ViewScannerService.java

/*****************************************************************************
 * Copyright 2011 Zdenko Vrabel
 *
 * 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.zdevra.guice.mvc;

import java.lang.annotation.Annotation;
import java.util.Collection;
import java.util.Collections;
import java.util.Set;

import com.google.inject.Inject;
import com.google.inject.Singleton;

/**
 * This service provide scanning of controller class or controller's method,
 * where is looking for view annotations, then constructs and returns a 
 * view instance for concrete controller's class or method.
 *
 * This service contains various scanners for various views. If you want
 * create your own view annotation, you will create own scanner as a 
 * implementation of {@link ViewScanner} interface and then you will
 * register it in {@link MvcModule}.
 * 
 * <p>How to register custom scanner into service
 * <pre class="prettyprint">
 * class CustomModule extends MvcModule {
 *    protected void configureControllers() {
 *       ...
 *       registerViewScanner(Custom1ViewScanner.class);
 *       registerViewScanner(new Custom2ViewScanner());
 *       ...
 *    }
 * }
 * </pre>
 * 
 */
@Singleton
class ViewScannerService {

    private Collection<ViewScanner> scanners;

    @Inject
    public ViewScannerService(Set<ViewScanner> scanners) {
        this.scanners = Collections.unmodifiableCollection(scanners);
    }

    public ViewPoint scan(Annotation[] controllerAnnotations) {
        for (ViewScanner scanner : scanners) {
            ViewPoint view = scanner.scan(controllerAnnotations);
            if (view != null && view != ViewPoint.NULL_VIEW) {
                return view;
            }
        }
        return ViewPoint.NULL_VIEW;
    }
}