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* as indicated by the @author tags. See the copyright.txt file in the
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*
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* under the terms of the GNU Lesser General Public License as
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*
* This software is distributed in the hope that it will be useful,
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
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package org.jboss.cache.mvcc;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.jboss.cache.DataContainer;
import org.jboss.cache.Fqn;
import org.jboss.cache.InternalNode;
import org.jboss.cache.InvocationContext;
import static org.jboss.cache.mvcc.ReadCommittedNode.Flags.CHANGED;
import static org.jboss.cache.mvcc.ReadCommittedNode.Flags.DELETED;
import org.jboss.cache.optimistic.DataVersioningException;
/**
* A node delegate that encapsulates repeatable read semantics when writes are initiated, committed or rolled back.
*
* @author Manik Surtani (<a href="mailto:manik AT jboss DOT org">manik AT jboss DOT org</a>)
* @since 3.0
*/
public class RepeatableReadNode extends ReadCommittedNode
{
private static final Log log = LogFactory.getLog(RepeatableReadNode.class);
public RepeatableReadNode(InternalNode node, InternalNode parent)
{
super(node, parent);
}
@Override
public void markForUpdate(DataContainer container, boolean writeSkewCheck)
{
if (isFlagSet(CHANGED)) return; // already copied
Fqn fqn = getFqn();
// mark node as changed.
setFlag(CHANGED);
if (writeSkewCheck)
{
// check for write skew.
InternalNode underlyingNode = container.peekInternalNode(fqn, true);
if (underlyingNode != null && underlyingNode != node)
{
String errormsg = new StringBuilder().append("Detected write skew on Fqn [").append(fqn).append("]. Another process has changed the node since we last read it!").toString();
if (log.isWarnEnabled()) log.warn(errormsg + ". Unable to copy node for update.");
throw new DataVersioningException(errormsg);
}
}
// make a backup copy
backup = node;
node = backup.copy();
}
@Override
@SuppressWarnings("unchecked")
protected void updateNode(Fqn fqn, InvocationContext ctx, DataContainer dataContainer)
{
if (fqn.isRoot())
{
dataContainer.setRoot(node);
}
else if (!isFlagSet(DELETED))
{
InternalNode parent = lookupParent(fqn, ctx, dataContainer);
parent.addChild(node, true); // we know this is safe since we calculated the parent from the child. No need to have the parent re-do checks when adding the child again.
}
}
}