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.notifications;
  
  import java.util.HashMap;
  import java.util.Map;
  
  import com.google.inject.Singleton;
  
  /**
   * The {@link DispatchFactory} is used to provide singleton instances of
   * {@link NotificationDispatcher} based on a supplied type.
   */
  @Singleton
  public class DispatchFactory {
  
    /**
     * Singleton.
     */
    private static final DispatchFactory s_instance = new DispatchFactory();
  
    /**
     * Mapping of dispatch type to dispatcher singleton.
     */
    private final Map<String, NotificationDispatcher> m_dispatchers = new HashMap<>();
  
    /**
     * Constructor.
     *
     */
    private DispatchFactory() {
    }
  
    /**
     * Gets the single instance of this factory.
     *
     * @return
     */
    public static DispatchFactory getInstance() {
      return s_instance;
    }
  
    /**
     * Registers a dispatcher instance with a type.
     *
     * @param type
     *          the type
     * @param dispatcher
     *          the dispatcher to register with the type.
     */
    public void register(String type, NotificationDispatcher dispatcher) {
      if (null == dispatcher) {
        m_dispatchers.remove(type);
      } else {
        m_dispatchers.put(type, dispatcher);
      }
    }
  
    /**
     * Gets a dispatcher based on the type.
     *
     * @param type
     *          the type (not {@code null}).
     * @return a dispatcher instance, or {@code null} if none.
     */
    public NotificationDispatcher getDispatcher(String type) {
      return m_dispatchers.get(type);
    }
  }
  