/*
* JBoss, Home of Professional Open Source
* Copyright 2011, Red Hat, Inc. and/or its affiliates, and individual
* contributors by the @authors tag. See the copyright.txt in the
* distribution for a full listing of individual contributors.
*
* 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.
*/
package org.ocpsoft.rewrite.cdi.manager;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.ServiceLoader;
import javax.enterprise.inject.spi.BeanManager;
import javax.enterprise.inject.spi.Extension;
import javax.inject.Inject;
import org.ocpsoft.common.pattern.WeightedComparator;
import org.ocpsoft.rewrite.cdi.spi.BeanManagerProvider;
/**
* <p>
* A utility for use in non-managed classes, which are not able to obtain a reference to the {@link BeanManager} using
* injection.
* </p>
* <p/>
* <p>
* {@link BeanManagerProvider} is an SPI that may be implemented to allow third parties to register custom methods of
* looking up the BeanManager in an external context. This class will consult implementations according to precedence.
* </p>
* <p/>
* <p>
* <b>**WARNING**</b> This class is <b>NOT</b> a clever way to get the BeanManager, and should be <b>avoided at all
* costs</b>. If you need a handle to the {@link BeanManager} you should probably register an {@link Extension} instead
* of using this class; have you tried using @{@link Inject}?
* </p>
* <p/>
* <p>
* If you think you need to use this class, chat to the community and make sure you aren't missing a trick!
* </p>
*
* @author Pete Muir
* @author Nicklas Karlsson
* @author <a href="http://community.jboss.org/people/dan.j.allen">Dan Allen</a>
* @author Stuart Douglas
* @see BeanManagerProvider
* @see BeanManagerAware
*/
public class BeanManagerLocator
{
private volatile BeanManager beanManager;
private volatile boolean lookupPerformed = false;
private volatile BeanManagerProvider locatingProvider;
private volatile List<BeanManagerProvider> providers;
/**
* If a lookup has not yet been performed, consult registered {@link BeanManagerProvider} implementations to locate
* the {@link BeanManager} and return the result. If the {@link BeanManager} cannot be resolved, throw a
* {@link BeanManagerUnavailableException}.
*
* @return the BeanManager for the current bean archive
* @throws BeanManagerUnavailableException if the BeanManager cannot be resolved
*/
public BeanManager getBeanManager()
{
if (!lookupPerformed) {
lookupBeanManager();
}
if (beanManager == null) {
throw new BeanManagerUnavailableException(providers);
}
return beanManager;
}
/**
* If a lookup has not yet been performed, consult registered {@link BeanManagerProvider} implementations to locate
* the {@link BeanManager} and return whether it was found, caching the result.
*
* @return <code>true</code> if the bean manager has been found, otherwise <code>false</code>
*/
public boolean isBeanManagerAvailable()
{
if (!lookupPerformed) {
lookupBeanManager();
}
return beanManager != null;
}
/**
* Return the {@link BeanManagerProvider} that was used to locate the BeanManager. This method will not attempt a
* lookup.
*
* @return the BeanManagerProvider implementation
*/
public BeanManagerProvider getLocatingProvider()
{
return locatingProvider;
}
private synchronized void lookupBeanManager()
{
if (!lookupPerformed) {
final List<BeanManagerProvider> providers = loadServices();
Collections.sort(providers, new WeightedComparator());
for (BeanManagerProvider provider : providers) {
beanManager = provider.getBeanManager();
if (beanManager != null) {
locatingProvider = provider;
break;
}
}
this.providers = providers;
lookupPerformed = true;
}
}
private List<BeanManagerProvider> loadServices()
{
List<BeanManagerProvider> providers = new ArrayList<BeanManagerProvider>();
for (Iterator<BeanManagerProvider> it = ServiceLoader.load(BeanManagerProvider.class).iterator(); it.hasNext();) {
providers.add(it.next());
}
return providers;
}
}