plugins/org.eclipse.emf.cdo.server.hibernate/src/org/eclipse/emf/cdo/server/internal/hibernate/tuplizer/PersistableListHolder.java

/***************************************************************************
 * Copyright (c) 2004 - 2008 Martin Taal and others
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *    Martin Taal - copied from CDORevisionPropertyHandler and adapted
 **************************************************************************/
package org.eclipse.emf.cdo.server.internal.hibernate.tuplizer;

import org.eclipse.emf.cdo.common.model.CDOFeature;
import org.eclipse.emf.cdo.common.revision.CDORevision;
import org.eclipse.emf.cdo.server.internal.hibernate.bundle.OM;

import org.eclipse.net4j.util.om.trace.ContextTracer;

import org.hibernate.collection.PersistentCollection;

import java.util.HashMap;
import java.util.Map;

/**
 * Keeps mappings from object/feature combinations to a hibernate persistable list. This works because the write action
 * is done in one thread.
 * 
 * @author Martin Taal
 */
public class PersistableListHolder
{
  private static final ContextTracer TRACER = new ContextTracer(OM.DEBUG, PersistableListHolder.class);

  private static PersistableListHolder instance = new PersistableListHolder();

  private ThreadLocal<Map<Key, PersistentCollection>> listMapping = new ThreadLocal<Map<Key, PersistentCollection>>();

  public PersistableListHolder()
  {
  }

  public void putListMapping(Object target, CDOFeature cdoFeature, PersistentCollection collection)
  {
    Key key = new Key(target, cdoFeature);
    getListMapping().put(key, collection);
    if (TRACER.isEnabled())
    {
      TRACER.trace("Stored hb list in threadlocal: " + ((CDORevision)target).getCDOClass().getName() + "."
          + cdoFeature.getName());
    }
  }

  public PersistentCollection getListMapping(Object target, CDOFeature cdoFeature)
  {
    Key key = new Key(target, cdoFeature);
    return getListMapping().get(key);
  }

  private Map<Key, PersistentCollection> getListMapping()
  {
    if (listMapping.get() == null)
    {
      listMapping.set(new HashMap<Key, PersistentCollection>());
    }

    return listMapping.get();
  }

  public static PersistableListHolder getInstance()
  {
    return instance;
  }

  public static void setInstance(PersistableListHolder instance)
  {
    PersistableListHolder.instance = instance;
  }

  private static final class Key
  {
    private Object owner;

    private CDOFeature cdoFeature;

    public Key(Object owner, CDOFeature cdoFeature)
    {
      this.owner = owner;
      this.cdoFeature = cdoFeature;
    }

    @Override
    public boolean equals(Object obj)
    {
      if (!(obj instanceof Key))
      {
        return false;
      }

      Key otherKey = (Key)obj;
      // the owner is uniquely present in mem, the same applies for the cdoFeature
      // therefore == is allowed
      return owner == otherKey.owner && cdoFeature == otherKey.cdoFeature;
    }

    @Override
    public int hashCode()
    {
      return owner.hashCode() + cdoFeature.hashCode();
    }
  }
}