I'm using JBossCache 1.01 with Hibernate. The IsolationLevel I'm using is NONE. I got this NPE:

2004-06-12 15:41:19,348 ERROR [UpHandler (GMS)] org.jboss.cache.TreeCache - getState(): failed lock
ing
tree
java.lang.NullPointerException
at org.jboss.cache.lock.IdentityLock.acquireReadLock(IdentityLock.java:175)
at org.jboss.cache.Node.acquireReadLock(Node.java:346)
at org.jboss.cache.Node.acquire(Node.java:331)
at org.jboss.cache.Node.acquireAll(Node.java:370)
at org.jboss.cache.TreeCache$MessageListenerAdaptor.getState(TreeCache.java:2438)
at org.jgroups.blocks.MessageDispatcher$ProtocolAdapter.passUp(MessageDispatcher.java:576)
at org.jgroups.blocks.RequestCorrelator.receive(RequestCorrelator.java:322)
at org.jgroups.blocks.MessageDispatcher$ProtocolAdapter.up(MessageDispatcher.java:638)
at org.jgroups.JChannel.up(JChannel.java:874)
at org.jgroups.stack.ProtocolStack.up(ProtocolStack.java:323)
at org.jgroups.stack.ProtocolStack.receiveUpEvent(ProtocolStack.java:339)
at org.jgroups.stack.Protocol.passUp(Protocol.java:489)
at org.jgroups.protocols.pbcast.STATE_TRANSFER.up(STATE_TRANSFER.java:102)
at org.jgroups.stack.Protocol.receiveUpEvent(Protocol.java:437)
at org.jgroups.stack.Protocol.passUp(Protocol.java:489)
at org.jgroups.protocols.pbcast.GMS.up(GMS.java:582)
at org.jgroups.stack.UpHandler.run(Protocol.java:60)

I had to add a class called LockStrategyNone. I guess this has been on the todo list since there was a comment "FIXME Ben" in the source code of LockStrategyFactory:

if (lockingLevel_ == null || lockingLevel_ == IsolationLevel.NONE)
 return null; // FIXME Ben !

if (lockingLevel_ == null || lockingLevel_ == IsolationLevel.NONE)
 return new LockStrategyNone();

/*
 * JBoss, the OpenSource J2EE webOS
 *
 * Distributable under LGPL license.
 * See terms of license at gnu.org.
 */
package org.jboss.cache.lock;

import EDU.oswego.cs.dl.util.concurrent.NullSync;
import EDU.oswego.cs.dl.util.concurrent.Sync;

/**
 * Transaction isolation level of None.
 *
 * @author Lari Hotari
 * @version $Revision$
 */
public class LockStrategyNone implements LockStrategy
{
 private NullSync nullLock_;

 public LockStrategyNone()
 {
 nullLock_ = new NullSync();
 }

 /**
 * @see org.jboss.cache.LockStrategy#readLock()
 */
 public Sync readLock()
 {
 return nullLock_;
 }

 /**
 * @see org.jboss.cache.LockStrategy#upgradeLockAttempt(long)
 */
 public Sync upgradeLockAttempt(long msecs)
 {
 return nullLock_;
 }

 /**
 * @see org.jboss.cache.LockStrategy#writeLock()
 */
 public Sync writeLock()
 {
 return nullLock_;
 }
}

/*
 * JBoss, the OpenSource J2EE webOS
 *
 * Distributable under LGPL license.
 * See terms of license at gnu.org.
 */
package org.jboss.cache.lock;

/**
 * Factory to create LockStragtegy instance.
 *
 * @author Ben Wang
 */
public class LockStrategyFactory
{
 private static LockStrategyFactory s_me = null;


 /**
 * Transaction locking isolation level. Default.
 */
 private static IsolationLevel lockingLevel_ = IsolationLevel.REPEATABLE_READ;

 /**
 *
 */
 protected LockStrategyFactory()
 {
 }

 public static LockStrategyFactory getInstance()
 {
 if (s_me == null)
 s_me = new LockStrategyFactory();

 return s_me;
 }

 public LockStrategy getLockStrategy()
 {
 if (lockingLevel_ == null || lockingLevel_ == IsolationLevel.NONE)
 return new LockStrategyNone();
 if (lockingLevel_ == IsolationLevel.REPEATABLE_READ)
 return new LockStrategyRepeatableRead();
 if (lockingLevel_ == IsolationLevel.SERIALIZABLE)
 return new LockStrategySerializable();
 if (lockingLevel_ == IsolationLevel.READ_COMMITTED)
 return new LockStrategyReadCommitted();
 if (lockingLevel_ == IsolationLevel.READ_UNCOMMITTED)
 return new LockStrategyReadUncommitted();
 throw new RuntimeException("getLockStrategy: LockStrategy selection not recognized." +
 " selection: " + lockingLevel_);
 }

 public static void setIsolationLevel(IsolationLevel level)
 {
 lockingLevel_ = level;
 }

}