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 * Licensed to the Apache Software Foundation (ASF) under one
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 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you 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.apache.olingo.odata2.annotation.processor.api;

import java.util.Collection;

import org.apache.olingo.odata2.api.ODataService;
import org.apache.olingo.odata2.api.exception.ODataException;

/**
 * AnnotationServiceFactory which provides an AnnotationService which handles java beans (classes)
 * annotated with annotation from <code>org.apache.olingo.olingo-odata2-api-annotation</code> module
 * (see package <code>org.apache.olingo.odata2.api.annotation.edm</code>).
 */
public abstract class AnnotationServiceFactory {

  private static final String IMPLEMENTATION =
      "org.apache.olingo.odata2.annotation.processor.core.rt.AnnotationServiceFactoryImpl";

  /**
   * Create a runtime delegate instance from the core library. The core
   * library (org.apache.olingo.odata2.annotation.processor.core) needs to be included into the classpath
   * of the using application.
   * @return implementation instance
   */
  private static AnnotationServiceFactoryInstance getInstance() {
    AnnotationServiceFactoryInstance delegate;

    try {
      final Class<?> clazz = Class.forName(IMPLEMENTATION);
      /*
       * We explicitly do not use the singleton pattern to keep the server state free
       * and avoid class loading issues also during hot deployment.
       */
      final Object object = clazz.newInstance();
      delegate = (AnnotationServiceFactoryInstance) object;

    } catch (final Exception e) {
      throw new RuntimeException(e);
    }
    return delegate;
  }

  /**
   * Interface to be implemented for an instance of a {@link AnnotationServiceFactoryInstance} which
   * provides an {@link ODataService} based on annotation from
   * <code>org.apache.olingo.olingo-odata2-api-annotation</code> module
   * (see package <code>org.apache.olingo.odata2.api.annotation.edm</code>).
   */
  public interface AnnotationServiceFactoryInstance {
    /**
     * Create an {@link ODataService} which is based on an EDM and Processor which are using the annotations from
     * <code>org.apache.olingo.olingo-odata2-api-annotation</code> module
     * (see package <code>org.apache.olingo.odata2.api.annotation.edm</code>) to define the model and access the data.
     * 
     * @param modelPackage package name which is scanned for annotated classes
     * @return service an {@link ODataService} based on on an EDM and Processor which are using annotations
     * for model definition and data access.
     * @throws ODataException if an error during initialization occurs
     */
    public ODataService createAnnotationService(String modelPackage) throws ODataException;

    /**
     * Create an {@link ODataService} which is based on an EDM and Processor which are using the annotations from
     * <code>org.apache.olingo.olingo-odata2-api-annotation</code> module
     * (see package <code>org.apache.olingo.odata2.api.annotation.edm</code>) to define the model and access the data.
     * 
     * @param modelPackage classes (which are annotated) which will be used for EDM definition and data access.
     * @return service an {@link ODataService} based on on an EDM and Processor which are using annotations
     * for model definition and data access.
     * @throws ODataException if an error during initialization occurs
     */
    public ODataService createAnnotationService(Collection<Class<?>> annotatedClasses) throws ODataException;
  }

  /**
   * Create an {@link ODataService} which is based on an EDM and Processor which are using the annotations from
   * <code>org.apache.olingo.olingo-odata2-api-annotation</code> module
   * (see package <code>org.apache.olingo.odata2.api.annotation.edm</code>) to define the model and access the data.
   * 
   * @param modelPackage package name which is scanned for annotated classes
   * @return service an {@link ODataService} based on on an EDM and Processor which are using annotations
   * for model definition and data access.
   * @throws ODataException if an error during initialization occurs
   */
  public static ODataService createAnnotationService(final String modelPackage) throws ODataException {
    return getInstance().createAnnotationService(modelPackage);
  }

  /**
   * Create an {@link ODataService} which is based on an EDM and Processor which are using the annotations from
   * <code>org.apache.olingo.olingo-odata2-api-annotation</code> module
   * (see package <code>org.apache.olingo.odata2.api.annotation.edm</code>) to define the model and access the data.
   * 
   * @param modelPackage classes (which are annotated) which will be used for EDM definition and data access.
   * @return service an {@link ODataService} based on on an EDM and Processor which are using annotations
   * for model definition and data access.
   * @throws ODataException if an error during initialization occurs
   */
  public static ODataService createAnnotationService(final Collection<Class<?>> annotatedClasses)
      throws ODataException {
    return getInstance().createAnnotationService(annotatedClasses);
  }
}