OsgiAbstractJobProducerEndpoint.java

/**
 * Licensed to The Apereo Foundation under one or more contributor license
 * agreements. See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 *
 * The Apereo Foundation licenses this file to you under the Educational
 * Community 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://opensource.org/licenses/ecl2.txt
 *
 * 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.opencastproject.rest;

import static java.lang.String.format;

import org.opencastproject.job.api.JobProducer;
import org.opencastproject.serviceregistry.api.ServiceRegistry;

/**
 * Refined implementation of {@link org.opencastproject.rest.AbstractJobProducerEndpoint} suitable for use in an
 * OSGi environment.
 * <p>
 * OSGi dependency injection methods are provided to reduce the amount of boilerplate code needed per
 * service implementation.
 * <p>
 * Declare as type variable the {@linkplain AbstractJobProducerEndpoint#getService() job producing service} on which the
 * endpoint depends.
 * <p>
 * <strong>Example:</strong> The endpoint for the WorkflowService can be declared like this:
 * <pre>
 *   public final class WorkflowServiceEndpoint extends OsgiAbstractJobProducerEndpoint<WorkflowServiceImpl>
 * </pre>
 * <p>
 * <strong>Implementation note:</strong> Type variable <code>A</code> <em>cannot</em> have upper bound
 * {@link org.opencastproject.job.api.JobProducer}. Even though this may seem reasonable it will cause trouble
 * with OSGi dependency injection. The dependency will most likely be declared on the service's <em>interface</em>
 * and <em>not</em> the concrete implementation. But only the concrete implementation is a <code>JobProducer</code>.
 * With <code>A</code> having an upper bound of <code>JobProducer</code> the signature of {@link #setService(Object)}
 * will be fixed to that bound: <code>setService(JobProducer)</code>. Now the service cannot be injected anymore.
 */
public abstract class OsgiAbstractJobProducerEndpoint<A> extends AbstractJobProducerEndpoint {
  private A service;
  private ServiceRegistry serviceRegistry;

  @Override
  public JobProducer getService() {
    if (service instanceof JobProducer) {
      return (JobProducer) service;
    } else {
      throw new RuntimeException(format("Service %s is expected to be of type JobProducer", service));
    }
  }

  public void setService(A service) {
    this.service = service;
  }

  public A getSvc() {
    return service;
  }

  @Override
  public ServiceRegistry getServiceRegistry() {
    return serviceRegistry;
  }

  public void setServiceRegistry(ServiceRegistry serviceRegistry) {
    this.serviceRegistry = serviceRegistry;
  }
}