name "Exolab" must not be used to endorse or promote
* products derived from this Software without prior written
* permission of Intalio, Inc. For written permission,
* please contact info@exolab.org.
*
* 4. Products derived from this Software may not be called "Exolab"
* nor may "Exolab" appear in their names without prior written
* permission of Intalio, Inc. Exolab is a registered
* trademark of Intalio, Inc.
*
* 5. Due credit should be given to the Exolab Project
* (http://www.exolab.org/).
*
* THIS SOFTWARE IS PROVIDED BY INTALIO, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
* NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
* INTALIO, INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Copyright 1999 (C) Intalio, Inc. All Rights Reserved.
*
* $Id: QueryResults.java 7951 2008-10-09 20:52:17Z wguttmn $
*/
package org.exolab.castor.persist;
import javax.transaction.Status;
import org.castor.core.util.Messages;
import org.castor.persist.ProposedEntity;
import org.castor.persist.TransactionContext;
import org.exolab.castor.jdo.Database;
import org.exolab.castor.jdo.PersistenceException;
import org.exolab.castor.jdo.TransactionNotInProgressException;
import org.exolab.castor.mapping.AccessMode;
import org.exolab.castor.persist.spi.Identity;
import org.exolab.castor.persist.spi.PersistenceQuery;
/**
* The result of a query in the context of a transaction. A query is
* executed against the cache engine in the context of a transaction.
* The result of a query is this object that can be used to obtain
* the next object in the query.
*
* @author <a href="arkin@intalio.com">Assaf Arkin</a>
* @version $Revision: 7951 $ $Date: 2006-04-22 11:05:30 -0600 (Sat, 22 Apr 2006) $
*/
public final class QueryResults {
/**
* The transaction context in which this query was executed.
*/
private final TransactionContext _tx;
/**
* The persistence engine against which this query was executed.
*/
private final LockEngine _engine;
/**
* The executed query.
*/
private final PersistenceQuery _query;
/**
* The mode in which this query is running.
*/
private final AccessMode _accessMode;
/**
* The last identity retrieved with a call to {@link #nextIdentity}.
*/
private Identity _lastIdentity;
public QueryResults(final TransactionContext tx,
final LockEngine engine,
final PersistenceQuery query,
final AccessMode accessMode,
final Database db) {
_tx = tx;
_engine = engine;
_query = query;
_accessMode = engine.getClassMolder(_query.getResultType()).getAccessMode(accessMode);
}
/**
* Returns the transaction context in which this query was opened.
* The transaction may be closed.
*
* @return The query's transaction context
*/
public TransactionContext getTransaction() {
return _tx;
}
/**
* Returns the associated query.
*
* @return The query
*/
public PersistenceQuery getQuery() {
return _query;
}
/**
* Returns the type of object returned by this query.
*
* @return The type of object returned by this query
*/
public Class getResultType() {
return _query.getResultType();
}
/**
* Returns the identity of the next object to be returned.
* Calling this method multiple time will skip objects.
* When the result set has been exhuasted, this method will
* return null.
*
* @return The identity of the next object
* @throws PersistenceException An error reported by the
* persistence engine
* @throws TransactionNotInProgressException The transaction
* has been closed
*/
public Object nextIdentity() throws PersistenceException {
// Make sure transaction is still open.
if (_tx.getStatus() != Status.STATUS_ACTIVE) {
throw new TransactionNotInProgressException(
Messages.message("persist.noTransaction"));
}
try {
_lastIdentity = _query.nextIdentity(_lastIdentity);
} catch (PersistenceException except) {
_lastIdentity = null;
throw except;
}
return _lastIdentity;
}
/**
* Loads the specified object with the identity. The identity must
* have been retrieved with a call to {@link #nextIdentity}.
* <p>
* If the object is locked by another transaction this method will
* block until the lock is released, or a timeout occured. If a
* timeout occurs or the object has been deleted by the other
* transaction, this method will report an. The query may proceed to the next
* identity.
* <p>
* If the object has been deleted in this transaction, this method
* will report an. However, the caller may iterate to and obtain the next object.
* <p>
* This method is equivalent to {@link TransactionContext#fetch}
* with a know cache engine, identity and lock and acts on the query
* results rather than issuing a new query to load the object.
*
* @return The loaded object
* @throws PersistenceException An error reported by the persistence engine. The object was
* not found in persistent storage. The transaction has been closed. Could not
* acquire a lock on the object.
*/
public Object fetch() throws PersistenceException {
ClassMolder handler;
Object object;
// Make sure transaction is still open.
if (_tx.getStatus() != Status.STATUS_ACTIVE) {
throw new TransactionNotInProgressException(Messages
.message("persist.noTransaction"));
}
if (_lastIdentity == null) {
throw new IllegalStateException(Messages.message("jdo.fetchNoNextIdentity"));
}
handler = _engine.getClassMolder(_query.getResultType());
// load the object thur the transaction of the query
ProposedEntity proposedValue = new ProposedEntity(handler);
proposedValue.setProposedEntityClass(_query.getResultType());
object = _tx.load(_lastIdentity, proposedValue, _accessMode, this);
if (proposedValue.isExpanded()) { object = proposedValue.getEntity(); }
return object;
}
/**
* Close the query and release all resources held by the query.
*/
public void close() {
_query.close();
}
public boolean absolute(final int row) throws PersistenceException {
return _query.absolute(row);
}
public int size() throws PersistenceException {
return _query.size();
}
}