/*
* Copyright (c) 2008, Rickard Öberg. All Rights Reserved.
*
* 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.qi4j.api.service.importer;
import java.util.ArrayList;
import java.util.List;
import org.qi4j.api.injection.scope.Structure;
import org.qi4j.api.service.Availability;
import org.qi4j.api.service.ImportedServiceDescriptor;
import org.qi4j.api.service.ServiceFinder;
import org.qi4j.api.service.ServiceImporter;
import org.qi4j.api.service.ServiceImporterException;
import org.qi4j.api.service.ServiceReference;
import org.qi4j.api.service.qualifier.ServiceQualifier;
import org.qi4j.functional.Iterables;
import org.qi4j.functional.Specification;
/**
* If several services are available with a given type, and you want to constrain
* the current module to use a specific one, then use this importer. Specify a
* Specification<ServiceReference<T>> criteria as meta-info for the service, which will be applied
* to the list of available services, and the first match will be chosen.
*
* This importer will avoid selecting itself, as could be possible if the ServiceQualifier.first()
* filter is used.
*/
public final class ServiceSelectorImporter<T>
implements ServiceImporter<T>
{
@Structure
private ServiceFinder locator;
@Override
@SuppressWarnings( { "raw", "unchecked" } )
public T importService( ImportedServiceDescriptor serviceDescriptor )
throws ServiceImporterException
{
Specification<ServiceReference<?>> selector = serviceDescriptor.metaInfo( Specification.class );
Class serviceType = Iterables.first( serviceDescriptor.types() );
Iterable<ServiceReference<T>> services = locator.findServices( serviceType );
List<ServiceReference<T>> filteredServices = new ArrayList<>();
for( ServiceReference<T> service : services )
{
Specification selector1 = service.metaInfo( Specification.class );
if( selector1 != null && selector1 == selector )
{
continue;
}
filteredServices.add( service );
}
T service = ServiceQualifier.firstService( selector, filteredServices );
if( service == null )
{
throw new ServiceImporterException( "Could not find any service to import that matches the given specification for " + serviceDescriptor
.identity() );
}
return service;
}
@Override
public boolean isAvailable( T instance )
{
return !( instance instanceof Availability ) || ( (Availability) instance ).isAvailable();
}
}