content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * 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.ambari.server.events.publishers;
  
  import org.apache.ambari.server.events.ClusterEvent;
  
  import com.google.common.eventbus.EventBus;
  import com.google.inject.Singleton;
  
  /**
   * The {@link VersionEventPublisher} is used to publish instances of
   * {@link ClusterEvent} to any {@link com.google.common.eventbus.Subscribe} interested.
   * It uses a single-threaded, serial {@link EventBus}.
   */
  @Singleton
  public class VersionEventPublisher {
    /**
     * A single threaded event bus for processing version events serially.
     */
    private final EventBus m_eventBus;
  
    /**
     * Constructor.
     */
    public VersionEventPublisher() {
      m_eventBus = new EventBus("version-event-bus");
    }
  
    /**
     * Publishes the specified event to all registered listeners that
     * {@link com.google.common.eventbus.Subscribe} to any of the
     * {@link ClusterEvent} instances.
     *
     * @param event the event
     */
    public void publish(ClusterEvent event) {
      m_eventBus.post(event);
    }
  
    /**
     * Register a listener to receive events. The listener should use the
     * {@link com.google.common.eventbus.Subscribe} annotation.
     *
     * @param object
     *          the listener to receive events.
     */
    public void register(Object object) {
      m_eventBus.register(object);
    }
  }
  