    001    // Copyright 2007, 2009, 2011 The Apache Software Foundation
    002    //
    003    // Licensed under the Apache License, Version 2.0 (the "License");
    004    // you may not use this file except in compliance with the License.
    005    // You may obtain a copy of the License at
    006    //
    007    //     http://www.apache.org/licenses/LICENSE-2.0
    008    //
    009    // Unless required by applicable law or agreed to in writing, software
    010    // distributed under the License is distributed on an "AS IS" BASIS,
    011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    012    // See the License for the specific language governing permissions and
    013    // limitations under the License.
    014
    015    package org.apache.tapestry5.ioc.internal.services;
    016
    017    import org.apache.tapestry5.ioc.*;
    018    import org.apache.tapestry5.ioc.annotations.PreventServiceDecoration;
    019    import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
    020    import org.apache.tapestry5.ioc.services.MasterObjectProvider;
    021    import org.apache.tapestry5.plastic.PlasticUtils;
    022
    023    import java.util.List;
    024
    025    @PreventServiceDecoration
    026    public class MasterObjectProviderImpl implements MasterObjectProvider
    027    {
    028        private final List<ObjectProvider> configuration;
    029
    030        private final OperationTracker tracker;
    031
    032        public MasterObjectProviderImpl(List<ObjectProvider> configuration, OperationTracker tracker)
    033        {
    034            this.configuration = CollectionFactory.newList(configuration);
    035            this.tracker = tracker;
    036
    037            // Add this special case to the front of the list.
    038            this.configuration.add(0, new StaticObjectProvider(OperationTracker.class, tracker));
    039        }
    040
    041        public <T> T provide(final Class<T> objectType, final AnnotationProvider annotationProvider,
    042                             final ObjectLocator locator,
    043                             final boolean required)
    044        {
    045            return tracker.invoke(String.format("Resolving object of type %s using MasterObjectProvider",
    046                    PlasticUtils.toTypeName(objectType)), new Invokable<T>()
    047            {
    048                public T invoke()
    049                {
    050                    for (ObjectProvider provider : configuration)
    051                    {
    052                        T result = provider.provide(objectType, annotationProvider, locator);
    053
    054                        if (result != null) return result;
    055                    }
    056
    057                    // If required, then we must obtain it the hard way, by
    058                    // seeing if there's a single service that implements the interface.
    059
    060                    if (required) return locator.getService(objectType);
    061
    062                    return null;
    063                }
    064            });
    065        }
    066    }