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.activemq.broker.view;
  
  import java.util.HashMap;
  import java.util.Map;
  
  import org.apache.activemq.broker.BrokerRegistry;
  import org.apache.activemq.broker.BrokerService;
  
  public class MessageBrokerViewRegistry {
  
      private static final MessageBrokerViewRegistry INSTANCE = new MessageBrokerViewRegistry();
  
      private final Object mutex = new Object();
      private final Map<String, MessageBrokerView> brokerViews = new HashMap<String, MessageBrokerView>();
  
      public static MessageBrokerViewRegistry getInstance() {
          return INSTANCE;
      }
  
      /**
       * @param brokerName
       * @return the BrokerService
       */
      public MessageBrokerView lookup(String brokerName) {
          MessageBrokerView result = null;
          synchronized (mutex) {
              result = brokerViews.get(brokerName);
              if (result==null){
                  BrokerService brokerService = BrokerRegistry.getInstance().lookup(brokerName);
                  if (brokerService != null){
                      result = new MessageBrokerView(brokerService);
                      brokerViews.put(brokerName,result);
                  }
              }
  
          }
          return result;
      }
  }
  