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* JBoss, Home of Professional Open Source
* Copyright 2009 Red Hat Inc. and/or its affiliates and other
* contributors as indicated by the @author tags. All rights reserved.
* See the copyright.txt in the distribution for a full listing of
* individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.infinispan.container.entries;
import org.infinispan.container.DataContainer;
import org.infinispan.transaction.WriteSkewException;
import org.infinispan.util.logging.Log;
import org.infinispan.util.logging.LogFactory;
import org.infinispan.container.versioning.EntryVersion;
/**
* An extension of {@link ReadCommittedEntry} that provides Repeatable Read semantics
*
* @author Manik Surtani (<a href="mailto:manik@jboss.org">manik@jboss.org</a>)
* @since 4.0
*/
public class RepeatableReadEntry extends ReadCommittedEntry {
private static final Log log = LogFactory.getLog(RepeatableReadEntry.class);
public RepeatableReadEntry(Object key, Object value, EntryVersion version, long lifespan) {
super(key, value, version, lifespan);
}
@Override
public void copyForUpdate(DataContainer container, boolean localModeWriteSkewCheck) {
if (isChanged()) return; // already copied
// mark entry as changed.
setChanged();
if (localModeWriteSkewCheck) {
performLocalWriteSkewCheck(container, false);
}
// make a backup copy
oldValue = value;
}
public void performLocalWriteSkewCheck(DataContainer container, boolean alreadyCopied) {
// check for write skew.
InternalCacheEntry ice = container.get(key);
Object actualValue = ice == null ? null : ice.getValue();
Object valueToCompare = alreadyCopied ? oldValue : value;
// Note that this identity-check is intentional. We don't *want* to call actualValue.equals() since that defeats the purpose.
// the implicit "versioning" we have in R_R creates a new wrapper "value" instance for every update.
if (actualValue != null && actualValue != valueToCompare) {
log.unableToCopyEntryForUpdate(getKey());
throw new WriteSkewException("Detected write skew.");
}
if (ice == null && !isCreated()) {
// We still have a write-skew here. When this wrapper was created there was an entry in the data container
// (hence isCreated() == false) but 'ice' is now null.
log.unableToCopyEntryForUpdate(getKey());
throw new WriteSkewException("Detected write skew - concurrent removal of entry!");
}
}
}