    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}