001    // Copyright 2008 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.AnnotationProvider;
018    
019    import java.lang.annotation.Annotation;
020    import java.util.List;
021    
022    /**
023     * Chain of command for {@link org.apache.tapestry5.ioc.AnnotationProvider}.
024     */
025    public class AnnotationProviderChain implements AnnotationProvider
026    {
027        private final AnnotationProvider[] providers;
028    
029        public AnnotationProviderChain(AnnotationProvider[] providers)
030        {
031            this.providers = providers;
032        }
033    
034        /**
035         * Creates an AnnotationProvider from the list of providers.  Returns either an {@link AnnotationProviderChain} or
036         * the sole element in the list.
037         */
038        public static AnnotationProvider create(List<AnnotationProvider> providers)
039        {
040            int size = providers.size();
041    
042            if (size == 1) return providers.get(0);
043    
044            return new AnnotationProviderChain(providers.toArray(new AnnotationProvider[providers.size()]));
045        }
046    
047        public <T extends Annotation> T getAnnotation(Class<T> annotationClass)
048        {
049            for (AnnotationProvider p : providers)
050            {
051                T result = p.getAnnotation(annotationClass);
052    
053                if (result != null) return result;
054            }
055    
056            return null;
057        }
058    }