ObjectManagerImpl.java :  » Database-Client » DataNucleus--2.1.0 » org » datanucleus » Java Open Source

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DataNucleus 2.1.0 » org » datanucleus » ObjectManagerImpl.java
/**********************************************************************
Copyright (c) 2006 Andy Jefferson and others. All rights reserved.
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.

Contributors:
2007 Xuan Baldauf - added the use of srm.findObject() to cater for different object lifecycle management policies (in RDBMS and DB4O databases)
2007 Xuan Baldauf - changes to allow the disabling of clearing of fields when transitioning from PERSISTENT_NEW to TRANSIENT.
2008 Marco Schulze - added reference counting functionality for get/acquireThreadContextInfo()
     ...
 **********************************************************************/
package org.datanucleus;

import java.lang.reflect.Constructor;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.datanucleus.api.ApiAdapter;
import org.datanucleus.cache.CachedPC;
import org.datanucleus.cache.Level1Cache;
import org.datanucleus.cache.Level2Cache;
import org.datanucleus.exceptions.ClassNotDetachableException;
import org.datanucleus.exceptions.ClassNotPersistableException;
import org.datanucleus.exceptions.ClassNotResolvedException;
import org.datanucleus.exceptions.CommitStateTransitionException;
import org.datanucleus.exceptions.NoPersistenceInformationException;
import org.datanucleus.exceptions.NucleusException;
import org.datanucleus.exceptions.NucleusObjectNotFoundException;
import org.datanucleus.exceptions.NucleusOptimisticException;
import org.datanucleus.exceptions.NucleusUserException;
import org.datanucleus.exceptions.ObjectDetachedException;
import org.datanucleus.exceptions.RollbackStateTransitionException;
import org.datanucleus.exceptions.TransactionActiveOnCloseException;
import org.datanucleus.exceptions.TransactionNotActiveException;
import org.datanucleus.identity.DatastoreUniqueOID;
import org.datanucleus.identity.IdentityTranslator;
import org.datanucleus.identity.OID;
import org.datanucleus.identity.OIDFactory;
import org.datanucleus.identity.SCOID;
import org.datanucleus.jdo.NucleusJDOHelper;
import org.datanucleus.metadata.AbstractClassMetaData;
import org.datanucleus.metadata.IdentityType;
import org.datanucleus.metadata.MetaDataManager;
import org.datanucleus.metadata.TransactionType;
import org.datanucleus.state.CallbackHandler;
import org.datanucleus.state.DetachState;
import org.datanucleus.state.FetchPlanState;
import org.datanucleus.state.StateManagerFactory;
import org.datanucleus.store.ExecutionContext;
import org.datanucleus.store.Extent;
import org.datanucleus.store.FieldValues;
import org.datanucleus.store.StoreManager;
import org.datanucleus.store.query.Query;
import org.datanucleus.util.Localiser;
import org.datanucleus.util.NucleusLogger;
import org.datanucleus.util.StringUtils;
import org.datanucleus.util.WeakValueMap;

/**
 * Representation of an ObjectManager.
 * An object manager provides management for the persistence of objects into a datastore
 * and the retrieval of these objects using various methods. 
 * <h3>Caching</h3>
 * <p>
 * An ObjectManager has its own Level 1 cache. This stores objects against their identity. The Level 1 cache
 * is typically a weak referenced map and so cached objects can be garbage collected. Objects are placed in the
 * Level 1 cache during the transaction. 
 * The ObjectManagerFactory also has a Level 2 cache. This is used to allow cross-communication between
 * ObjectManagers. Objects are placed in the Level 2 cache during commit() of a transaction. If an object is
 * deleted during a transaction then it will be removed from the Level 2 cache at commit(). If an object is
 * no longer enlisted in the transaction at commit then it will be removed from the Level 2 cache (so we
 * remove the chance of handing out old data).
 * </p>
 * <h3>Transactions</h3>
 * <p>
 * An ObjectManager has a single transaction (the "current" transaction). The transaction can be
 * "active" (if begin() has been called on it) or "inactive".
 * </p>
 * <h3>Persisted Objects</h3>
 * <p>
 * When an object involved in the current transaction it is <i>enlisted</i> (calling enlistInTransaction()).
 * Its' identity is saved (in "txEnlistedIds") for use later in any "persistenceByReachability" process run at commit.
 * Any object that is passed via makePersistent() will be stored (as an identity) in "txKnownPersistedIds" and objects 
 * persisted due to reachability from these objects will also have their identity stored (in "txFlushedNewIds").
 * All of this information is used in the "persistence-by-reachability-at-commit" process which detects if some objects
 * originally persisted are no longer reachable and hence should not be persistent after all.
 * </p>
 */
public class ObjectManagerImpl implements ObjectManager
{
    /** Localisation utility for output messages */
    protected static final Localiser LOCALISER = Localiser.getInstance("org.datanucleus.Localisation",
        ObjectManagerFactoryImpl.class.getClassLoader());

    /** Factory for this ObjectManager. */
    private final ObjectManagerFactoryImpl omf;

    /** The owning PersistenceManager/EntityManager object. */
    private Object owner;

    /** State variable for whether the ObjectManager is closed. */
    private boolean closed;

    /** Current FetchPlan for the ObjectManager. */
    private FetchPlan fetchPlan;

    /** The ClassLoader resolver to use for class loading issues. */
    private ClassLoaderResolver clr = null;

    /** Callback handler for this ObjectManager. */
    private CallbackHandler callbacks;

    //-- cache level 1 --//
    /** Level 1 Cache */
    private Level1Cache cache;

    /** Whether to ignore the cache */
    private boolean ignoreCache;

    //-- convenience operations --//
    /** State variable used when searching for the StateManager for an object, representing the object. */
    private Object objectLookingForStateManager = null;

    /** State variable used when searching for the StateManager for an object, representing the StateManager. */
    private StateManager foundStateManager = null;

    //-- transaction --//
    /** Current transaction */
    private Transaction tx;

    /** Cache of StateManagers enlisted in the current transaction, keyed by the object id. */
    private Map<Object, StateManager> enlistedSMCache = new WeakValueMap();

    /** Set of the object ids for all objects enlisted in this transaction. Used in reachability at commit to determine what to check. */
    private Set txEnlistedIds = new HashSet();

    /** List of StateManagers for all current dirty objects managed by this ObjectManager. */
    private List<StateManager> dirtySMs = new ArrayList(10);

    /** List of StateManagers for all current dirty objects made dirty by reachability. Only used by delete process currently. */
    private List<StateManager> indirectDirtySMs = new ArrayList();

    /** StateManagers of all objects that have had managed relationships changed in the last flush-cycle. */
    HashSet<StateManager> managedRelationDirtySMs = null;

    /** State indicator whether we are currently managing the relations. */
    private boolean managingRelations = false;

    /** Set of Object Ids of objects persisted using persistObject, or known as already persistent in the current transaction. */
    private Set txKnownPersistedIds = new HashSet();

    /** Set of Object Ids of objects deleted using deleteObject. */
    private Set txKnownDeletedIds = new HashSet();

    /** Set of Object Ids of objects newly persistent in the current transaction */
    private Set txFlushedNewIds = new HashSet();

    /** Set of ids to be Level2 cached at commit (if using L2 cache). */
    private Set txCachedIds = null;

    //-- configuration --//
    /** Whether to detach objects on close of the ObjectManager. */
    private boolean detachOnClose;

    /** Whether to detach all objects on commit of the transaction. */
    private boolean detachAllOnCommit;

    /** Whether to detach all objects on rollback of the transaction. */
    private boolean detachAllOnRollback;

    /** Policy on attaching. Whether to attach dirty fields only, or all fields. */
    private String attachPolicy;

    /** Whether to copy objects on attaching. */
    private boolean copyOnAttach;

    /** Whether to operate multithreaded */
    private boolean multithreaded;

    /** Datastore read timeout in milliseconds. */
    private Integer datastoreReadTimeoutMillis = null;

    /** Datastore write timeout in milliseconds. */
    private Integer datastoreWriteTimeoutMillis = null;

    /** State variable for whether the ObjectManager is currently flushing its operations. */
    private boolean flushing = false;

    /** State variable for whether we are currently running detachAllOnCommit/detachAllOnRollback. */
    private boolean runningDetachAllOnTxnEnd = false;

    /** Manager for dynamic fetch groups defined on the OMF. */
    private FetchGroupManager fetchGrpMgr;

    private ExecutionContext executionContext;
    
    /**
     * Thread-specific state information (instances of {@link ThreadContextInfo}) used where we don't want
     * to pass information down through a large number of method calls.
     */
    private ThreadLocal contextInfoThreadLocal = new ThreadLocal()
    {
        protected Object initialValue()
        {
            return new ThreadContextInfo();
        }
    };

    /**
     * Constructor.
     * @param omf Object Manager Factory
     * @param owner The owning PM/EM. This will be the PM until we split JPA from JDO
     * @param userName Username for the datastore
     * @param password Password for the datastore
     * @throws NucleusUserException if an error occurs allocating the necessary requested components
     */
    public ObjectManagerImpl(ObjectManagerFactoryImpl omf, Object owner, String userName, String password)
    {
        this.owner = owner;
        this.omf = omf;
        closed = false;
        this.executionContext = new ExecutionContextImpl(this);

        // Set up class loading
        ClassLoader contextLoader = Thread.currentThread().getContextClassLoader();
        clr = omf.getOMFContext().getClassLoaderResolver(contextLoader);
        try
        {
            ImplementationCreator ic = omf.getOMFContext().getImplementationCreator();
            if (ic != null)
            {
                clr.setRuntimeClassLoader(ic.getClassLoader());
            }
        }
        catch (Exception ex)
        {
            // do nothing
        }

        // Set up StoreManager, using that of the OMF
        if (NucleusLogger.PERSISTENCE.isDebugEnabled())
        {
            NucleusLogger.PERSISTENCE.debug(LOCALISER.msg("010000", this, omf.getOMFContext().getStoreManager()));
        }

        PersistenceConfiguration config = omf.getOMFContext().getPersistenceConfiguration();

        // Configuration from OMF
        setIgnoreCache(config.getBooleanProperty("datanucleus.IgnoreCache"));
        setDetachOnClose(config.getBooleanProperty("datanucleus.DetachOnClose"));
        setDetachAllOnCommit(config.getBooleanProperty("datanucleus.DetachAllOnCommit"));
        setDetachAllOnRollback(config.getBooleanProperty("datanucleus.DetachAllOnRollback"));
        setCopyOnAttach(config.getBooleanProperty("datanucleus.CopyOnAttach"));
        setAttachPolicy(config.getStringProperty("datanucleus.attachPolicy"));
        setMultithreaded(config.getBooleanProperty("datanucleus.Multithreaded"));
        setDatastoreReadTimeoutMillis(config.getIntProperty("datanucleus.datastoreReadTimeout"));

        // Set up FetchPlan
        fetchPlan = new FetchPlan(this.getExecutionContext(), clr).setMaxFetchDepth(omf.getIntProperty("datanucleus.maxFetchDepth"));

        // Set up the Level 1 Cache
        initialiseLevel1Cache();

        // Set up the transaction suitable for this ObjectManagerFactory
        if (TransactionType.JTA.toString().equalsIgnoreCase(config.getStringProperty("datanucleus.TransactionType")))
        {
            if (getOMFContext().isJcaMode())
            {
                tx = new JTAJCATransactionImpl(getOMFContext(),getStoreManager(),this);
            }
            else
            {
                tx = new JTATransactionImpl(getOMFContext(),getStoreManager(),this);
            }
        }
        else
        {
            tx = new TransactionImpl(getOMFContext(),getStoreManager(),this.getExecutionContext());
        }
        
        tx.bindTransactionEventListener(new TransactionEventListener()
        {
            public void transactionStarted()
            {
                postBegin();
            }
            
            public void transactionRolledBack()
            {
                postRollback();
            }
            
            public void transactionPreRollBack()
            {
                preRollback();
            }
            
            public void transactionPreCommit()
            {
                preCommit();
            }
            
            public void transactionFlushed()
            {
                //nothing to do
            }
            
            public void transactionEnded()
            {
                //nothing to do
            }
            
            public void transactionCommitted()
            {
                postCommit();
            }
        });
        
        if (omf.hasLevel2Cache())
        {
            txCachedIds = new HashSet();
        }
    }

    /**
     * Method to initialise the L1 cache.
     * @throws NucleusUserException if an error occurs setting up the L1 cache
     */
    protected void initialiseLevel1Cache()
    {
        // Find the L1 cache class name from its plugin name
        String level1Type = omf.getPersistenceConfiguration().getStringProperty("datanucleus.cache.level1.type");
        String level1ClassName = getOMFContext().getPluginManager().getAttributeValueForExtension("org.datanucleus.cache_level1", 
            "name", level1Type, "class-name");
        if (level1ClassName == null)
        {
            // Plugin of this name not found
            throw new NucleusUserException(LOCALISER.msg("003001", level1Type)).setFatal();
        }

        try
        {
            // Create an instance of the L1 Cache
            cache = (Level1Cache)getOMFContext().getPluginManager().createExecutableExtension(
                "org.datanucleus.cache_level1", "name", level1Type, "class-name", null, null);
            if (NucleusLogger.CACHE.isDebugEnabled())
            {
                NucleusLogger.CACHE.debug(LOCALISER.msg("003003", level1Type));
            }
        }
        catch (Exception e)
        {
            // Class name for this L1 cache plugin is not found!
            throw new NucleusUserException(LOCALISER.msg("003002", level1Type, level1ClassName),e).setFatal();
        }
    }

    /**
     * Accessor for whether this ObjectManager is closed.
     * @return Whether this manager is closed.
     */
    public boolean isClosed()
    {
        return closed;
    }

    /**
     * Accessor for the ClassLoaderResolver
     * @return the ClassLoaderResolver
     */
    public ClassLoaderResolver getClassLoaderResolver()
    {
        return clr;
    }

    /**
     * Accessor for the Store Manager.
     * @return StoreManager
     */
    public StoreManager getStoreManager()
    {
        return getOMFContext().getStoreManager();
    }

    /**
     * Accessor for the ObjectManagerFactory to which this manager belongs.
     * @return The OMF
     */
    public ObjectManagerFactoryImpl getObjectManagerFactory()
    {
        return omf;
    }

    /**
     * Accessor for the API adapter.
     * @return API adapter.
     */
    public ApiAdapter getApiAdapter()
    {
        return getOMFContext().getApiAdapter();
    }

    /**
     * Acessor for the current FetchPlan.
     * @return FetchPlan
     */
    public FetchPlan getFetchPlan()
    {
        assertIsOpen();
        return fetchPlan;
    }

    /**
     * Method to return the owner PM/EM object.
     * This currently returns the PersistenceManager. Eventually when we split JPA from JDO it will
     * return the EntityManager for JPA usage.
     * @return The owner manager object
     */
    public Object getOwner()
    {
        return owner;
    }

    /**
     * Gets the context in which this ObjectManager is running
     * @return Returns the context.
     */
    public OMFContext getOMFContext()
    {
        return omf.getOMFContext();
    }

    /**
     * Accessor for the MetaDataManager for this ObjectManager (and its factory).
     * This is used as the interface to MetaData in the ObjectManager/Factory.
     * @return Returns the MetaDataManager.
     */
    public MetaDataManager getMetaDataManager()
    {
        return getOMFContext().getMetaDataManager();
    }

    /**
     * Accessor for the datastore read timeout in milliseconds.
     * @return Datastore read timeout in milliseconds (if specified)
     */
    public Integer getDatastoreReadTimeoutMillis()
    {
        return datastoreReadTimeoutMillis;
    }

    /**
     * Mutator for the datastore read timeout in milliseconds.
     * @param val The timeout
     */
    public void setDatastoreReadTimeoutMillis(Integer val)
    {
        this.datastoreReadTimeoutMillis = val;
    }

    /**
     * Accessor for the datastore write timeout in milliseconds.
     * @return Datastore write timeout in milliseconds (if specified)
     */
    public Integer getDatastoreWriteTimeoutMillis()
    {
        return datastoreWriteTimeoutMillis;
    }

    /**
     * Mutator for the datastore write timeout in milliseconds.
     * @param val The timeout
     */
    public void setDatastoreWriteTimeoutMillis(Integer val)
    {
        this.datastoreWriteTimeoutMillis = val;
    }

    /**
     * Mutator for whether the object manager is multithreaded.
     * @param flag Whether to run multithreaded.
     */
    public void setMultithreaded(boolean flag)
    {
        assertIsOpen();
        this.multithreaded = flag;
    }

    /**
     * Accessor for whether the object manager is multithreaded.
     * @return Whether to run multithreaded.
     */
    public boolean getMultithreaded()
    {
        assertIsOpen();
        return this.multithreaded;
    }

    /**
     * Mutator for whether to detach objects on close of the ObjectManager.
     * <b>This is not suitable for use in JCA mode.</b>
     * @param flag Whether to detach on close.
     */
    public void setDetachOnClose(boolean flag)
    {
        assertIsOpen();
        this.detachOnClose = flag;
    }

    /**
     * Accessor for whether to detach objects on close of the ObjectManager.
     * <b>This is not suitable for use in JCA mode.</b>
     * @return Whether to detach on close.
     */
    public boolean getDetachOnClose()
    {
        assertIsOpen();
        return detachOnClose;
    }

    /**
     * Mutator for whether to detach all objects on commit of the transaction.
     * @param flag Whether to detach all on commit.
     */
    public void setDetachAllOnCommit(boolean flag)
    {
        assertIsOpen();
        this.detachAllOnCommit = flag;
    }

    /**
     * Accessor for whether to detach all objects on commit of the transaction.
     * @return Whether to detach all on commit.
     */
    public boolean getDetachAllOnCommit()
    {
        assertIsOpen();
        return detachAllOnCommit;
    }

   /**
    * Mutator for whether to detach all objects on rollback of the transaction.
    * @param flag Whether to detach all on rollback.
    */
   public void setDetachAllOnRollback(boolean flag)
   {
       assertIsOpen();
       this.detachAllOnRollback = flag;
   }

   /**
    * Accessor for whether to detach all objects on rollback of the transaction.
    * @return Whether to detach all on rollback.
    */
   public boolean getDetachAllOnRollback()
   {
       assertIsOpen();
       return detachAllOnRollback;
   }

    /**
     * Mutator for whether to copy on attaching.
     * @param flag Whether to copy on attaching
     */
    public void setCopyOnAttach(boolean flag)
    {
        assertIsOpen();
        this.copyOnAttach = flag;
    }

    /**
     * Accessor for whether to copy on attaching.
     * @return Whether to copy on attaching
     */
    public boolean getCopyOnAttach()
    {
        assertIsOpen();
        return copyOnAttach;
    }

    /**
     * Mutator for the attach policy.
     * @param policy Attach policy
     */
    public void setAttachPolicy(String policy)
    {
        assertIsOpen();
        this.attachPolicy = policy;
    }

    /**
     * Accessor for the attach policy.
     * @return Attach policy
     */
    public String getAttachPolicy()
    {
        assertIsOpen();
        return attachPolicy;
    }

    /**
     * Mutator for whether to ignore the cache.
     * @param flag Whether to ignore the cache.
     */
    public void setIgnoreCache(boolean flag)
    {
        assertIsOpen();
        this.ignoreCache = flag;
    }

    /**
     * Accessor for whether to ignore the cache.
     * @return Whether to ignore the cache.
     */
    public boolean getIgnoreCache()
    {
        assertIsOpen();
        return ignoreCache;
    }

    /**
     * Whether the datastore operations are delayed until commit/flush. 
     * In optimistic transactions this is automatically enabled. In datastore transactions there is a
     * persistence property to enable it.
     * If we are committing/flushing then will return false since the delay is no longer required.
     * @return true if datastore operations are delayed until commit/flush
     */
    public boolean isDelayDatastoreOperationsEnabled()
    {
        if (flushing || tx.isCommitting())
        {
            // Already sending to the datastore so return false to not confuse things
            return false;
        }

        if (tx.getOptimistic())
        {
            return true;
        }
        else
        {
            return getOMFContext().getPersistenceConfiguration().getBooleanProperty("datanucleus.datastoreTransactionDelayOperations");
        }
    }

    /**
     * Tests whether this persistable object is in the process of being inserted.
     * @param pc the object to verify the status
     * @return true if this instance is inserting.
     */
    public boolean isInserting(Object pc)
    {
        StateManager sm = findStateManager(pc);
        if (sm == null)
        {
            return false;
        }
        return sm.isInserting();
    }

    /**
     * Accessor for the current transaction.
     * @return The transaction
     */
    public Transaction getTransaction()
    {
        assertIsOpen();
        return tx;
    }

    /**
     * Method to enlist the specified StateManager in the current transaction.
     * @param sm The StateManager
     */
    public synchronized void enlistInTransaction(StateManager sm)
    {
        assertActiveTransaction();
        if (NucleusLogger.TRANSACTION.isDebugEnabled())
        {
            NucleusLogger.TRANSACTION.debug(LOCALISER.msg("015017", 
                StringUtils.toJVMIDString(sm.getObject()), sm.getInternalObjectId().toString()));
        }

        if (omf.getBooleanProperty("datanucleus.persistenceByReachabilityAtCommit"))
        {
            if (getApiAdapter().isNew(sm.getObject()))
            {
                // Add this object to the list of new objects in this transaction
                txFlushedNewIds.add(sm.getInternalObjectId());
            }
            else if (getApiAdapter().isPersistent(sm.getObject()) && !getApiAdapter().isDeleted(sm.getObject()))
            {
                // Add this object to the list of known valid persisted objects (unless it is a known new object)
                if (!txFlushedNewIds.contains(sm.getInternalObjectId()))
                {
                    txKnownPersistedIds.add(sm.getInternalObjectId());
                }
            }
        }

        // Add the object to those enlisted
        if (omf.getBooleanProperty("datanucleus.persistenceByReachabilityAtCommit") && !runningPBRAtCommit)
        {
            // Keep a note of the id for use by persistence-by-reachability-at-commit
            txEnlistedIds.add(sm.getInternalObjectId());
        }
        enlistedSMCache.put(sm.getInternalObjectId(), sm);
    }

    /**
     * Method to evict the specified StateManager from the current transaction.
     * @param sm The StateManager
     */
    public synchronized void evictFromTransaction(StateManager sm)
    {
        if (NucleusLogger.TRANSACTION.isDebugEnabled())
        {
            NucleusLogger.TRANSACTION.debug(LOCALISER.msg("015019", 
                StringUtils.toJVMIDString(sm.getObject()), getIdentityAsString(sm.getInternalObjectId())));
        }

        if (enlistedSMCache.remove(sm.getInternalObjectId()) == null)
        {
            //probably because the object was garbage collected
            if (NucleusLogger.TRANSACTION.isDebugEnabled())
            {
                NucleusLogger.TRANSACTION.debug(LOCALISER.msg("010023", 
                    StringUtils.toJVMIDString(sm.getObject()), getIdentityAsString(sm.getInternalObjectId())));
            }
        }
    }

    /**
     * Method to return if an object is enlisted in the current transaction.
     * This is only of use when running "persistence-by-reachability-at-commit"
     * @param id Identity for the object
     * @return Whether it is enlisted in the current transaction
     */
    public boolean isEnlistedInTransaction(Object id)
    {
        if (id == null)
        {
            return false;
        }
        return txEnlistedIds.contains(id);
    }

    /**
     * Convenience method to return the attached object for the specified id if one exists.
     * Returns null if there is no currently enlisted/cached object with the specified id.
     * @param id The id
     * @return The attached object
     */
    public Object getAttachedObjectForId(Object id)
    {
        StateManager sm = enlistedSMCache.get(id);
        if (sm != null)
        {
            return sm.getObject();
        }
        sm = (StateManager)cache.get(id);
        if (sm != null)
        {
            return sm.getObject();
        }
        return null;
    }

    /**
     * Method to add the object managed by the specified StateManager to the (L1) cache.
     * @param sm The StateManager
     */
    public synchronized void addStateManager(StateManager sm)
    {
        // Add to the Level 1 Cache
        putObjectIntoCache(sm);
    }

    /**
     * Method to remove the object managed by the specified StateManager from the cache.
     * @param sm The StateManager
     */
    public synchronized void removeStateManager(StateManager sm)
    {
        Object pc = sm.getObject();

        // Remove from the Level 1 Cache
        removeObjectFromCache(pc, sm.getInternalObjectId());

        // Remove it from any transaction
        enlistedSMCache.remove(sm.getInternalObjectId());
    }

    /**
     * Accessor for the StateManager of an object given the object id.
     * @param id Id of the object.
     * @return The StateManager
     */
    public synchronized StateManager getStateManagerById(Object id)
    {
        assertIsOpen();
        return findStateManager(getObjectFromCache(id));
    }

    /**
     * Method to find the StateManager for an object.
     * @param pc The object we require the StateManager for.
     * @return The StateManager, null if StateManager not found.
     *     See JDO spec for the calling behavior when null is returned
     */
    public synchronized StateManager findStateManager(Object pc)
    {
        StateManager sm = null;
        Object previousLookingFor = objectLookingForStateManager;
        StateManager previousFound = foundStateManager;
        try
        {
            objectLookingForStateManager = pc;
            foundStateManager = null;
            // We call "ObjectManagerHelper.getObjectManager(pc)".
            // This then calls "JDOHelper.getPersistenceManager(pc)".
            // Which calls "StateManager.getPersistenceManager(pc)".
            // That then calls "hereIsStateManager(sm, pc)" which sets "foundStateManager".
            ExecutionContext ec = getApiAdapter().getExecutionContext(pc);
            if (ec != null && this.getExecutionContext() != ec)
            {
                throw new NucleusUserException(LOCALISER.msg("010007", getApiAdapter().getIdForObject(pc)));
            }
            sm = foundStateManager;
        }
        finally
        {
            objectLookingForStateManager = previousLookingFor;
            foundStateManager = previousFound;
        }
        return sm;
    }

    /**
     * Method to add the StateManager for an object to this ObjectManager's list.
     * @param sm The StateManager
     * @param pc The object managed by the StateManager
     */
    public synchronized void hereIsStateManager(StateManager sm, Object pc)
    {
        if (objectLookingForStateManager == pc)
        {
            foundStateManager = sm;
        }
    }

    /**
     * Method to close the Object Manager.
     */
    public synchronized void close()
    {
        if (closed)
        {
            throw new NucleusUserException(LOCALISER.msg("010002"));
        }
        if (tx.isActive())
        {
            throw new TransactionActiveOnCloseException(this);
        }

        // Commit any outstanding non-tx updates TODO Remove this when all mutator operations do it themselves
        nontransactionalUpdateCommit();

        if (detachOnClose)
        {
            // "detach-on-close", detaching all currently cached objects.
            performDetachOnClose();
        }

        ExecutionContext.LifecycleListener[] listener = omf.getOMFContext().getObjectManagerListeners();

        for (int i=0; i<listener.length; i++)
        {
            listener[i].preClose(this.getExecutionContext());
        }

        // Disconnect remaining resources
        disconnectSMCache();
        disconnectLifecycleListener();

        // Reset the Fetch Plan to its DFG setting
        fetchPlan.clearGroups().addGroup(FetchPlan.DEFAULT);
    }

    public void postClose()
    {
        closed = true;
        tx = null;

        if (NucleusLogger.PERSISTENCE.isDebugEnabled())
        {
            NucleusLogger.PERSISTENCE.debug(LOCALISER.msg("010001", this));
        }
    }

    /**
     * Disconnect SM instances, clear cache and reset settings 
     */
    public void disconnectSMCache()
    {
        // Clear out the cache (use separate list since sm.disconnect will remove the object from "cache" so we avoid
        // any ConcurrentModification issues)
        Collection cachedSMsClone = new HashSet(cache.values());
        Iterator iter = cachedSMsClone.iterator();
        while (iter.hasNext())
        {
            StateManager sm = (StateManager) iter.next();
            if (sm != null)
            {
                sm.disconnect();
            }
        }
        cache.clear();
        if (NucleusLogger.CACHE.isDebugEnabled())
        {
            NucleusLogger.CACHE.debug(LOCALISER.msg("003011"));
        }

    }

    /**
     * Method called at the completion of a nontransactional update.
     * Will commit any updates to the datastore.
     */
    protected void nontransactionalUpdateCommit()
    {
        if (!dirtySMs.isEmpty() && tx.getNontransactionalWrite() && !tx.isActive())
        {
            // Make sure the non-tx objects are enlisted so they get lifecycle changes
            Iterator<StateManager> iter = dirtySMs.iterator();
            while (iter.hasNext())
            {
                StateManager sm = iter.next();
                enlistedSMCache.put(sm.getInternalObjectId(), sm);
            }

            // Non-tx write has outstanding updates, so commit them
            NucleusLogger.TRANSACTION.info("Non-tx updates are being committed to the datastore");
            tx.begin();
            tx.commit();
        }
    }

    // ----------------------------- Lifecycle Methods ------------------------------------

    /**
     * Internal method to evict an object from L1 cache.
     * @param obj The object
     * @throws NucleusException if an error occurs evicting the object
     */
    public void evictObject(Object obj)
    {
        if (obj == null)
        {
            return;
        }

        try
        {
            clr.setPrimary(obj.getClass().getClassLoader());
            assertClassPersistable(obj.getClass());
            assertNotDetached(obj);

            // we do not directly remove from cache level 1 here. The cache level 1 will be evicted 
            // automatically on garbage collection, if the object can be evicted. it means not all
            // jdo states allows the object to be evicted.
            StateManager sm = findStateManager(obj);
            if (sm == null)
            {
                throw new NucleusUserException(LOCALISER.msg("010007", getApiAdapter().getIdForObject(obj)));
            }
            sm.evict();
        }
        finally
        {
            clr.unsetPrimary();
        }
    }

    /**
     * Method to evict all objects of the specified type (and optionaly its subclasses).
     * @param cls Type of persistable object
     * @param subclasses Whether to include subclasses
     */
    public void evictObjects(Class cls, boolean subclasses)
    {
        assertIsOpen();

        ArrayList stateManagersToEvict = new ArrayList();
        stateManagersToEvict.addAll(cache.values());
        Iterator smIter = stateManagersToEvict.iterator();
        while (smIter.hasNext())
        {
            StateManager sm = (StateManager)smIter.next();
            Object pc = sm.getObject();
            boolean evict = false;
            if (!subclasses && pc.getClass() == cls)
            {
                evict = true;
            }
            else if (subclasses && cls.isAssignableFrom(pc.getClass()))
            {
                evict = true;
            }

            if (evict)
            {
                sm.evict();
                removeObjectFromCache(pc, getApiAdapter().getIdForObject(pc));
            }
        }
    }

    /**
     * Method to evict all current objects from L1 cache.
     */
    public synchronized void evictAllObjects()
    {
        assertIsOpen();

        // All persistent non-transactional instances should be evicted here, but not yet supported
        ArrayList stateManagersToEvict = new ArrayList();
        stateManagersToEvict.addAll(cache.values());

        // Evict StateManagers and remove objects from cache
        // Performed in separate loop to avoid ConcurrentModificationException
        Iterator smIter = stateManagersToEvict.iterator();
        while (smIter.hasNext())
        {
            StateManager sm = (StateManager)smIter.next();
            Object pc = sm.getObject();
            sm.evict();

            // Evict from L1
            removeObjectFromCache(pc, getApiAdapter().getIdForObject(pc));
        }
    }

    /**
     * Method to do a refresh of an object, updating it from its
     * datastore representation. Also updates the object in the L1/L2 caches.
     * @param obj The Object
     */
    public void refreshObject(Object obj)
    {
        if (obj == null)
        {
            return;
        }
        try
        {
            clr.setPrimary(obj.getClass().getClassLoader());
            assertClassPersistable(obj.getClass());
            assertNotDetached(obj);

            StateManager sm = findStateManager(obj);
            if (sm == null)
            {
                throw new NucleusUserException(LOCALISER.msg("010007", getApiAdapter().getIdForObject(obj)));
            }

            if (getApiAdapter().isPersistent(obj) && sm.isWaitingToBeFlushedToDatastore())
            {
                // Persistent but not yet flushed so nothing to "refresh" from!
                return;
            }

            sm.refresh();
        }
        finally
        {
            clr.unsetPrimary();
        }
    }

    /**
     * Method to do a refresh of all objects.
     * @throws NucleusUserException thrown if instances could not be refreshed.
     */
    public synchronized void refreshAllObjects()
    {
        assertIsOpen();

        Set toRefresh = new HashSet();
        toRefresh.addAll(enlistedSMCache.values());
        toRefresh.addAll(dirtySMs);
        toRefresh.addAll(indirectDirtySMs);
        if (!tx.isActive())
        {
            toRefresh.addAll(cache.values());
        }

        List failures = null;
        Iterator iter = toRefresh.iterator();
        while (iter.hasNext())
        {
            try
            {
                Object obj = iter.next();
                StateManager sm;
                if (getApiAdapter().isPersistable(obj))
                {
                    sm = findStateManager(obj);
                }
                else
                {
                    sm = (StateManager) obj;
                }
                sm.refresh();
            }
            catch (RuntimeException e)
            {
                if (failures == null)
                {
                    failures = new ArrayList();
                }
                failures.add(e);
            }
        }
        if (failures != null && !failures.isEmpty())
        {
            throw new NucleusUserException(LOCALISER.msg("010037"), (Exception[]) failures.toArray(new Exception[failures.size()]));
        }
    }

    /**
     * Method to retrieve an object.
     * @param obj The object
     * @param fgOnly Whether to retrieve the current fetch group fields only
     */
    public void retrieveObject(Object obj, boolean fgOnly)
    {
        if (obj == null)
        {
            return;
        }
        try
        {
            clr.setPrimary(obj.getClass().getClassLoader());
            assertClassPersistable(obj.getClass());
            assertNotDetached(obj);

            StateManager sm = findStateManager(obj);
            if (sm == null)
            {
                throw new NucleusUserException(LOCALISER.msg("010007", getApiAdapter().getIdForObject(obj)));
            }
            sm.retrieve(fgOnly);
        }
        finally
        {
            clr.unsetPrimary();
        }
    }

    /**
     * Context info for a particular thread. Can be used for storing state information for the current
     * thread where we don't want to pass it through large numbers of method calls (e.g persistence by
     * reachability) where such argument passing would damage the structure of DataNucleus.
     */
    class ThreadContextInfo
    {
      int referenceCounter = 0;

        /** Map of attached PC object keyed by the id. Present when performing a persist operation. */
        HashMap attachedPCById = null;
    }

    /**
     * Accessor for the thread context information, for the current thread.
     * If the current thread is not present, will add an info context for it.
     * <p>
     * You must call {@link #releaseThreadContextInfo()} when you don't need it anymore,
     * since we use reference counting. Use a try...finally-block for this purpose.
     * </p>
     *
     * @return The thread context information
     * @see #getThreadContextInfo()
     */
    protected ThreadContextInfo acquireThreadContextInfo()
    {
        ThreadContextInfo threadInfo = (ThreadContextInfo) contextInfoThreadLocal.get();
        ++threadInfo.referenceCounter;
        return threadInfo;
    }

    /**
     * Get the current ThreadContextInfo assigned to the current thread without changing the
     * reference counter.
     * @return the thread context information
     * @see #acquireThreadContextInfo()
     */
    protected ThreadContextInfo getThreadContextInfo()
    {
      return (ThreadContextInfo) contextInfoThreadLocal.get();
    }

    /**
     * Method to remove the current thread context info for the current thread, after
     * the reference counter reached 0. This method decrements a reference counter (per thread), that
     * is incremented by {@link #acquireThreadContextInfo()}.
     *
     * @see #acquireThreadContextInfo()
     */
    protected void releaseThreadContextInfo()
    {
      ThreadContextInfo threadInfo = (ThreadContextInfo) contextInfoThreadLocal.get();
      if (--threadInfo.referenceCounter <= 0) // might be -1, if acquireThreadContextInfo was not called. shall we throw an exception in this case?
      {
          threadInfo.referenceCounter = 0; // just to be 100% sure, we never have a negative reference counter.

          if (threadInfo.attachedPCById != null)
              threadInfo.attachedPCById.clear();

        threadInfo.attachedPCById = null;
        contextInfoThreadLocal.remove();
      }
    }

    /**
     * Method to make an object persistent.
     * NOT to be called by internal DataNucleus methods. Only callable by external APIs (JDO/JPA).
     * @param obj The object
     * @return The persisted object
     * @throws NucleusUserException if the object is managed by a different manager
     */
    public Object persistObject(Object obj)
    {
        assertIsOpen();
        assertWritable();
        if (obj == null)
        {
            return null;
        }

        // Make sure we have attachedPC lookup info initialised in case we need to attach objects multiple times
        ThreadContextInfo threadInfo = acquireThreadContextInfo();
        try
        {
            if (threadInfo.attachedPCById == null)
            {
                threadInfo.attachedPCById = new HashMap();
            }

            boolean detached = getApiAdapter().isDetached(obj);

            // Persist the object
            Object persistedPc = null;
            if (this.multithreaded)
            {
                synchronized (obj)
                {
                    persistedPc = persistObjectInternal(obj, null, null, -1, StateManager.PC);
                }
            }
            else
            {
                persistedPc = persistObjectInternal(obj, null, null, -1, StateManager.PC);
            }

            // If using reachability at commit and appropriate save it for reachability checks when we commit
            StateManager sm = findStateManager(persistedPc);
            if (sm != null)
            {
                if (indirectDirtySMs.contains(sm))
                {
                    dirtySMs.add(sm);
                    indirectDirtySMs.remove(sm);
                }
                else if (!dirtySMs.contains(sm))
                {
                    dirtySMs.add(sm);
                    if (txCachedIds != null)
                    {
                        txCachedIds.add(sm.getInternalObjectId());
                    }
                }

                if (omf.getBooleanProperty("datanucleus.persistenceByReachabilityAtCommit"))
                {
                    if (detached || getApiAdapter().isNew(persistedPc))
                    {
                        txKnownPersistedIds.add(sm.getInternalObjectId());
                    }
                }
            }

            return persistedPc;
        }
        finally
        {
            // Commit any non-tx changes
            nontransactionalUpdateCommit();

            // Deallocate attached PC lookup
            releaseThreadContextInfo();
        }
    }

    /**
     * Method to persist an array of objects to the datastore.
     * @param objs The objects to persist
     * @return The persisted objects
     * @throws NucleusUserException Thrown if an error occurs during the persist process.
     *     Any exception could have several nested exceptions for each failed object persist
     */
    public Object[] persistObjects(Object[] objs)
    {
        if (objs == null)
        {
            return null;
        }

        Object[] persistedObjs = new Object[objs.length];
        try
        {
            getStoreManager().getPersistenceHandler().batchStart(executionContext);
            ArrayList failures = null;
            for (int i=0;i<objs.length;i++)
            {
                try
                {
                    persistedObjs[i] = persistObject(objs[i]);
                }
                catch (RuntimeException e)
                {
                    if (failures == null)
                    {
                        failures = new ArrayList();
                    }
                    failures.add(e);
                }
            }
            if (failures != null && !failures.isEmpty())
            {
                throw new NucleusUserException(LOCALISER.msg("010039"), 
                    (Exception[]) failures.toArray(new Exception[failures.size()]));
            }
        }
        finally
        {
            getStoreManager().getPersistenceHandler().batchEnd(executionContext);
        }
        return persistedObjs;
    }

    /**
     * Method to make an object persistent which should be called from internal calls only.
     * All PM/EM calls should go via persistObject(Object obj).
     * @param obj The object
     * @param preInsertChanges Any changes to make before inserting
     * @param ownerSM StateManager of the owner when embedded
     * @param ownerFieldNum Field number in the owner where this is embedded (or -1 if not embedded)
     * @param objectType Type of object (see org.datanucleus.StateManager, e.g StateManager.PC)
     * @return The persisted object
     * @throws NucleusUserException if the object is managed by a different manager
     */
    public Object persistObjectInternal(Object obj, FieldValues preInsertChanges, 
            StateManager ownerSM, int ownerFieldNum, int objectType)
    {
        if (obj == null)
        {
            return null;
        }
        assertIsOpen();
        assertWritable();
        // TODO Support embeddedOwner/objectType, so we can add StateManager for embedded objects here

        Object id = null; // Id of the object that was persisted during this process (if any)
        try
        {
            clr.setPrimary(obj.getClass().getClassLoader());
            assertClassPersistable(obj.getClass());
            if (!getApiAdapter().isDetached(obj) && NucleusLogger.PERSISTENCE.isDebugEnabled())
            {
                NucleusLogger.PERSISTENCE.debug(LOCALISER.msg("010015", StringUtils.toJVMIDString(obj)));
            }
            ExecutionContext ec = getApiAdapter().getExecutionContext(obj);
            if (ec != null && ec != this.getExecutionContext())
            {
                // Object managed by a different manager
                throw new NucleusUserException(LOCALISER.msg("010007", obj));
            }

            Object persistedPc = obj; // Persisted object is the passed in pc (unless being attached as a copy)
            if (getApiAdapter().isDetached(obj))
            {
                // Detached : attach it
                assertDetachable(obj);
                if (copyOnAttach)
                {
                    // Attach a copy and return the copy
                    persistedPc = attachObjectCopy(obj, getApiAdapter().getIdForObject(obj) == null);
                }
                else
                {
                    // Attach the object
                    attachObject(obj, getApiAdapter().getIdForObject(obj) == null);
                    persistedPc = obj;
                }
            }
            else if (getApiAdapter().isTransactional(obj) && !getApiAdapter().isPersistent(obj))
            {
                // TransientTransactional : persist it
                StateManager sm = findStateManager(obj);
                if (sm == null)
                {
                    throw new NucleusUserException(LOCALISER.msg("010007", getApiAdapter().getIdForObject(obj)));
                }
                sm.makePersistentTransactionalTransient();
            }
            else if (!getApiAdapter().isPersistent(obj))
            {
                // Transient : persist it
                StateManager sm = findStateManager(obj);
                if (sm == null)
                {
                    if (objectType != StateManager.PC && ownerSM != null)
                    {
                        // SCO object
                        sm = StateManagerFactory.newStateManagerForEmbedded(this.getExecutionContext(), obj, false);
                        sm.addEmbeddedOwner(ownerSM, ownerFieldNum);
                        sm.setPcObjectType(objectType);
                        sm.makePersistent();
                        id = sm.getInternalObjectId();
                    }
                    else
                    {
                        // FCO object
                        sm = StateManagerFactory.newStateManagerForPersistentNew(this.getExecutionContext(), obj, preInsertChanges);
                        sm.makePersistent();
                        id = sm.getInternalObjectId();
                    }
                }
                else
                {
                    if (sm.getReferencedPC() == null)
                    {
                        // Persist it
                        sm.makePersistent();
                        id = sm.getInternalObjectId();
                    }
                    else
                    {
                        // Being attached, so use the attached object
                        persistedPc = sm.getReferencedPC();
                    }
                }
            }
            else if (getApiAdapter().isPersistent(obj) && getApiAdapter().getIdForObject(obj) == null)
            {
                // Embedded/Serialised : have SM but no identity, allow persist in own right
                // Should we be making a copy of the object here ?
                    StateManager sm = findStateManager(obj);
                    sm.makePersistent();
                    id = sm.getInternalObjectId();
            }
            else if (getApiAdapter().isDeleted(obj))
            {
                // Deleted : (re)-persist it (permitted in JPA, but not JDO - see StateManager)
                StateManager sm = findStateManager(obj);
                sm.makePersistent();
                id = sm.getInternalObjectId();
            }
            else
            {
                if (getApiAdapter().isPersistent(obj) &&
                    getApiAdapter().isTransactional(obj) &&
                    getApiAdapter().isDirty(obj) &&
                    isDelayDatastoreOperationsEnabled())
                {
                    // Object provisionally persistent (but not in datastore) so re-run reachability maybe
                    StateManager sm = findStateManager(obj);
                    sm.makePersistent();
                    id = sm.getInternalObjectId();
                }
            }

            if (id != null && txCachedIds != null)
            {
                txCachedIds.add(id);
            }
            return persistedPc;
        }
        finally
        {
            clr.unsetPrimary();
        }
    }

    /**
     * Method to delete an object from the datastore.
     * NOT to be called by internal methods. Only callable by external APIs (JDO/JPA).
     * @param obj The object
     */
    public void deleteObject(Object obj)
    {
        StateManager sm = findStateManager(obj);
        if (sm != null)
        {
            // Add the object to the relevant list of dirty StateManagers
            if (indirectDirtySMs.contains(sm))
            {
                // Object is dirty indirectly, but now user-requested so move to direct list of dirty objects
                indirectDirtySMs.remove(sm);
                dirtySMs.add(sm);
            }
            else if (!dirtySMs.contains(sm))
            {
                dirtySMs.add(sm);
                if (txCachedIds != null)
                {
                    txCachedIds.add(sm.getInternalObjectId());
                }
            }
        }

        // Delete the object
        if (this.multithreaded)
        {
            synchronized (obj)
            {
                deleteObjectInternal(obj);
            }
        }
        else
        {
            deleteObjectInternal(obj);
        }

        if (omf.getBooleanProperty("datanucleus.persistenceByReachabilityAtCommit"))
        {
            if (sm != null)
            {
                if (getApiAdapter().isDeleted(obj))
                {
                    txKnownDeletedIds.add(sm.getInternalObjectId());
                }
            }
        }

        // Commit any non-tx changes
        nontransactionalUpdateCommit();
    }

    /**
     * Method to delete an object from persistence which should be called from internal calls only.
     * All PM/EM calls should go via deleteObject(Object obj).
     * @param obj Object to delete
     */
    public void deleteObjectInternal(Object obj)
    {
        if (obj == null)
        {
            return;
        }
        assertIsOpen();
        assertWritable();

        try
        {
            clr.setPrimary(obj.getClass().getClassLoader());
            assertClassPersistable(obj.getClass());

            Object pc = obj;
            if (getApiAdapter().isDetached(obj))
            {
                // Load up the attached instance with this identity
                pc = findObject(getApiAdapter().getIdForObject(obj), true, true, null);
            }

            if (NucleusLogger.PERSISTENCE.isDebugEnabled())
            {
                NucleusLogger.PERSISTENCE.debug(LOCALISER.msg("010019", StringUtils.toJVMIDString(pc)));
            }

            // Check that the object is valid for deleting
            if (getApiAdapter().getName().equals("JDO"))
            {
                // JDO doesn't allow deletion of transient
                if (!getApiAdapter().isPersistent(pc) && !getApiAdapter().isTransactional(pc))
                {
                    throw new NucleusUserException(LOCALISER.msg("010020"));
                }
                else if (!getApiAdapter().isPersistent(pc) && getApiAdapter().isTransactional(pc))
                {
                    throw new NucleusUserException(LOCALISER.msg("010021"));
                }
            }

            // Delete it
            StateManager sm = findStateManager(pc);
            if (sm == null)
            {
                if (!getApiAdapter().allowDeleteOfNonPersistentObject())
                {
                    // Not permitted by the API
                    throw new NucleusUserException(LOCALISER.msg("010007", getApiAdapter().getIdForObject(pc)));
                }

                // Put StateManager around object so it is P_NEW (unpersisted), then P_NEW_DELETED soon after
                sm = StateManagerFactory.newStateManagerForPNewToBeDeleted(this.getExecutionContext(), pc);
            }

            if (txCachedIds != null)
            {
                // Mark for L2 cache update
                txCachedIds.add(sm.getInternalObjectId());
            }

            // Move to deleted state
            sm.deletePersistent();
        }
        finally
        {
            clr.unsetPrimary();
        }
    }

    /**
     * Method to delete an array of objects from the datastore.
     * @param objs The objects
     * @throws NucleusUserException Thrown if an error occurs during the deletion process.
     *     Any exception could have several nested exceptions for each failed object deletion
     */
    public void deleteObjects(Object[] objs)
    {
        if (objs == null)
        {
            return;
        }

        try
        {
            getStoreManager().getPersistenceHandler().batchStart(executionContext);

            ArrayList failures = null;
            for (int i=0;i<objs.length;i++)
            {
                try
                {
                    deleteObject(objs[i]);
                }
                catch (RuntimeException e)
                {
                    if (failures == null)
                    {
                        failures = new ArrayList();
                    }
                    failures.add(e);
                }
            }
            if (failures != null && !failures.isEmpty())
            {
                throw new NucleusUserException(LOCALISER.msg("010040"), 
                    (Exception[]) failures.toArray(new Exception[failures.size()]));
            }
        }
        finally
        {
            getStoreManager().getPersistenceHandler().batchEnd(executionContext);
        }
    }

    /**
     * Method to migrate an object to transient state.
     * @param obj The object
     * @param state Object containing the state of the fetch plan process (if any)
     * @throws NucleusException When an error occurs in making the object transient
     */
    public synchronized void makeObjectTransient(Object obj, FetchPlanState state)
    {
        if (obj == null)
        {
            return;
        }

        try
        {
            clr.setPrimary(obj.getClass().getClassLoader());
            assertClassPersistable(obj.getClass());
            assertNotDetached(obj);

            if (NucleusLogger.PERSISTENCE.isDebugEnabled())
            {
                NucleusLogger.PERSISTENCE.debug(LOCALISER.msg("010022", StringUtils.toJVMIDString(obj)));
            }

            if (getApiAdapter().isPersistent(obj))
            {
                StateManager sm = findStateManager(obj);
                sm.makeTransient(state);
            }
        }
        finally
        {
            clr.unsetPrimary();
        }
    }

    /**
     * Method to make an object transactional.
     * @param obj The object
     * @throws NucleusException Thrown when an error occurs
     */
    public void makeObjectTransactional(Object obj)
    {
        if (obj == null)
        {
            return;
        }
        try
        {
            clr.setPrimary(obj.getClass().getClassLoader());
            assertClassPersistable(obj.getClass());
            assertNotDetached(obj);

            if (getApiAdapter().isPersistent(obj))
            {
                assertActiveTransaction();
            }
            StateManager sm = findStateManager(obj);
            if (sm == null)
            {
                sm = StateManagerFactory.newStateManagerForTransactionalTransient(this.getExecutionContext(), obj);
            }
            sm.makeTransactional();
        }
        finally
        {
            clr.unsetPrimary();
        }
    }

    /**
     * Method to make an object nontransactional.
     * @param obj The object
     */
    public void makeObjectNontransactional(Object obj)
    {
        if (obj == null)
        {
            return;
        }
        try
        {
            clr.setPrimary(obj.getClass().getClassLoader());
            assertClassPersistable(obj.getClass());
            if (!getApiAdapter().isPersistent(obj) && getApiAdapter().isTransactional(obj) && getApiAdapter().isDirty(obj))
            {
                throw new NucleusUserException(LOCALISER.msg("010024"));
            }

            StateManager sm = findStateManager(obj);
            sm.makeNontransactional();
        }
        finally
        {
            clr.unsetPrimary();
        }
    }
    
    /**
     * Method to attach a persistent detached object.
     * If a different object with the same identity as this object exists in the L1 cache then an exception
     * will be thrown.
     * @param pc The persistable object
     * @param sco Whether the PC object is stored without an identity (embedded/serialised)
     */
    public synchronized void attachObject(Object pc, boolean sco)
    {
        assertIsOpen();
        assertClassPersistable(pc.getClass());

        ApiAdapter api = getApiAdapter();
        Object id = api.getIdForObject(pc);
        if (id != null && isInserting(pc))
        {
            // Object is being inserted in this transaction so just return
            return;
        }
        else if (id == null && !sco)
        {
            // Transient object so needs persisting
            persistObjectInternal(pc, null, null, -1, StateManager.PC);
            return;
        }

        if (api.isDetached(pc))
        {
            // Detached, so migrate to attached
            StateManager l1CachedSM = (StateManager)cache.get(id);
            if (l1CachedSM != null && l1CachedSM.getObject() != pc)
            {
                // attached object with the same id already present in the L1 cache so cannot attach in-situ
                throw new NucleusUserException(LOCALISER.msg("010017",
                    StringUtils.toJVMIDString(pc)));
            }

            if (NucleusLogger.PERSISTENCE.isDebugEnabled())
            {
                NucleusLogger.PERSISTENCE.debug(LOCALISER.msg("010016", 
                    StringUtils.toJVMIDString(pc)));
            }
            StateManager sm = 
                StateManagerFactory.newStateManagerForDetached(this.getExecutionContext(), pc, id, api.getVersionForObject(pc));
            sm.attach(sco);
        }
        else
        {
            // Not detached so can't attach it. Just return
            return;
        }
    }

    /**
     * Method to attach a persistent detached object returning an attached copy of the object.
     * If the object is of class that is not detachable, a ClassNotDetachableException will be thrown.
     * @param pc The object
     * @param sco Whether it has no identity (second-class object)
     * @return The attached object
     */
    public synchronized Object attachObjectCopy(Object pc, boolean sco)
    {
        assertIsOpen();
        assertClassPersistable(pc.getClass());
        assertDetachable(pc);

        ApiAdapter api = getApiAdapter();
        Object id = api.getIdForObject(pc);
        if (id != null && isInserting(pc))
        {
            // Object is being inserted in this transaction
            return pc;
        }
        else if (id == null && !sco)
        {
            // Object was not persisted before so persist it
            return persistObjectInternal(pc, null, null, -1, StateManager.PC);
        }
        else if (api.isPersistent(pc))
        {
            // Already persistent hence can't be attached
            return pc;
        }

        // Object should exist in this datastore now
        Object pcTarget = null;
        if (sco)
        {
            // SCO PC (embedded/serialised)
            boolean detached = getApiAdapter().isDetached(pc);
            StateManager smTarget = StateManagerFactory.newStateManagerForEmbedded(this.getExecutionContext(), pc, true);
            pcTarget = smTarget.getObject();
            if (detached)
            {
                // If the object is detached, re-attach it
                if (NucleusLogger.PERSISTENCE.isDebugEnabled())
                {
                    NucleusLogger.PERSISTENCE.debug(LOCALISER.msg("010018", 
                        StringUtils.toJVMIDString(pc), StringUtils.toJVMIDString(pcTarget)));
                }
                smTarget.attachCopy(pc, sco);
            }
        }
        else
        {
            // FCO PC
            boolean detached = getApiAdapter().isDetached(pc);
            pcTarget = findObject(id, false, false, pc.getClass().getName());
            if (detached)
            {
                Object obj = null;
                HashMap attachedPCById = getThreadContextInfo().attachedPCById; // For the current thread
                if (attachedPCById != null) // Only used by persistObject process
                {
                    obj = attachedPCById.get(getApiAdapter().getIdForObject(pc));
                }
                if (obj != null)
                {
                    pcTarget = obj;
                }
                else
                {
                    // If the object is detached, re-attach it
                    if (NucleusLogger.PERSISTENCE.isDebugEnabled())
                    {
                        NucleusLogger.PERSISTENCE.debug(LOCALISER.msg("010018", 
                            StringUtils.toJVMIDString(pc), StringUtils.toJVMIDString(pcTarget)));
                    }
                    findStateManager(pcTarget).attachCopy(pc, sco);

                    // Save the detached-attached PCs for later reference
                    if (attachedPCById != null) // Only used by persistObject process
                    {
                        attachedPCById.put(getApiAdapter().getIdForObject(pc), pcTarget);
                    }
                }
            }
        }

        return pcTarget;
    }

    /**
     * Method to detach a persistent object without making a copy. Note that 
     * also all the objects which are refered to from this object are detached.
     * If the object is of class that is not detachable a ClassNotDetachableException
     * will be thrown. If the object is not persistent a JDOUserException is thrown.
     * <B>For internal use only</B>
     * @param obj The object
     * @param state State for the detachment process
     */
    public synchronized void detachObject(Object obj, FetchPlanState state)
    {
        assertIsOpen();
        assertClassPersistable(obj.getClass());
        assertDetachable(obj); // Is this required?

        if (getApiAdapter().isDetached(obj))
        {
            return;
        }

        if (!getApiAdapter().isPersistent(obj))
        {
            // Transient object passed so persist it before thinking about detaching
            if (tx.isActive())
            {
                persistObjectInternal(obj, null, null, -1, StateManager.PC);
            }
        }

        StateManager sm = findStateManager(obj);
        if (sm == null)
        {
            throw new NucleusUserException(LOCALISER.msg("010007", getApiAdapter().getIdForObject(obj)));
        }
        sm.detach(state);
    }

    /**
     * Detach a copy of the passed persistent object using the provided detach state.
     * If the object is of class that is not detachable it will be detached as transient.
     * If it is not yet persistent it will be first persisted.
     * @param pc The object
     * @param state State for the detachment process
     * @return The detached object
     */
    public Object detachObjectCopy(Object pc, FetchPlanState state)
    {
        assertIsOpen();
        assertClassPersistable(pc.getClass());

        Object thePC = pc;
        try
        {
            clr.setPrimary(pc.getClass().getClassLoader());
            if (!getApiAdapter().isPersistent(pc) && !getApiAdapter().isDetached(pc))
            {
                // Transient object passed so persist it before thinking about detaching
                if (tx.isActive())
                {
                    thePC = persistObjectInternal(pc, null, null, -1, StateManager.PC);
                }
                else
                {
                    // JDO2 [12.6.8] "If a detachCopy method is called outside an active transaction, the reachability algorithm
                    // will not be run; if any transient instances are reachable via persistent fields, a JDOUserException is thrown 
                    // for each persistent instance containing such fields.
                    throw new NucleusUserException(LOCALISER.msg("010014"));
                }
            }

            if (getApiAdapter().isDetached(thePC))
            {
                // Passing in a detached (dirty or clean) instance, so get a persistent copy to detach
                thePC = findObject(getApiAdapter().getIdForObject(thePC), false, true, null);
            }

            StateManager sm = findStateManager(thePC);
            if (sm == null)
            {
                throw new NucleusUserException(LOCALISER.msg("010007", getApiAdapter().getIdForObject(thePC)));
            }

            return sm.detachCopy(state);
        }
        finally
        {
            clr.unsetPrimary();
        }
    }

    /**
     * Method to detach all objects in the ObjectManager.
     * Detaches all objects enlisted as well as all objects in the L1 cache.
     * Of particular use with JPA when doing a clear of the persistence context.
     */
    public void detachAll()
    {
        Collection<StateManager> smsToDetach = new HashSet();
        smsToDetach.addAll(this.enlistedSMCache.values());
        smsToDetach.addAll(this.cache.values());
        FetchPlanState fps = new FetchPlanState();
        Iterator<StateManager> iter = smsToDetach.iterator();
        while (iter.hasNext())
        {
            iter.next().detach(fps);
        }
    }

    // ----------------------------- New Instances ----------------------------------

    /**
     * Method to generate an instance of an interface, abstract class, or concrete PC class.
     * @param cls The class of the interface or abstract class, or concrete class defined in MetaData
     * @return The instance of this type
     */
    public Object newInstance(Class cls)
    {
        assertIsOpen();

        if (getApiAdapter().isPersistable(cls) && !Modifier.isAbstract(cls.getModifiers()))
        {
            // Concrete PC class so instantiate here
            try
            {
                return cls.newInstance();
            }
            catch (IllegalAccessException iae)
            {
                throw new NucleusUserException(iae.toString(), iae);
            }
            catch (InstantiationException ie)
            {
                throw new NucleusUserException(ie.toString(), ie);
            }
        }

        // Use ImplementationCreator
        assertHasImplementationCreator();
        return getOMFContext().getImplementationCreator().newInstance(cls, clr);
    }

    // ----------------------------- Object Retrieval by Id ----------------------------------

    /**
     * Method to return if the specified object exists in the datastore.
     * @param obj The (persistable) object
     * @return Whether it exists
     */
    public boolean exists(Object obj)
    {
        if (obj == null)
        {
            return false;
        }

        Object id = getApiAdapter().getIdForObject(obj);
        if (id == null)
        {
            return false;
        }

        try
        {
            findObject(id, true, false, obj.getClass().getName());
        }
        catch (NucleusObjectNotFoundException onfe)
        {
            return false;
        }

        return true;
    }

    /**
     * Accessor for the currently managed objects for the current transaction.
     * If the transaction is not active this returns null.
     * @return Collection of managed objects enlisted in the current transaction
     */
    public Set getManagedObjects()
    {
        if (!tx.isActive())
        {
            return null;
        }

        Set objs = new HashSet();
        Collection sms = enlistedSMCache.values();
        Iterator<StateManager> smsIter = sms.iterator();
        while (smsIter.hasNext())
        {
            StateManager sm = smsIter.next();
            objs.add(sm.getObject());
        }
        return objs;
    }

    /**
     * Accessor for the currently managed objects for the current transaction.
     * If the transaction is not active this returns null.
     * @param classes Classes that we want the enlisted objects for
     * @return Collection of managed objects enlisted in the current transaction
     */
    public Set getManagedObjects(Class[] classes)
    {
        if (!tx.isActive())
        {
            return null;
        }

        Set objs = new HashSet();
        Collection sms = enlistedSMCache.values();
        Iterator<StateManager> smsIter = sms.iterator();
        while (smsIter.hasNext())
        {
            StateManager sm = smsIter.next();
            for (int i=0;i<classes.length;i++)
            {
                if (classes[i] == sm.getObject().getClass())
                {
                    objs.add(sm.getObject());
                    break;
                }
            }
        }
        return objs;
    }

    /**
     * Accessor for the currently managed objects for the current transaction.
     * If the transaction is not active this returns null.
     * @param states States that we want the enlisted objects for
     * @return Collection of managed objects enlisted in the current transaction
     */
    public Set getManagedObjects(String[] states)
    {
        if (!tx.isActive())
        {
            return null;
        }

        Set objs = new HashSet();
        Collection sms = enlistedSMCache.values();
        Iterator<StateManager> smsIter = sms.iterator();
        while (smsIter.hasNext())
        {
            StateManager sm = smsIter.next();
            for (int i=0;i<states.length;i++)
            {
                if (getApiAdapter().getObjectState(sm.getObject()).equals(states[i]))
                {
                    objs.add(sm.getObject());
                    break;
                }
            }
        }
        return objs;
    }

    /**
     * Accessor for the currently managed objects for the current transaction.
     * If the transaction is not active this returns null.
     * @param states States that we want the enlisted objects for
     * @param classes Classes that we want the enlisted objects for
     * @return Collection of managed objects enlisted in the current transaction
     */
    public Set getManagedObjects(String[] states, Class[] classes)
    {
        if (!tx.isActive())
        {
            return null;
        }

        Set objs = new HashSet();
        Collection sms = enlistedSMCache.values();
        Iterator<StateManager> smsIter = sms.iterator();
        while (smsIter.hasNext())
        {
            boolean matches = false;
            StateManager sm = smsIter.next();
            for (int i=0;i<states.length;i++)
            {
                if (getApiAdapter().getObjectState(sm.getObject()).equals(states[i]))
                {
                    for (int j=0;i<classes.length;i++)
                    {
                        if (classes[j] == sm.getObject().getClass())
                        {
                            matches = true;
                            objs.add(sm.getObject());
                            break;
                        }
                    }
                }
                if (matches)
                {
                    break;
                }
            }
        }
        return objs;
    }
    
    /**
     * Accessor for the StateManager of an object given the object AID.
     * @param pcClass The class of the PC object
     * @param fv The field values to be loaded
     * @param ignoreCache true if it must ignore the cache
     * @param checkInheritance Whether look to the database to determine which
     * class this object is. This parameter is a hint. Set false, if it's
     * already determined the correct pcClass for this pc "object" in a certain
     * level in the hierarchy. Set to true and it will look to the database.
     * @return Object
     */
    public synchronized Object findObjectUsingAID(Class pcClass, FieldValues fv, boolean ignoreCache, boolean checkInheritance)
    {
        assertIsOpen();

        // Create StateManager to generate an identity 
        // TODO Provide a more efficient way of doing this. It creates a PC object just to get the id!
        StateManager sm = StateManagerFactory.newStateManagerForHollowPopulatedAppId(this.getExecutionContext(), pcClass, fv);
        if (!ignoreCache)
        {
            // Check the cache
            Object oid = sm.getInternalObjectId();
            Object pc = getObjectFromCache(oid);
            if (pc != null)
            {
                sm = findStateManager(pc);
                sm.loadFieldValues(fv); // Load the values retrieved by the query
                return pc;
            }
            if (checkInheritance)
            {
                ApiAdapter api = getApiAdapter();
                if (oid instanceof OID || api.isSingleFieldIdentity(oid))
                {
                    // Check if this id for any known subclasses is in the cache to save searching
                    String[] subclasses = getMetaDataManager().getSubclassesForClass(pcClass.getName(), true);
                    if (subclasses != null)
                    {
                        for (int i=0;i<subclasses.length;i++)
                        {
                            if (api.isDatastoreIdentity(oid))
                            {
                                oid = OIDFactory.getInstance(getOMFContext(), subclasses[i], ((OID)oid).getKeyValue());
                            }
                            else if (api.isSingleFieldIdentity(oid))
                            {
                                oid = api.getNewSingleFieldIdentity(oid.getClass(), clr.classForName(subclasses[i]), 
                                    api.getTargetKeyForSingleFieldIdentity(oid));
                            }
                            pc = getObjectFromCache(oid);
                            if (pc != null)
                            {
                                sm = findStateManager(pc);
                                sm.loadFieldValues(fv); // Load the values retrieved by the query
                                putObjectIntoLevel2Cache(sm, false);
                                return pc;
                            }
                        }
                    }
                }
            }
        }

        if (checkInheritance)
        {
            sm.checkInheritance(fv); // Find the correct PC class for this object, hence updating the object id
            if (!ignoreCache)
            {
                // Check the cache in case this updated object id is present (since we should use that if available)
                Object oid = sm.getInternalObjectId();
                Object pc = getObjectFromCache(oid);
                if (pc != null)
                {
                    // We have an object with this new object id already so return it with the retrieved field values imposed
                    sm = findStateManager(pc);
                    sm.loadFieldValues(fv); // Load the values retrieved by the query
                    putObjectIntoLevel2Cache(sm, false);
                    return pc;
                }
            }
        }

        // Cache the object as required
        putObjectIntoCache(sm);
        if (txCachedIds != null && !txCachedIds.contains(sm.getInternalObjectId()))
        {
            putObjectIntoLevel2Cache(sm, false);
        }

        return sm.getObject();
    }

    /**
     * Accessor for an object given the object id. 
     * @param id Id of the object.
     * @param fv Field values for the object
     * @param cls the type which the object is (optional). Used to instantiate the object
     * @param ignoreCache true if it must ignore the cache
     * @return The Object
     */
    public synchronized Object findObject(Object id, FieldValues fv, Class cls, boolean ignoreCache)
    {
        assertIsOpen();

        boolean createdHollow = false;
        Object pc = null;
        if (!ignoreCache)
        {
            pc = getObjectFromCache(id);
        }

        if (pc == null)
        {
            // Find direct from the store if supported. NOTE : This ignores the provided FieldValues!
            pc = getStoreManager().getPersistenceHandler().findObject(executionContext, id);
        }

        if (pc == null)
        {
            String className = (cls != null ? cls.getName() : null);
            if (cls == null)
            {
                // Try to derive the class name from the id, since not provided
                className = getStoreManager().getClassNameForObjectID(id, clr, this.getExecutionContext());
                if (className == null)
                {
                    throw new NucleusObjectNotFoundException(LOCALISER.msg("010026"), id);
                }
                if (id instanceof OID)
                {
                    // Try again using the derived class name
                    id = OIDFactory.getInstance(getOMFContext(), className, ((OID)id).getKeyValue());
                    pc = getObjectFromCache(id);
                }
            }

            if (pc == null)
            {
                // Still not found so create a Hollow instance with the supplied field values
                if (cls == null)
                {
                    try
                    {
                        cls = clr.classForName(className, id.getClass().getClassLoader());
                    }
                    catch (ClassNotResolvedException e)
                    {
                        String msg = LOCALISER.msg("010027", getIdentityAsString(id));
                        NucleusLogger.PERSISTENCE.warn(msg);
                        throw new NucleusUserException(msg, e);
                    }
                }

                createdHollow = true;
                StateManager sm = StateManagerFactory.newStateManagerForHollowPopulated(this.getExecutionContext(), cls, id, fv);
                pc = sm.getObject();
                putObjectIntoCache(sm);
                putObjectIntoLevel2Cache(sm, false);
            }
        }

        if (pc != null && fv != null && !createdHollow)
        {
            // Object found in the cache so load the requested fields
            StateManager sm = findStateManager(pc);
            if (sm != null)
            {
                // Load the requested fields
                fv.fetchNonLoadedFields(sm);
            }
        }

        return pc;
    }

    /**
     * Accessor for objects with the specified identities.
     * @param identities Ids of the object(s).
     * @param validate Whether to validate the object state
     * @return The Objects with these ids (same order)
     * @throws NucleusObjectNotFoundException if an object doesn't exist in the datastore
     */
    public synchronized Object[] findObjects(Object[] identities, boolean validate)
    {
        assertIsOpen();

        ApiAdapter api = getApiAdapter();
        Object[] objs = new Object[identities.length];
        Object[] ids = new Object[identities.length];
        List idsToFind = new ArrayList();
        for (int i=0;i<identities.length;i++)
        {
            if (identities[i] == null)
            {
                throw new NucleusUserException(LOCALISER.msg("010044"));
            }

            // Translate the identity if required
            if (getOMFContext().getIdentityTranslator() != null)
            {
                // DataNucleus extension to translate input identities into valid persistent identities.
                IdentityTranslator translator = getOMFContext().getIdentityTranslator();
                ids[i] = translator.getIdentity(this.getExecutionContext(), identities[i]);
            }
            else
            {
                ids[i] = identities[i];
            }

            // Find the object in the cache if possible
            Object pc = getObjectFromCache(ids[i]);
            if (pc != null)
            {
                objs[i] = pc;
                if (ids[i] instanceof SCOID)
                {
                    if (api.isPersistent(pc) && !api.isNew(pc) && !api.isDeleted(pc) && !api.isTransactional(pc))
                    {
                        // JDO2 [5.4.4] Can't return HOLLOW nondurable objects
                        throw new NucleusUserException(LOCALISER.msg("010005"));
                    }
                }
            }
            else
            {
                idsToFind.add(ids[i]);
            }
        }

        // Try to find missing objects direct from the datastore if supported by the StoreManager
        Object[] foundPcs = null;
        foundPcs = getStoreManager().getPersistenceHandler().findObjects(executionContext, idsToFind.toArray());

        int foundPcIdx = 0;

        for (int i=0;i<ids.length;i++)
        {
            Object id = ids[i];
            Object pc = objs[i];
            boolean fromCache = true;
            if (pc == null)
            {
                // Try the "findObjects" results in case supported by StoreManager
                pc = foundPcs[foundPcIdx];
                foundPcIdx++;
            }

            StateManager sm = null;
            if (pc == null)
            {
                // Object not found yet, so work out class name
                String className = null;
                String originalClassName = null;
                boolean checkedClassName = false;
                if (id instanceof SCOID)
                {
                    throw new NucleusUserException(LOCALISER.msg("010006"));
                }
                else if (id instanceof DatastoreUniqueOID)
                {
                    // Should have been found using "persistenceHandler.findObject()"
                    throw new NucleusObjectNotFoundException(LOCALISER.msg("010026"), id);
                }
                else if (api.isDatastoreIdentity(id) || api.isSingleFieldIdentity(id))
                {
                    // OID or SingleFieldIdentity, so check that the implied class is managed
                    originalClassName = getStoreManager().manageClassForIdentity(id, getClassLoaderResolver());
                }
                else
                {
                    // We dont know the object class so try to deduce it from what is known by the StoreManager
                    originalClassName = getStoreManager().getClassNameForObjectID(id, clr, this.getExecutionContext());
                    checkedClassName = true;
                }

                if (validate)
                {
                    // Validate the inheritance level
                    className =
                        (checkedClassName ? originalClassName : getStoreManager().getClassNameForObjectID(id, clr, this.getExecutionContext()));
                    if (className == null)
                    {
                        throw new NucleusObjectNotFoundException(LOCALISER.msg("010026"), id);
                    }

                    if (originalClassName != null && !originalClassName.equals(className))
                    {
                        // Inheritance check implies different inheritance level, so retry
                        if (api.isDatastoreIdentity(id))
                        {
                            // Create new OID using correct target class, and recheck cache
                            id = OIDFactory.getInstance(getOMFContext(), className, ((OID)id).getKeyValue());
                            pc = getObjectFromCache(id);
                        }
                        else if (api.isSingleFieldIdentity(id))
                        {
                            // Create new SingleFieldIdentity using correct targetClass, and recheck cache
                            id = api.getNewSingleFieldIdentity(id.getClass(), getClassLoaderResolver().classForName(className), 
                                api.getTargetKeyForSingleFieldIdentity(id));
                            pc = getObjectFromCache(id);
                        }
                    }
                }
                else
                {
                    className = originalClassName;
                }

                if (pc == null)
                {
                    // Still not found so create a Hollow instance with the supplied field values
                    try
                    {
                        Class pcClass = clr.classForName(className, (id instanceof OID) ? null : id.getClass().getClassLoader());
                        sm = StateManagerFactory.newStateManagerForHollow(this.getExecutionContext(), pcClass, id);
                        pc = sm.getObject();
                        fromCache = false;
                    }
                    catch (ClassNotResolvedException e)
                    {
                        NucleusLogger.PERSISTENCE.warn(LOCALISER.msg("010027", getIdentityAsString(id)));
                        throw new NucleusUserException(LOCALISER.msg("010027", getIdentityAsString(id)), e);
                    }
                }
            }

            // TODO Perform locate of uncached objects in single operation using persistenceHandler.locateObjects
            if (validate)
            {
                if (fromCache && pc != null && api.isTransactional(pc))
                {
                    // JDO2 [12.6.5] Already an object with the same id and it's transactional, so use it
                    objs[i] = pc;
                    continue;
                }

                // User requests validation of the instance so go to the datastore to validate it
                // loading any fetchplan fields that are needed in the process.
                sm = findStateManager(pc);

                if (sm != null && !fromCache)
                {
                    // Cache the object in case we have bidirectional relations that would need to find this
                    putObjectIntoCache(sm);
                }

                try
                {
                    sm.validate();
                }
                catch (NucleusObjectNotFoundException onfe)
                {
                    // Object doesn't exist, so remove from L1 cache
                    removeObjectFromCache(sm.getObject(), sm.getInternalObjectId());
                    throw onfe;
                }

                if (sm.getObject() != pc)
                {
                    // Underlying object was changed in the validation process
                    // Can happen when datastore is responsible for managing object refs e.g db4o
                    // and needs to create the objects itself
                    removeObjectFromCache(sm.getObject(), sm.getInternalObjectId());
                    fromCache = false;
                    pc = sm.getObject();
                }
            }

            objs[i] = pc;

            if (sm != null && !fromCache)
            {
                // Cache the object (update it if already present)
                putObjectIntoCache(sm);
                putObjectIntoLevel2Cache(sm, false);
            }
        }

        return objs;
    }

    /**
     * Accessor for an object given the object id. If validate is false, we return the object
     * if found in the cache, or otherwise a Hollow object with that id. If validate is true
     * we check with the datastore and return an object with the FetchPlan fields loaded.
     * @param id Id of the object.
     * @param validate Whether to validate the object state
     * @param checkInheritance Whether look to the database to determine which class this object is.
     * @param objectClassName Class name for the object with this id (if known, optional)
     * @return The Object with this id
     * @throws NucleusObjectNotFoundException if the object doesn't exist in the datastore
     */
    public synchronized Object findObject(Object id, boolean validate, boolean checkInheritance, String objectClassName)
    {
        assertIsOpen();

        if (id == null)
        {
            throw new NucleusUserException(LOCALISER.msg("010044"));
        }

        if (getOMFContext().getIdentityTranslator() != null)
        {
            // DataNucleus extension to translate input identities into valid persistent identities.
            IdentityTranslator translator = getOMFContext().getIdentityTranslator();
            id = translator.getIdentity(this.getExecutionContext(), id);
        }

        // try to find object in cache(s)
        Object pc = getObjectFromCache(id);
        boolean fromCache = true;
        ApiAdapter api = getApiAdapter();
        if (id instanceof SCOID && pc != null)
        {
            if (api.isPersistent(pc) && !api.isNew(pc) && !api.isDeleted(pc) && !api.isTransactional(pc))
            {
                // JDO2 [5.4.4] Cant return HOLLOW nondurable objects
                throw new NucleusUserException(LOCALISER.msg("010005"));
            }
        }

        if (pc != null && api.isTransactional(pc))
        {
            // JDO2 [12.6.5] If there's already an object with the same id and it's transactional, return it
            return pc;
        }

        StateManager sm = null;
        if (pc == null)
        {
            // Find it direct from the store if the store supports that
            pc = getStoreManager().getPersistenceHandler().findObject(executionContext, id);

            if (pc == null)
            {
                // Object not found in cache(s) with this identity
                String className = null;
                String originalClassName = null;
                boolean checkedClassName = false;
                if (id instanceof SCOID)
                {
                    throw new NucleusUserException(LOCALISER.msg("010006"));
                }
                else if (id instanceof DatastoreUniqueOID)
                {
                    throw new NucleusObjectNotFoundException(LOCALISER.msg("010026"), id);
                }
                else if (api.isDatastoreIdentity(id) || api.isSingleFieldIdentity(id))
                {
                    // DatastoreIdentity or SingleFieldIdentity, so check that the implied class is managed
                    originalClassName = getStoreManager().manageClassForIdentity(id, getClassLoaderResolver());
                }
                else if (objectClassName != null)
                {
                    // Object class name specified so use that directly
                    originalClassName = objectClassName;
                }
                else
                {
                    // We dont know the object class so try to deduce it from what is known by the StoreManager
                    originalClassName = getStoreManager().getClassNameForObjectID(id, clr, this.getExecutionContext());
                    checkedClassName = true;
                }

                if (checkInheritance)
                {
                    // Verify if correct class inheritance level is set
                    if (!checkedClassName)
                    {
                        className = getStoreManager().getClassNameForObjectID(id, clr, this.getExecutionContext());
                    }
                    else
                    {
                        // We just checked the name of the class in the section above so just use that
                        className = originalClassName;
                    }

                    if (className == null)
                    {
                        throw new NucleusObjectNotFoundException(LOCALISER.msg("010026"), id);
                    }

                    if (originalClassName != null && !originalClassName.equals(className))
                    {
                        // Inheritance checking has found a different inherited
                        // object with this identity so create new id
                        if (api.isDatastoreIdentity(id))
                        {
                            // Create new OID using correct target class and recheck the cache
                            id = OIDFactory.getInstance(getOMFContext(), className, ((OID)id).getKeyValue());
                            pc = getObjectFromCache(id);
                        }
                        else if (api.isSingleFieldIdentity(id))
                        {
                            // Create new SingleFieldIdentity using correct targetClass and recheck the cache
                            id = api.getNewSingleFieldIdentity(id.getClass(), getClassLoaderResolver().classForName(className), 
                                    api.getTargetKeyForSingleFieldIdentity(id));
                            pc = getObjectFromCache(id);
                        }
                    }
                }
                else
                {
                    className = originalClassName;
                }

                if (pc == null)
                {
                    // Still not found, so create a Hollow instance with supplied PK values if possible
                    try
                    {
                        Class pcClass = clr.classForName(className, (id instanceof OID) ? null : id.getClass().getClassLoader());
                        if (Modifier.isAbstract(pcClass.getModifiers()))
                        {
                            // This class is abstract so impossible to have an instance of this type
                            throw new NucleusObjectNotFoundException(LOCALISER.msg("010027", 
                                getIdentityAsString(id), className));
                        }

                        sm = StateManagerFactory.newStateManagerForHollow(this.getExecutionContext(), pcClass, id);
                        pc = sm.getObject();
                        fromCache = false;

                        if (!checkInheritance && !validate)
                        {
                            // Mark the StateManager as needing to validate this object before loading fields
                            sm.markForInheritanceValidation();
                        }
                    }
                    catch (ClassNotResolvedException e)
                    {
                        NucleusLogger.PERSISTENCE.warn(LOCALISER.msg("010027", getIdentityAsString(id)));
                        throw new NucleusUserException(LOCALISER.msg("010027", getIdentityAsString(id)), e);
                    }
                }
            }
        }

        if (validate)
        {
            // User requests validation of the instance so go to the datastore to validate it
            // loading any fetchplan fields that are needed in the process.
            if (sm == null)
            {
                sm = findStateManager(pc);
            }

            if (sm != null && !fromCache)
            {
                // Cache the object in case we have bidirectional relations that would need to find this
                putObjectIntoCache(sm);
            }

            try
            {
                sm.validate();
            }
            catch (NucleusObjectNotFoundException onfe)
            {
                // Object doesn't exist, so remove from L1 cache
                removeObjectFromCache(sm.getObject(), sm.getInternalObjectId());
                throw onfe;
            }

            if (sm.getObject() != pc)
            {
                // Underlying object was changed in the validation process. This can happen when the datastore
                // is responsible for managing object references and it no longer recognises the cached value.
                fromCache = false;
                removeObjectFromCache(sm.getObject(), sm.getInternalObjectId());
            }
            if (!fromCache)
            {
                // We created a Hollow PC earlier but then went to the datastore and let it find the real object
                // This allows the datastore to replace this temporary Hollow object with the real datastore object if required
                // This doesnt change with RDBMS datastores since we just pull in fields, but for DB4O we pull in object graphs
                pc = sm.getObject();
            }
        }

        if (sm != null && !fromCache)
        {
            // Cache the object (update it if already present)
            putObjectIntoCache(sm);
            putObjectIntoLevel2Cache(sm, false);
        }

        return pc;
    }

    /**
     * This method returns an object id instance corresponding to the pcClass and key arguments.
     * Operates in 2 modes :-
     * <ul>
     * <li>The class uses SingleFieldIdentity and the key is the value of the key field</li>
     * <li>In all other cases the key is the String form of the object id instance</li>
     * </ul>
     * @param pcClass Class of the PersistenceCapable to create the identity for
     * @param key Value of the key for SingleFieldIdentity (or the toString value)
     * @return The new object-id instance
     */
    public Object newObjectId(Class pcClass, Object key)
    {
        assertIsOpen();
        if (pcClass == null)
        {
            throw new NucleusUserException(LOCALISER.msg("010028"));
        }
        assertClassPersistable(pcClass);

        AbstractClassMetaData cmd = getMetaDataManager().getMetaDataForClass(pcClass, clr);
        if (cmd == null)
        {
            throw new NoPersistenceInformationException(pcClass.getName());
        }

        // If the class is not yet managed, manage it
        if (!getStoreManager().managesClass(cmd.getFullClassName()))
        {
            getStoreManager().addClass(cmd.getFullClassName(), clr);
        }

        Object id = null;
        if (cmd.usesSingleFieldIdentityClass())
        {
            // Single Field Identity
            Class idType = clr.classForName(cmd.getObjectidClass());
            id = getApiAdapter().getNewSingleFieldIdentity(idType, pcClass, key);
        }
        else if (key instanceof java.lang.String)
        {
            // String-based PK (datastore identity or application identity)
            if (cmd.getIdentityType() == IdentityType.APPLICATION)
            {
                if (Modifier.isAbstract(pcClass.getModifiers()) && cmd.getObjectidClass() != null) 
                {
                    try
                    {
                        Constructor c = clr.classForName(cmd.getObjectidClass()).getDeclaredConstructor(new Class[] {java.lang.String.class});
                        id = c.newInstance(new Object[] {(String)key});
                    }
                    catch(Exception e) 
                    {
                        String msg = LOCALISER.msg("010030", cmd.getObjectidClass(), cmd.getFullClassName());
                        NucleusLogger.PERSISTENCE.error(msg);
                        NucleusLogger.PERSISTENCE.error(e);

                        throw new NucleusUserException(msg);
                    }
                }
                else
                {
                    clr.classForName(pcClass.getName(), true);
                    id = getApiAdapter().getNewApplicationIdentityObjectId(pcClass, key);
                }
            }
            else
            {
                id = OIDFactory.getInstance(getOMFContext(), (String)key);
            }
        }
        else
        {
            // Key is not a string, and is not SingleFieldIdentity
            throw new NucleusUserException(LOCALISER.msg("010029", pcClass.getName(), key.getClass().getName()));
        }

        return id;
    }

    /**
     * This method returns an object id instance corresponding to the class name, and the passed
     * object (when using app identity).
     * @param className Name of the class of the object.
     * @param pc The persistable object. Used for application-identity
     * @return A new object ID.
     */
    public Object newObjectId(String className, Object pc)
    {
        AbstractClassMetaData cmd = getMetaDataManager().getMetaDataForClass(className, getClassLoaderResolver()); 
        if (cmd.getIdentityType() == IdentityType.DATASTORE)
        {
            // Populate any strategy value for the "datastore-identity" element
            Object nextIdentifier = getStoreManager().getStrategyValue(this.getExecutionContext(), cmd, -1);
            return OIDFactory.getInstance(getOMFContext(), cmd.getFullClassName(), nextIdentifier);
        }
        else if (cmd.getIdentityType() == IdentityType.APPLICATION)
        {
            return getApiAdapter().getNewApplicationIdentityObjectId(pc, cmd); // All values will have been populated before arriving here
        }
        else
        {
            // All "nondurable" cases (e.g views) will come through here
            return new SCOID(className);
        }
    }

    /**
     * Method to clear an object from the list of dirty objects.
     * @param sm The StateManager
     */
    public synchronized void clearDirty(StateManager sm)
    {
        dirtySMs.remove(sm);
        indirectDirtySMs.remove(sm);
    }

    /**
     * Method to clear all objects marked as dirty (whether directly or indirectly).
     */
    public synchronized void clearDirty()
    {
        dirtySMs.clear();
        indirectDirtySMs.clear();
    }

    /**
     * Method to mark an object (StateManager) as dirty.
     * @param sm The StateManager
     * @param directUpdate Whether the object has had a direct update made on it (if known)
     */
    public synchronized void markDirty(StateManager sm, boolean directUpdate)
    {
        if (tx.isCommitting() && !tx.isActive())
        {
            //post commit cannot change objects (sanity check - avoid changing avoids on detach)
            throw new NucleusException("Cannot change objects when transaction is no longer active.");
        }

        boolean isInDirty = dirtySMs.contains(sm);
        boolean isInIndirectDirty = indirectDirtySMs.contains(sm);
        if (!isDelayDatastoreOperationsEnabled() && !isInDirty && !isInIndirectDirty && 
            dirtySMs.size() >= getOMFContext().getPersistenceConfiguration().getIntProperty("datanucleus.datastoreTransactionFlushLimit"))
        {
            // Reached flush limit so flush
            flushInternal(false);
        }

        if (directUpdate)
        {
            if (isInIndirectDirty)
            {
                indirectDirtySMs.remove(sm);
                dirtySMs.add(sm);
            }
            else if (!isInDirty)
            {
                dirtySMs.add(sm);
                if (txCachedIds != null)
                {
                    txCachedIds.add(sm.getInternalObjectId());
                }
            }
        }
        else
        {
            if (!isInDirty && !isInIndirectDirty)
            {
                // Register as an indirect dirty
                indirectDirtySMs.add(sm);
                if (txCachedIds != null)
                {
                    txCachedIds.add(sm.getInternalObjectId());
                }
            }
        }
    }

    /**
     * Method to mark the specified StateManager as needing an update due to managed relation constraints.
     * @param sm The StateManager
     */
    public void markManagedRelationDirty(StateManager sm)
    {
        if (managedRelationDirtySMs == null)
        {
            managedRelationDirtySMs = new HashSet<StateManager>();
        }
        managedRelationDirtySMs.add(sm);
    }

    /**
     * Returns whether this ObjectManager is currently performing the manage relationships task.
     * @return Whether in the process of managing relations
     */
    public boolean isManagingRelations()
    {
        return managingRelations;
    }

    /**
     * Method to perform managed relationships tasks.
     * @throws NucleusUserException if a consistency check fails
     */
    protected void performManagedRelationships()
    {
        if (getOMFContext().getPersistenceConfiguration().getBooleanProperty("datanucleus.manageRelationships") &&
            managedRelationDirtySMs != null && managedRelationDirtySMs.size() > 0)
        {
            try
            {
                managingRelations = true;

                if (NucleusLogger.PERSISTENCE.isDebugEnabled())
                {
                    NucleusLogger.PERSISTENCE.debug(LOCALISER.msg("013000"));
                }

                if (getOMFContext().getPersistenceConfiguration().getBooleanProperty("datanucleus.manageRelationshipsChecks"))
                {
                    // Tests for negative situations where inconsistently assigned
                    Iterator<StateManager> iter = managedRelationDirtySMs.iterator();
                    while (iter.hasNext())
                    {
                        StateManager sm = iter.next();
                        sm.checkManagedRelations();
                    }
                }

                // Process updates to manage the other side of the relations
                Iterator<StateManager> iter = managedRelationDirtySMs.iterator();
                while (iter.hasNext())
                {
                    StateManager sm = iter.next();
                    sm.processManagedRelations();
                    sm.clearManagedRelations();
                }
                managedRelationDirtySMs.clear();

                if (NucleusLogger.PERSISTENCE.isDebugEnabled())
                {
                    NucleusLogger.PERSISTENCE.debug(LOCALISER.msg("013001"));
                }
            }
            finally
            {
                managingRelations = false;
            }
        }
    }

    /**
     * Returns whether the ObjectManager is in the process of flushing.
     * @return true if the ObjectManager is flushing
     */
    public boolean isFlushing()
    {
        return flushing;
    }

    /**
     * Method callable from external APIs for user-management of flushing.
     * Called by JDO PM.flush, or JPA EM.flush().
     * Performs management of relations, prior to performing internal flush of all dirty/new/deleted
     * instances to the datastore.
     */
    public void flush()
    {
        assertIsOpen();
        if (tx.isActive())
        {
            // Managed Relationships
            performManagedRelationships();

            // Perform internal flush
            flushInternal(true);
        }
    }

    /**
     * This method flushes all dirty, new, and deleted instances to the
     * datastore. It has no effect if a transaction is not active. If a
     * datastore transaction is active, this method synchronizes the cache with
     * the datastore and reports any exceptions. If an optimistic transaction is
     * active, this method obtains a datastore connection and synchronizes the
     * cache with the datastore using this connection. The connection obtained
     * by this method is held until the end of the transaction.
     * @param flushToDatastore Whether to ensure any changes reach the datastore
     *     Otherwise they will be flushed to the datastore manager and leave it to
     *     decide the opportune moment to actually flush them to the datastore
     * @throws NucleusOptimisticException when optimistic locking error(s) occur
     */
    public synchronized void flushInternal(boolean flushToDatastore)
    {
        assertIsOpen();

        if (tx.isActive())
        {
            if (!flushToDatastore && dirtySMs.size() == 0 && indirectDirtySMs.size() == 0)
            {
                // Nothing to flush so abort now
                return;
            }

            if (NucleusLogger.PERSISTENCE.isDebugEnabled())
            {
                NucleusLogger.PERSISTENCE.debug(
                    LOCALISER.msg("010003", (dirtySMs.size() + indirectDirtySMs.size())));
            }
            flushing = true;
            try
            {
                List optimisticFailures = null;

                // Flush all dirty, new, deleted instances to the datastore when transaction is active
                Object[] toFlushDirect;
                synchronized(dirtySMs)
                {
                    toFlushDirect = dirtySMs.toArray();
                    dirtySMs.clear();
                }

                Object[] toFlushIndirect;
                synchronized(indirectDirtySMs)
                {
                    toFlushIndirect = indirectDirtySMs.toArray();
                    indirectDirtySMs.clear();
                }

                // a). direct dirty objects
                for (int i = 0; i < toFlushDirect.length; i++)
                {
                    StateManager sm = (StateManager) toFlushDirect[i];
                    try
                    {
                        sm.flush();
                    }
                    catch (NucleusOptimisticException oe)
                    {
                        if (optimisticFailures == null)
                        {
                            optimisticFailures = new ArrayList();
                        }
                        optimisticFailures.add(oe);
                    }
                }

                // b). indirect dirty objects
                for (int i = 0; i < toFlushIndirect.length; i++)
                {
                    StateManager sm = (StateManager) toFlushIndirect[i];
                    try
                    {
                        sm.flush();
                    }
                    catch (NucleusOptimisticException oe)
                    {
                        if (optimisticFailures == null)
                        {
                            optimisticFailures = new ArrayList();
                        }
                        optimisticFailures.add(oe);
                    }
                }

                // Make sure flushes its changes to the datastore
                if (flushToDatastore)
                {
                    tx.flush();
                }
                if (optimisticFailures != null)
                {
                    // Throw a single NucleusOptimisticException containing all optimistic failures
                    throw new NucleusOptimisticException(LOCALISER.msg("010031"), 
                        (Throwable[])optimisticFailures.toArray(new Throwable[optimisticFailures.size()]));
                }
            }
            finally
            {
                if (NucleusLogger.PERSISTENCE.isDebugEnabled())
                {
                    NucleusLogger.PERSISTENCE.debug(LOCALISER.msg("010004"));
                }
                flushing = false;
            }
        }
    }

    /** Flag for whether running persistence-by-reachability-at-commit */
    private boolean runningPBRAtCommit = false;

    /**
     * Method to perform any post-begin checks.
     */
    public synchronized void postBegin()
    {
        StateManager[] sms = dirtySMs.toArray(new StateManager[dirtySMs.size()]);
        for (int i=0; i<sms.length; i++)
        {
            sms[i].preBegin(tx);
        }
        sms = indirectDirtySMs.toArray(new StateManager[indirectDirtySMs.size()]);
        for (int i=0; i<sms.length; i++)
        {
            sms[i].preBegin(tx);
        }
    }

    /**
     * Method to perform any pre-commit checks.
     */
    public synchronized void preCommit()
    {
        // Make sure all is flushed before we start
        flush();

        if (omf.getBooleanProperty("datanucleus.persistenceByReachabilityAtCommit"))
        {
            // Persistence-by-reachability at commit
            try
            {
                runningPBRAtCommit = true;
                performReachabilityAtCommit();
                getTransaction().flush();
            }
            catch (Throwable t)
            {
                NucleusLogger.PERSISTENCE.error(t);
                if (t instanceof NucleusException)
                {
                    throw (NucleusException) t;
                }
                else
                {
                    throw new NucleusException("Unexpected error during precommit",t);
                }
            }
            finally
            {
                runningPBRAtCommit = false;
            }
        }

        if (omf.hasLevel2Cache())
        {
            // L2 caching of enlisted objects
            performLevel2CacheUpdateAtCommit();
        }

        if (detachAllOnCommit)
        {
            // "detach-on-commit"
            performDetachAllOnTxnEndPreparation();
        }
    }

    /**
     * Accessor for whether the object with this identity is modified in the current transaction.
     * Only returns true when using the L2 cache and the object has been modified during the txn.
     * @param id The identity
     * @return Whether it is modified/new/deleted in this transaction
     */
    public boolean isObjectModifiedInTransaction(Object id)
    {
        if (txCachedIds != null)
        {
            return txCachedIds.contains(id);
        }
        return false;
    }

    /**
     * Method invoked during commit() to perform updates to the L2 cache.
     * <ul>
     * <li>Any objects modified during the current transaction will be added/updated in the L2 cache.</li>
     * <li>Any objects that aren't modified but have been enlisted will be added to the L2 cache.</li>
     * <li>Any objects that are modified but no longer enlisted (due to garbage collection) will be
     * removed from the L2 cache (to avoid giving out old data).</li>
     * </ul>
     */
    private void performLevel2CacheUpdateAtCommit()
    {
        // Lock the L2 cache so nobody else can have it while we are updating objects
        // Without this we can get race conditions between threads taking objects out, and
        // us putting objects in leading to assorted exceptions in AbstractStateManager or
        // in the PC object jdoReplaceField() methods.
        Level2Cache l2Cache = omf.getLevel2Cache();
        synchronized (l2Cache)
        {
            // Process all modified objects adding/updating/removing from L2 cache as appropriate
            Iterator txCachedIter = txCachedIds.iterator();
            while (txCachedIter.hasNext())
            {
                Object id = txCachedIter.next();
                StateManager sm = enlistedSMCache.get(id);
                if (sm == null)
                {
                    // Modified object no longer enlisted so has been GCed, so remove from L2
                    if (NucleusLogger.CACHE.isDebugEnabled())
                    {
                        NucleusLogger.CACHE.debug(LOCALISER.msg("004014",
                            id, String.valueOf(l2Cache.getSize())));
                    }
                    l2Cache.evict(id);
                }
                else
                {
                    // Modified object still enlisted so cacheable
                    if (getApiAdapter().isDeleted(sm.getObject()))
                    {
                        // Object has been deleted so remove from L2 cache
                        if (NucleusLogger.CACHE.isDebugEnabled())
                        {
                            NucleusLogger.CACHE.debug(LOCALISER.msg("004007",
                                StringUtils.toJVMIDString(sm.getObject()),
                                sm.getInternalObjectId(),
                                String.valueOf(l2Cache.getSize())));
                        }
                        l2Cache.evict(getApiAdapter().getIdForObject(sm.getObject()));
                    }
                    else if (!getApiAdapter().isDetached(sm.getObject()))
                    {
                        // Object has been added/modified so update in L2 cache
                        putObjectIntoLevel2CacheInternal(sm, true);
                    }
                }
            }
            txCachedIds.clear();
        }
    }

    /**
     * Method to perform persistence-by-reachability at commit.
     * Utilises txKnownPersistedIds, and txFlushedNewIds, together with txKnownDeletedIds
     * and runs reachability, performing any necessary delettions of no longer reachable objects.
     */
    private void performReachabilityAtCommit()
    {
        if (NucleusLogger.REACHABILITY.isDebugEnabled())
        {
            NucleusLogger.REACHABILITY.debug(LOCALISER.msg("010032"));
        }

        // If we have some new objects in this transaction, and we have some known persisted objects (either
        // from makePersistent in this txn, or enlisted existing objects) then run reachability checks
        if (txKnownPersistedIds.size() > 0 && txFlushedNewIds.size() > 0)
        {
            Set currentReachables = new HashSet();

            // Run "reachability" on all known persistent objects for this txn
            Object ids[] = txKnownPersistedIds.toArray();
            Set objectNotFound = new HashSet();
            for (int i=0; i<ids.length; i++)
            {
                if (!txKnownDeletedIds.contains(ids[i]))
                {
                    if (NucleusLogger.REACHABILITY.isDebugEnabled())
                    {
                        NucleusLogger.REACHABILITY.debug("Performing reachability algorithm on object with id \""+ids[i]+"\"");
                    }
                    try
                    {
                        StateManager sm = findStateManager(findObject(ids[i], true, true, null));
                        sm.runReachability(currentReachables);
                        if (i % 10000 == 0 || i == ids.length-1)
                        {
                            // Flush every 10000 or on the last one to make sure tx cache is empty
                            flushInternal(true);
                        }
                    }
                    catch (NucleusObjectNotFoundException ex)
                    {
                        objectNotFound.add(ids[i]);
                    }
                }
                else
                {
                    // Was deleted earlier so ignore
                }
            }

            // Remove any of the "reachable" instances that are no longer "reachable"
            txFlushedNewIds.removeAll(currentReachables);

            Object nonReachableIds[] = txFlushedNewIds.toArray();
            if (nonReachableIds != null && nonReachableIds.length > 0)
            {
                // For all of instances no longer reachable we need to delete them from the datastore
                // A). Nullify all of their fields.
                // TODO See CORE-3276 for a possible change to this
                for (int i=0; i<nonReachableIds.length; i++)
                {
                    if (NucleusLogger.REACHABILITY.isDebugEnabled())
                    {
                        NucleusLogger.REACHABILITY.debug(LOCALISER.msg("010033", nonReachableIds[i]));
                    }
                    try
                    {
                        if (!objectNotFound.contains(nonReachableIds[i]))
                        {
                            StateManager sm = findStateManager(findObject(nonReachableIds[i], true, true, null));
                            sm.nullifyFields();

                            if (i % 10000 == 0 || i == nonReachableIds.length-1)
                            {
                                // Flush every 10000 or on the last one to clear out dirties
                                flushInternal(true);
                            }
                        }
                    }
                    catch (NucleusObjectNotFoundException ex)
                    {
                        // just ignore if the object does not exist anymore  
                    }
                }

                // B). Remove the objects
                for (int i=0; i<nonReachableIds.length; i++)
                {
                    try
                    {
                        if (!objectNotFound.contains(nonReachableIds[i]))
                        {
                            StateManager sm = findStateManager(findObject(nonReachableIds[i], true, true, null));
                            sm.deletePersistent();
                            if (i % 10000 == 0 || i == nonReachableIds.length-1)
                            {
                                // Flush every 10000 or on the last one to clear out dirties
                                flushInternal(true);
                            }
                        }
                    }
                    catch (NucleusObjectNotFoundException ex)
                    {
                        //just ignore if the file does not exist anymore  
                    }
                }
            }
        }

        if (NucleusLogger.REACHABILITY.isDebugEnabled())
        {
            NucleusLogger.REACHABILITY.debug(LOCALISER.msg("010034"));
        }
    }

    /**
     * Temporary array of StateManagers to detach at commit (to prevent garbage collection). 
     * Set up in preCommit() and used in postCommit().
     */
    private StateManager[] detachAllOnTxnEndSMs = null;

    /**
     * Method to perform all necessary preparation for detach-all-on-commit/detach-all-on-rollback.
     * Identifies all objects affected and makes sure that all fetch plan fields are loaded.
     */
    private void performDetachAllOnTxnEndPreparation()
    {
        // JDO2 spec 12.7.3 "Root instances"
        // "Root instances are parameter instances for retrieve, detachCopy, and refresh; result
        // instances for queries. Root instances for DetachAllOnCommit are defined explicitly by
        // the user via the FetchPlan property DetachmentRoots or DetachmentRootClasses. 
        // If not set explicitly, the detachment roots consist of the union of all root instances of
        // methods executed since the last commit or rollback."
        Collection sms = new ArrayList();
        Collection roots = fetchPlan.getDetachmentRoots();
        Class[] rootClasses = fetchPlan.getDetachmentRootClasses();
        if (roots != null && roots.size() > 0)
        {
            // Detachment roots specified
            Iterator rootsIter = roots.iterator();
            while (rootsIter.hasNext())
            {
                Object obj = rootsIter.next();
                sms.add(findStateManager(obj));
            }
        }
        else if (rootClasses != null && rootClasses.length > 0)
        {
            // Detachment root classes specified
            StateManager[] txSMs = enlistedSMCache.values().toArray(new StateManager[enlistedSMCache.size()]);
            for (int i=0;i<txSMs.length;i++)
            {
                for (int j=0;j<rootClasses.length;j++)
                {
                    // Check if object is of this root type
                    if (txSMs[i].getObject().getClass() == rootClasses[j])
                    {
                        // This SM is for a valid root object
                        sms.add(txSMs[i]);
                        break;
                    }
                }
            }
        }
        else
        {
            // Detach all objects in the L1 cache
            sms.addAll(cache.values());
        }

        // Make sure that all FetchPlan fields are loaded
        Iterator smsIter = sms.iterator();
        while (smsIter.hasNext())
        {
            StateManager sm = (StateManager)smsIter.next();
            Object pc = sm.getObject();
            if (pc != null && !getApiAdapter().isDetached(pc) && !getApiAdapter().isDeleted(pc))
            {
                // Load all fields (and sub-objects) in the FetchPlan
                FetchPlanState state = new FetchPlanState();
                try
                {
                    sm.loadFieldsInFetchPlan(state);
                }
                catch (NucleusObjectNotFoundException onfe)
                {
                    // This object doesnt exist in the datastore at this point.
                    // Either the user has some other process that has deleted it or they have
                    // defined datastore based cascade delete and it has been deleted that way
                    NucleusLogger.PERSISTENCE.warn(LOCALISER.msg("010013",
                        StringUtils.toJVMIDString(pc), sm.getInternalObjectId()));
                    smsIter.remove();
                    // TODO Move the object state to P_DELETED for consistency
                }
            }
        }
        detachAllOnTxnEndSMs = (StateManager[])sms.toArray(new StateManager[sms.size()]);
    }

    /**
     * Method to perform detach-all-on-commit, using the data identified by
     * performDetachAllOnCommitPreparation().
     */
    private void performDetachAllOnTxnEnd()
    {
        try
        {
            runningDetachAllOnTxnEnd = true;

            // Detach all detachment root objects (causes recursion through the fetch plan)
            StateManager[] smsToDetach = detachAllOnTxnEndSMs;
            DetachState state = new DetachState(getApiAdapter());
            for (int i=0;i<smsToDetach.length;i++)
            {
                Object pc = smsToDetach[i].getObject();
                if (pc != null)
                {
                    smsToDetach[i].detach(state);
                }
            }
            detachAllOnTxnEndSMs = null; // No longer need these references
        }
        finally
        {
            runningDetachAllOnTxnEnd = false;
        }
    }

    /**
     * Accessor for whether this ObjectManager is currently running detachAllOnCommit.
     * @return Whether running detachAllOnCommit
     */
    public boolean isRunningDetachAllOnCommit()
    {
        return runningDetachAllOnTxnEnd;
    }

    /**
     * Method to perform detach on close (of the ObjectManager).
     * Processes all (non-deleted) objects in the L1 cache and detaches them.
     */
    private void performDetachOnClose()
    {
        NucleusLogger.PERSISTENCE.debug(LOCALISER.msg("010011"));
        try
        {
            // Start a transaction in case we need to load any unloaded fields
            tx.begin();

            List<StateManager> toDetach = new ArrayList();
            toDetach.addAll(cache.values());
            Iterator<StateManager> iter = toDetach.iterator();
            while (iter.hasNext())
            {
                StateManager sm = iter.next();
                if (sm != null && sm.getObject() != null && 
                    !sm.getObjectManager().getApiAdapter().isDeleted(sm.getObject()))
                {
                    try
                    {
                        sm.detach(new DetachState(getApiAdapter()));
                    }
                    catch (NucleusObjectNotFoundException onfe)
                    {
                        // Catch exceptions for any objects that are deleted in other managers whilst having this open
                    }
                }
            }
            tx.commit();
        }
        finally
        {
            if (tx.isActive())
            {
                tx.rollback();
            }
        }
        NucleusLogger.PERSISTENCE.debug(LOCALISER.msg("010012"));
    }

    /**
     * Commit any changes made to objects managed by the object manager to the database.
     */
    public synchronized void postCommit()
    {
        if (detachAllOnCommit)
        {
            // Detach-all-on-commit
            performDetachAllOnTxnEnd();
        }

        List failures = null;
        try
        {
            // Commit all enlisted StateManagers
            ApiAdapter api = getApiAdapter();
            StateManager[] sms = enlistedSMCache.values().toArray(new StateManager[enlistedSMCache.size()]);
            for (int i = 0; i < sms.length; ++i)
            {
                try
                {
                    // Perform any operations required after committing
                    //TODO this if is due to sms that can have lc == null, why?, should not be here then
                    if (sms[i] != null && 
                        sms[i].getObject() != null &&
                        (api.isPersistent(sms[i].getObject()) || api.isTransactional(sms[i].getObject())))
                    {
                        sms[i].postCommit(getTransaction());
    
                        // TODO Change this check so that we remove all objects that are no longer suitable for caching
                        if (detachAllOnCommit && api.isDetachable(sms[i].getObject()))
                        {
                            // "DetachAllOnCommit" - Remove the object from the L1 cache since it is now detached
                            removeStateManager(sms[i]);
                        }
                    }
                }
                catch (RuntimeException e)
                {
                    if (failures == null)
                    {
                        failures = new ArrayList();
                    }
                    failures.add(e);
                }
            }
        }
        finally
        {
            resetTransactionalVariables();
        }
        if (failures != null && !failures.isEmpty())
        {
            throw new CommitStateTransitionException((Exception[]) failures.toArray(new Exception[failures.size()]));
        }
    }

    /**
     * Rollback any changes made to objects managed by the object manager to the database.
     */
    public synchronized void preRollback()
    {
        ArrayList failures = null;
        try
        {
            Collection sms = enlistedSMCache.values();
            Iterator<StateManager> smsIter = sms.iterator();
            while (smsIter.hasNext())
            {
                StateManager sm = smsIter.next();
                try
                {
                    sm.preRollback(getTransaction());
                }
                catch (RuntimeException e)
                {
                    if (failures == null)
                    {
                        failures = new ArrayList();
                    }
                    failures.add(e);
                }
            }
            clearDirty();
        }
        finally
        {
            resetTransactionalVariables();
        }

        if (failures != null && !failures.isEmpty())
        {
            throw new RollbackStateTransitionException((Exception[]) failures.toArray(new Exception[failures.size()]));
        }

        if (detachAllOnRollback)
        {
            // "detach-on-rollback"
            performDetachAllOnTxnEndPreparation();
        }
    }

    /**
     * Callback invoked after the actual datastore rollback.
     */
    public synchronized void postRollback()
    {
        if (detachAllOnRollback)
        {
            // "detach-on-rollback"
            performDetachAllOnTxnEnd();
        }
    }

    /**
     * Convenience method to reset all state variables for the transaction, performed at commit/rollback.
     */
    private void resetTransactionalVariables()
    {
        enlistedSMCache.clear();
        txEnlistedIds.clear();
        txKnownPersistedIds.clear();
        txKnownDeletedIds.clear();
        txFlushedNewIds.clear();
        dirtySMs.clear();
        indirectDirtySMs.clear();
        fetchPlan.resetDetachmentRoots();
        if (managedRelationDirtySMs != null)
        {
            managedRelationDirtySMs.clear();
        }
        if (txCachedIds != null)
        {
            txCachedIds.clear();
        }
    }

    // -------------------------------------- Cache Management ---------------------------------------

    /**
     * Replace the previous object id for a persistable object with a new one.
     * This is used where we have already added the object to the cache(s) and/or enlisted it in the txn before
     * its real identity was fixed (attributed in the datastore).
     * @param pc The Persistable object
     * @param oldID the old id it was known by
     * @param newID the new id
     */
    public synchronized void replaceObjectId(Object pc, Object oldID, Object newID)
    {
        if (pc == null || getApiAdapter().getIdForObject(pc) == null)
        {
            NucleusLogger.CACHE.warn(LOCALISER.msg("003006"));
            return;
        }

        Object o = cache.get(oldID); //use get() because a cache.remove operation returns a weakReference instance
        if (o != null)
        {
            // Remove the old variant
            if (NucleusLogger.CACHE.isDebugEnabled())
            {
                NucleusLogger.CACHE.debug(LOCALISER.msg("003012", StringUtils.toJVMIDString(pc), 
                    getIdentityAsString(oldID), getIdentityAsString(newID)));
            }
            cache.remove(oldID);
        }

        // Put into both caches
        StateManager sm = findStateManager(pc);
        if (sm != null)
        {
            putObjectIntoCache(sm);
        }

        if (enlistedSMCache.get(oldID) != null)
        {
            // Swap the enlisted object identity
            if (sm != null)
            {
                enlistedSMCache.remove(oldID);
                enlistedSMCache.put(newID, sm);
                if (NucleusLogger.TRANSACTION.isDebugEnabled())
                {
                    NucleusLogger.TRANSACTION.debug(LOCALISER.msg("015018",
                        StringUtils.toJVMIDString(pc), getIdentityAsString(oldID), getIdentityAsString(newID)));
                }
            }
        }

        if (omf.getBooleanProperty("datanucleus.persistenceByReachabilityAtCommit"))
        {
            if (txEnlistedIds.remove(oldID))
            {
                txEnlistedIds.add(newID);
            }
            if (txFlushedNewIds.remove(oldID))
            {
                txFlushedNewIds.add(newID);
            }
            if (txKnownPersistedIds.remove(oldID))
            {
                txKnownPersistedIds.add(newID);
            }
            if (txKnownDeletedIds.remove(oldID))
            {
                txKnownDeletedIds.add(newID);
            }
        }
    }

    /**
     * Convenience method to add an object to the L1 cache.
     * @param sm The State Manager
     */
    public synchronized void putObjectIntoCache(StateManager sm)
    {
        Object id = sm.getInternalObjectId();
        if (id == null || sm.getObject() == null)
        {
            NucleusLogger.CACHE.warn(LOCALISER.msg("003006"));
            return;
        }

        // Put into Level 1 Cache
        Object oldSM = cache.put(sm.getInternalObjectId(), sm);
        if (NucleusLogger.CACHE.isDebugEnabled())
        {
            if (oldSM == null)
            {
                NucleusLogger.CACHE.debug(LOCALISER.msg("003004", 
                    StringUtils.toJVMIDString(sm.getObject()), 
                    getIdentityAsString(sm.getInternalObjectId()),
                    StringUtils.booleanArrayToString(sm.getLoadedFields())));
            }
            else if (oldSM != sm)
            {
                NucleusLogger.CACHE.debug(LOCALISER.msg("003005", 
                    StringUtils.toJVMIDString(sm.getObject()), 
                    getIdentityAsString(sm.getInternalObjectId()),
                    StringUtils.booleanArrayToString(sm.getLoadedFields())));
            }
        }
    }

    /**
     * Method to add/update the managed object into the L2 cache as long as it isn't modified
     * in the current transaction.
     * @param sm StateManager for the object
     * @param updateIfPresent Whether to update it in the L2 cache if already present
     */
    public synchronized void putObjectIntoLevel2Cache(StateManager sm, boolean updateIfPresent)
    {
        if (txCachedIds != null && !txCachedIds.contains(sm.getInternalObjectId()))
        {
            // Object hasn't been modified in this transaction so put in the L2 cache
            putObjectIntoLevel2CacheInternal(sm, updateIfPresent);
        }
    }

    /**
     * Convenience method to add/update an object in the L2 cache.
     * @param sm StateManager of the object to add.
     * @param updateIfPresent Whether to update the L2 cache if it is present
     */
    protected synchronized void putObjectIntoLevel2CacheInternal(StateManager sm, boolean updateIfPresent)
    {
        if (sm.getClassMetaData().isCacheable())
        {
            Object id = sm.getInternalObjectId();
            Level2Cache l2Cache = omf.getLevel2Cache();
            if (!updateIfPresent && l2Cache.containsOid(id))
            {
                // Already present and not wanting to update
                return;
            }

            synchronized (l2Cache)
            {
                CachedPC cachedPC = sm.cache();
                if (cachedPC != null)
                {
                    // Update/add in the L2 cache
                    if (NucleusLogger.CACHE.isDebugEnabled())
                    {
                        if (l2Cache.containsOid(id))
                        {
                            NucleusLogger.CACHE.debug(LOCALISER.msg("004013", 
                                StringUtils.toJVMIDString(sm.getObject()), id, 
                                StringUtils.booleanArrayToString(cachedPC.getLoadedFields()),
                                StringUtils.objectArrayToString(cachedPC.getRelationFieldNames())));
                        }
                        else
                        {
                            NucleusLogger.CACHE.debug(LOCALISER.msg("004003", 
                                StringUtils.toJVMIDString(sm.getObject()), id, 
                                StringUtils.booleanArrayToString(cachedPC.getLoadedFields()),
                                StringUtils.objectArrayToString(cachedPC.getRelationFieldNames())));
                        }
                    }
                    l2Cache.put(id, cachedPC);
                }
            }
        }
    }

    public synchronized void removeObjectFromLevel2Cache(Object id)
    {
        if (id != null)
        {
            Level2Cache l2Cache = omf.getLevel2Cache();
            l2Cache.evict(id);
        }
    }

    /**
     * Convenience method to evict an object from the L1 cache.
     * @param pc The Persistable object
     * @param id The Persistable object id
     */
    public synchronized void removeObjectFromCache(Object pc, Object id)
    {
        if (id != null)
        {
            if (NucleusLogger.CACHE.isDebugEnabled())
            {
                NucleusLogger.CACHE.debug(LOCALISER.msg("003009", 
                    StringUtils.toJVMIDString(pc), getIdentityAsString(id), String.valueOf(cache.size())));
            }
            Object pcRemoved = cache.remove(id);
            if (pcRemoved == null && NucleusLogger.CACHE.isDebugEnabled())
            {
                // For some reason the object isn't in the L1 cache - garbage collected maybe ?
                NucleusLogger.CACHE.debug(LOCALISER.msg("003010",
                    StringUtils.toJVMIDString(pc), getIdentityAsString(id)));
            }
        }
    }

    /**
     * Convenience method to access an object in the cache.
     * Firstly looks in the L1 cache for this ObjectManager, and if not found looks in the L2 cache.
     * @param id Id of the object
     * @return Persistence Capable object (with connected StateManager).
     */
    public synchronized Object getObjectFromCache(Object id)
    {
        Object pc = null;

        // Try Level 1 first
        StateManager sm = (StateManager)cache.get(id);
        if (sm != null)
        {
            pc = sm.getObject();
            if (NucleusLogger.CACHE.isDebugEnabled())
            {
                NucleusLogger.CACHE.debug(LOCALISER.msg("003008", StringUtils.toJVMIDString(pc), 
                    getIdentityAsString(id), 
                    StringUtils.booleanArrayToString(sm.getLoadedFields()),
                    "" + cache.size()));
            }

            // Wipe the detach state that may have been added if the object has been serialised in the meantime
            sm.resetDetachState();

            return pc;
        }
        else
        {
            if (NucleusLogger.CACHE.isDebugEnabled())
            {
                NucleusLogger.CACHE.debug(LOCALISER.msg("003007", getIdentityAsString(id), "" + cache.size()));
            }
        }

        // Try Level 2 since not in Level 1
        if (omf.hasLevel2Cache())
        {
            Level2Cache l2Cache = omf.getLevel2Cache();
            synchronized (l2Cache)
            {
                CachedPC cachedPC = l2Cache.get(id);

                // Create active version of cached object with StateManager connected and same id
                if (cachedPC != null)
                {
                    if (NucleusLogger.CACHE.isDebugEnabled())
                    {
                        NucleusLogger.CACHE.debug(LOCALISER.msg("004015", 
                            getIdentityAsString(id), 
                            StringUtils.booleanArrayToString(cachedPC.getLoadedFields()),
                            StringUtils.objectArrayToString(cachedPC.getRelationFieldNames()),
                            "" + l2Cache.getSize()));
                    }

                    sm = StateManagerFactory.newStateManagerForCachedPC(this.getExecutionContext(), id, cachedPC);
                    pc = sm.getObject(); // Object in P_CLEAN state
                    if (NucleusLogger.CACHE.isDebugEnabled())
                    {
                        NucleusLogger.CACHE.debug(LOCALISER.msg("004006", 
                            getIdentityAsString(id), StringUtils.toJVMIDString(pc)));
                    }
                    if (tx.isActive() && tx.getOptimistic())
                    {
                        // Optimistic txns, so return as P_NONTRANS (as per JDO2 spec)
                        sm.makeNontransactional();
                    }
                    else if (!tx.isActive() && getApiAdapter().isTransactional(pc))
                    {
                        // Non-tx context, so return as P_NONTRANS (as per JDO2 spec)
                        sm.makeNontransactional();
                    }

                    return pc;
                }
                else
                {
                    if (NucleusLogger.CACHE.isDebugEnabled())
                    {
                        NucleusLogger.CACHE.debug(LOCALISER.msg("004005", 
                            getIdentityAsString(id), "" + l2Cache.getSize()));
                    }
                }
            }
        }

        return null;
    }

    /**
     * Convenience method to return the identity as a String.
     * Typically outputs the toString() form of the identity object however with SingleFieldIdentity
     * it outputs the class+key since SingleFieldIdentity just return the key.
     * @param id The id
     * @return String form
     */
    public String getIdentityAsString(Object id)
    {
        if (id == null)
        {
            return null;
        }
        if (getApiAdapter().isSingleFieldIdentity(id))
        {
            return getApiAdapter().getTargetClassNameForSingleFieldIdentity(id) + ":" +
                getApiAdapter().getTargetKeyForSingleFieldIdentity(id);
        }
        else
        {
            return id.toString();
        }
    }

    /**
     * Convenience method to return the setting for serialize read for the current transaction for
     * the specified class name. Returns the setting for the transaction (if set), otherwise falls back to
     * the setting for the class, otherwise returns false.
     * @param className Name of the class
     * @return Setting for serialize read
     */
    public boolean getSerializeReadForClass(String className)
    {
        if (tx.getSerializeRead() != null)
        {
            return tx.getSerializeRead();
        }
        else if (className != null)
        {
            AbstractClassMetaData cmd = getMetaDataManager().getMetaDataForClass(className, clr);
            if (cmd != null)
            {
                return cmd.isSerializeRead();
            }
        }
        return false;
    }

    // ------------------------------------- Queries/Extents --------------------------------------

    /**
     * Extents are collections of datastore objects managed by the datastore,
     * not by explicit user operations on collections. Extent capability is a
     * boolean property of classes that are persistence capable. If an instance
     * of a class that has a managed extent is made persistent via reachability,
     * the instance is put into the extent implicitly.
     * @param pcClass The class to query
     * @param subclasses Whether to include subclasses in the query.
     * @return returns an Extent that contains all of the instances in the
     * parameter class, and if the subclasses flag is true, all of the instances
     * of the parameter class and its subclasses.
     */
    public synchronized Extent getExtent(Class pcClass, boolean subclasses)
    {
        assertIsOpen();
        ClassLoaderResolver clr = getClassLoaderResolver();
        try
        {
            clr.setPrimary(pcClass.getClassLoader());
            assertClassPersistable(pcClass);

            return getStoreManager().getExtent(this.getExecutionContext(), pcClass, subclasses);
        }
        catch (NucleusException jpe)
        {
            // Convert any exceptions into what JDO expects
            throw NucleusJDOHelper.getJDOExceptionForNucleusException(jpe);
        }
        finally
        {
            clr.unsetPrimary();
        }
    }

    /**
     * Construct an empty query instance.
     * @return The query
     */
    public synchronized Query newQuery()
    {
        return getOMFContext().getQueryManager().newQuery("JDOQL", this.getExecutionContext(), null);
    }

    // ------------------------------------- Callback Listeners --------------------------------------

    /**
     * This method removes all previously registered lifecycle listeners.
     * It is necessary to make sure, that a cached ObjectManager (in j2ee environment)
     * will have no listener before the listeners are copied from the OMF.
     * Otherwise they might be registered multiple times.
     */
    public void removeAllInstanceLifecycleListeners()
    {
        if (callbacks != null)
        {
            callbacks.close();
        }
    }

    /**
     * Retrieve the callback handler for this ObjectManager.
     * @return the callback handler
     */
    public CallbackHandler getCallbackHandler()
    {
        if (callbacks != null)
        {
            return callbacks;
        }

        String callbackHandlerClassName = getOMFContext().getPluginManager().getAttributeValueForExtension(
            "org.datanucleus.callbackhandler", "name", getOMFContext().getApi(), "class-name");
        if (callbackHandlerClassName != null)
        {
            try
            {
                callbacks = (CallbackHandler) getOMFContext().getPluginManager().createExecutableExtension(
                    "org.datanucleus.callbackhandler", "name", getOMFContext().getApi(), "class-name",
                    new Class[] {OMFContext.class}, new Object[] {getOMFContext()});
                return callbacks;
            }
            catch (Exception e)
            {
                NucleusLogger.PERSISTENCE.error(LOCALISER.msg("025000", callbackHandlerClassName, e));
            }
        }

        return null;
    }

    /**
     * Method to register a listener for instances of the specified classes.
     * @param listener The listener to sends events to
     * @param classes The classes that it is interested in
     */
    public void addListener(Object listener, Class[] classes)
    {
        assertIsOpen();
        if (listener == null)
        {
            return;
        }
        getCallbackHandler().addListener(listener, classes);
    }

    /**
     * Method to remove a currently registered listener.
     * @param listener The listener to remove.
     */
    public void removeListener(Object listener)
    {
        assertIsOpen();
        if (listener != null)
        {
            getCallbackHandler().removeListener(listener);
        }
    }

    /**
     * Disconnect the registered LifecycleListener
     */
    public void disconnectLifecycleListener()
    {
        // Clear out lifecycle listeners that were registered
        if (callbacks != null)
        {
            callbacks.close();
        }
    }

    // ------------------------------- Assert Utilities ---------------------------------

    /**
     * Method to assert if this Object Manager is open. 
     * Throws a NucleusUserException if the ObjectManager is closed.
     */
    protected void assertIsOpen()
    {
        if (isClosed())
        {
            throw new NucleusUserException(LOCALISER.msg("010002")).setFatal();
        }
    }

    /**
     * Method to assert if the specified class is Persistence Capable.
     * @param cls The class to check
     * @throws ClassNotPersistableException if class is not persistable
     * @throws NoPersistenceInformationException if no metadata/annotations are found for class
     */
    public void assertClassPersistable(Class cls)
    {
        if (cls != null && !getOMFContext().getApiAdapter().isPersistable(cls) && !cls.isInterface())
        {
            throw new ClassNotPersistableException(cls.getName());
        }
        if (!hasPersistenceInformationForClass(cls))
        {
            throw new NoPersistenceInformationException(cls.getName());
        }
    }

    /**
     * Method to assert if the specified object is Detachable. 
     * Throws a ClassNotDetachableException if not capable
     * @param object The object to check
     */
    protected void assertDetachable(Object object)
    {
        if (object != null && !getApiAdapter().isDetachable(object))
        {
            throw new ClassNotDetachableException(object.getClass().getName());
        }
    }

    /**
     * Method to assert if the specified object is detached.
     * Throws a ObjectDetachedException if it is detached.
     * @param object The object to check
     */
    protected void assertNotDetached(Object object)
    {
        if (object != null && getApiAdapter().isDetached(object))
        {
            throw new ObjectDetachedException(object.getClass().getName());
        }
    }

    /**
     * Method to assert if the current transaction is active. Throws a
     * TransactionNotActiveException if not active
     */
    protected void assertActiveTransaction()
    {
        if (!tx.isActive())
        {
            throw new TransactionNotActiveException();
        }
    }
    
    /**
     * Method to assert if the current transaction is active or non transactional
     * writes are allowed.
     * @throws a TransactionNotActiveException if not active and non transactional writes are disabled
     */
    protected void assertWritable()
    {
        if (!getTransaction().isActive() && !getTransaction().getNontransactionalWrite())
        {
            throw new TransactionNotActiveException();
        }
    }
    

    /**
     * Validates that an ImplementationCreator instance is accessible.
     * @throws NucleusUserException if an ImplementationCreator instance does not exist
     */
    protected void assertHasImplementationCreator()
    {
        if (getOMFContext().getImplementationCreator() == null)
        {
            throw new NucleusUserException(LOCALISER.msg("010035"));
        }
    }

    /**
     * Utility method to check if the specified class has reachable metadata or annotations.
     * @param cls The class to check
     * @return Whether the class has reachable metadata or annotations
     */
    public boolean hasPersistenceInformationForClass(Class cls)
    {
        if (cls == null)
        {
            return false;
        }
        
        if ((getMetaDataManager().getMetaDataForClass(cls, getClassLoaderResolver()) != null))
        {
            return true;
        }

        if (cls.isInterface())
        {
            // JDO2 "persistent-interface"
            // Try to create an implementation of the interface at runtime. 
            // It will register the MetaData and make an implementation available
            try
            {
                newInstance(cls);
            }
            catch (RuntimeException ex)
            {
                NucleusLogger.PERSISTENCE.warn(ex);
            }
            return getMetaDataManager().getMetaDataForClass(cls, getClassLoaderResolver()) != null;
        }
        return false;
    }

    // --------------------------- Fetch Groups ---------------------------------

    /** 
     * Convenience accessor for the FetchGroupManager.
     * Creates it if not yet existing.
     * @return The FetchGroupManager
     */
    protected FetchGroupManager getFetchGroupManager()
    {
        if (fetchGrpMgr == null)
        {
            fetchGrpMgr = new FetchGroupManager(getOMFContext());
        }
        return fetchGrpMgr;
    }

    /**
     * Method to add a dynamic FetchGroup for use by this OMF.
     * @param grp The group
     */
    public void addInternalFetchGroup(FetchGroup grp)
    {
        getFetchGroupManager().addFetchGroup(grp);
    }

    /**
     * Method to remove a dynamic FetchGroup from use by this OMF.
     * @param grp The group
     */
    protected void removeInternalFetchGroup(FetchGroup grp)
    {
        getFetchGroupManager().removeFetchGroup(grp);
    }

    /**
     * Accessor for an internal fetch group for the specified class.
     * @param cls The class
     * @param name Name of the group
     * @return The FetchGroup
     * @throws NucleusUserException if the class is not persistable
     */
    public FetchGroup getInternalFetchGroup(Class cls, String name)
    {
        if (!cls.isInterface() && !getOMFContext().getApiAdapter().isPersistable(cls))
        {
            // Class but not persistable!
            throw new NucleusUserException("Cannot create FetchGroup for " + cls + " since it is not persistable");
        }
        else if (cls.isInterface() && !getOMFContext().getMetaDataManager().isPersistentInterface(cls.getName()))
        {
            // Interface but not persistent
            throw new NucleusUserException("Cannot create FetchGroup for " + cls + " since it is not persistable");
        }
        
        return getFetchGroupManager().getFetchGroup(cls, name);
    }

    /**
     * Accessor for the fetch groups for the specified name.
     * @param name Name of the group
     * @return The FetchGroup
     */
    public Set getFetchGroupsWithName(String name)
    {
        return getFetchGroupManager().getFetchGroupsWithName(name);
    }
    
    public ExecutionContext getExecutionContext()
    {
        return executionContext;
    }
}
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