/**
* Licensed to Jasig under one or more contributor license
* agreements. See the NOTICE file distributed with this work
* for additional information regarding copyright ownership.
* Jasig licenses this file to you 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.
*/
package org.jasig.portal.portlet.registry;
import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import org.jasig.portal.portlet.om.IPortletEntityDescriptor;
import org.jasig.portal.portlet.om.IPortletEntityId;
import org.jasig.portal.utils.threading.NoopLock;
import com.google.common.base.Function;
/**
* Utility for caching portlet entities and entity data in memory. Ensures a consistent view for accessing the data by
* different sets of keys
*
* @author Eric Dalquist
* @version $Revision$
* @param <T>
*/
class PortletEntityCache<T extends IPortletEntityDescriptor> implements Serializable {
private static final long serialVersionUID = 1L;
private final Lock writeLock;
private final Lock readLock;
private final Map<SubscribeKey, T> entitiesBySubscribeKey = new HashMap<SubscribeKey, T>();
private final Map<IPortletEntityId, T> entitiesById = new HashMap<IPortletEntityId, T>();
public PortletEntityCache() {
this(true);
}
/**
* @param threadSafe If set to false no locking is done around read or write operations and this class is NOT thread safe
*/
public PortletEntityCache(boolean threadSafe) {
if (threadSafe) {
final ReadWriteLock cacheLock = new ReentrantReadWriteLock(true);
writeLock = cacheLock.writeLock();
readLock = cacheLock.readLock();
}
else {
writeLock = NoopLock.INSTANCE;
readLock = NoopLock.INSTANCE;
}
}
public T storeIfAbsentEntity(IPortletEntityId portletEntityId, Function<IPortletEntityId, T> entityCreator) {
//Check if the entity already exists (uses a read lock)
T existingEntity = this.getEntity(portletEntityId);
if (existingEntity != null) {
return existingEntity;
}
writeLock.lock();
try {
//Check again inside the write lock
existingEntity = this.entitiesById.get(portletEntityId);
if (existingEntity != null) {
return existingEntity;
}
final T entity = entityCreator.apply(portletEntityId);
this.storeEntity(entity);
return entity;
}
finally {
writeLock.unlock();
}
}
public T storeIfAbsentEntity(T entity) {
final IPortletEntityId portletEntityId = entity.getPortletEntityId();
//Check if the entity already exists (uses a read lock)
T existingEntity = this.getEntity(portletEntityId);
if (existingEntity != null) {
return existingEntity;
}
writeLock.lock();
try {
//Check again inside the write lock
existingEntity = this.entitiesById.get(portletEntityId);
if (existingEntity != null) {
return existingEntity;
}
this.storeEntity(entity);
}
finally {
writeLock.unlock();
}
return entity;
}
public void storeEntity(T entity) {
writeLock.lock();
try {
final SubscribeKey subscribeKey = new SubscribeKey(entity.getUserId(), entity.getLayoutNodeId());
this.entitiesBySubscribeKey.put(subscribeKey, entity);
this.entitiesById.put(entity.getPortletEntityId(), entity);
}
finally {
writeLock.unlock();
}
}
public T getEntity(String layoutNodeId, int userId) {
if (this.entitiesBySubscribeKey.isEmpty()) {
return null;
}
readLock.lock();
try {
final SubscribeKey subscribeKey = new SubscribeKey(userId, layoutNodeId);
return this.entitiesBySubscribeKey.get(subscribeKey);
}
finally {
readLock.unlock();
}
}
public T getEntity(IPortletEntityId portletEntityId) {
if (this.entitiesById.isEmpty()) {
return null;
}
readLock.lock();
try {
return this.entitiesById.get(portletEntityId);
}
finally {
readLock.unlock();
}
}
public void removeEntity(IPortletEntityId portletEntityId) {
writeLock.lock();
try {
final T entity = this.entitiesById.remove(portletEntityId);
if (entity != null) {
final int userId = entity.getUserId();
final String layoutNodeId = entity.getLayoutNodeId();
final SubscribeKey subscribeKey = new SubscribeKey(userId, layoutNodeId);
this.entitiesBySubscribeKey.remove(subscribeKey);
}
}
finally {
writeLock.unlock();
}
}
}