/*
* Copyright 2013 <a href="mailto:lincolnbaxter@gmail.com">Lincoln Baxter, III</a>
*
* 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.util;
import java.util.Collections;
import java.util.List;
import org.ocpsoft.common.pattern.WeightedComparator;
import org.ocpsoft.common.services.ServiceLoader;
import org.ocpsoft.common.util.Iterators;
import org.ocpsoft.logging.Logger;
import org.ocpsoft.rewrite.spi.InstanceProvider;
/**
* Utility class for looking up instances of Java types. See also {@link InstanceProvider}.
*
* @author <a href="mailto:lincolnbaxter@gmail.com">Lincoln Baxter, III</a>
*/
public final class Instances
{
private static Logger log = Logger.getLogger(Instances.class);
private static List<InstanceProvider> instanceProviders;
private Instances()
{}
/**
* Lookup an instance of the given {@link Class} type.
*/
@SuppressWarnings("unchecked")
public static <T> T lookup(Class<T> type)
{
if (instanceProviders == null) {
instanceProviders = Iterators.asList(ServiceLoader.load(InstanceProvider.class));
Collections.sort(instanceProviders, new WeightedComparator());
ServiceLogger.logLoadedServices(log, InstanceProvider.class, instanceProviders);
}
T result = null;
for (InstanceProvider p : instanceProviders) {
result = (T) p.getInstance(type);
if (result != null)
{
break;
}
}
return result;
}
}