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
015package org.apache.tapestry5.commons.internal.services;
016
017import org.apache.tapestry5.commons.AnnotationProvider;
018
019import java.lang.annotation.Annotation;
020import java.util.List;
021
022/**
023 * Chain of command for {@link org.apache.tapestry5.commons.AnnotationProvider}.
024 */
025public 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    @Override
048    public <T extends Annotation> T getAnnotation(Class<T> annotationClass)
049    {
050        for (AnnotationProvider p : providers)
051        {
052            T result = p.getAnnotation(annotationClass);
053
054            if (result != null) return result;
055        }
056
057        return null;
058    }
059}