/*
* JBoss, Home of Professional Open Source.
* Copyright 2011, Red Hat, Inc., and individual contributors
* as indicated by the @author tags. See the copyright.txt file in the
* distribution for a full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.jboss.as.ejb3.component.entity.entitycache;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicInteger;
import javax.ejb.NoSuchEntityException;
import org.jboss.as.ejb3.logging.EjbLogger;
import org.jboss.as.ejb3.component.entity.EntityBeanComponent;
import org.jboss.as.ejb3.component.entity.EntityBeanComponentInstance;
/**
* @author John Bailey
* @author <a href="wfink@redhat.com">Wolf-Dieter Fink</a>
*/
public class ReferenceCountingEntityCache implements ReadyEntityCache {
private final ConcurrentMap<Object, CacheEntry> cache = new ConcurrentHashMap<Object, CacheEntry>();
private final EntityBeanComponent component;
public ReferenceCountingEntityCache(final EntityBeanComponent component) {
this.component = component;
}
public synchronized void create(final EntityBeanComponentInstance instance) {
final CacheEntry entry = realCreate(instance);
entry.referenceCount.incrementAndGet();
}
private CacheEntry realCreate(final EntityBeanComponentInstance instance) {
final CacheEntry cacheEntry = new CacheEntry(instance);
final CacheEntry existing = cache.putIfAbsent(instance.getPrimaryKey(), cacheEntry);
if (existing != null) {
if (existing.instance.isRemoved()) {
//this happens in an instance is removed and then re-added in the space of the same transaction
existing.replacedInstance = instance;
} else {
throw EjbLogger.ROOT_LOGGER.instanceAlreadyRegisteredForPK(instance.getPrimaryKey());
}
}
return cacheEntry;
}
@Override
public synchronized boolean contains(final Object key) {
if(cache.containsKey(key)) {
final CacheEntry cacheEntry = cache.get(key);
return true;
}
return false;
}
@Override
public synchronized boolean containsNotRemoved(final Object key) {
if(cache.containsKey(key)) {
final CacheEntry cacheEntry = cache.get(key);
if (cacheEntry.replacedInstance != null) {
return !cacheEntry.replacedInstance.isRemoved();
} else {
return !cacheEntry.instance.isRemoved();
}
}
return false;
}
public synchronized EntityBeanComponentInstance get(final Object key) throws NoSuchEntityException {
if (!cache.containsKey(key)) {
final EntityBeanComponentInstance instance = createInstance(key);
realCreate(instance);
}
final CacheEntry cacheEntry = cache.get(key);
cacheEntry.referenceCount.incrementAndGet();
if (cacheEntry.replacedInstance != null) {
return cacheEntry.replacedInstance;
} else {
return cacheEntry.instance;
}
}
public synchronized void release(final EntityBeanComponentInstance instance, boolean success) {
if (instance.isDiscarded()) {
return;
}
if (instance.getPrimaryKey() == null) return; // TODO: Should this be an Exception
final CacheEntry cacheEntry = cache.get(instance.getPrimaryKey());
if (cacheEntry == null) {
throw EjbLogger.ROOT_LOGGER.entityBeanInstanceNotFoundInCache(instance);
}
if (cacheEntry.replacedInstance != null) {
//this can happen if an entity is removed and a new entity with the same PK is added in a transactions
if (instance == cacheEntry.replacedInstance) {
if (success) {
cacheEntry.instance = cacheEntry.replacedInstance;
} else if (cacheEntry.instance.isDiscarded()) {
//if the TX was a failure, and the previous instance has been discarded
//we just remove the entry and return
cache.remove(instance.getPrimaryKey());
return;
}
cacheEntry.replacedInstance = null;
}
}
//TODO: this should probably be somewhere else
//roll back unsuccessful removal
if (!success && instance.isRemoved()) {
instance.setRemoved(false);
}
if (cacheEntry.referenceCount.decrementAndGet() == 0) {
final Object pk = instance.getPrimaryKey();
try {
instance.passivate();
component.releaseEntityBeanInstance(instance);
} finally {
cache.remove(pk);
}
}
}
public synchronized void discard(final EntityBeanComponentInstance instance) {
if(instance.getPrimaryKey() == null) {
//instance has already been passivated
return;
}
final CacheEntry entry = cache.get(instance.getPrimaryKey());
if (entry != null) {
if (instance == entry.replacedInstance) {
//this instance that is being discarded is the new instance
//we can just set it to null
entry.replacedInstance = null;
} else if (entry.replacedInstance == null) {
//if there is a new instance we cannot discard the entry entirely
cache.remove(instance.getPrimaryKey());
}
}
}
public void start() {
}
public void stop() {
}
private EntityBeanComponentInstance createInstance(final Object pk) {
final EntityBeanComponentInstance instance = component.acquireUnAssociatedInstance();
instance.activate(pk);
return instance;
}
private class CacheEntry {
private final AtomicInteger referenceCount = new AtomicInteger(0);
private volatile EntityBeanComponentInstance instance;
private volatile EntityBeanComponentInstance replacedInstance;
private CacheEntry(EntityBeanComponentInstance instance) {
this.instance = instance;
}
}
}