text: /**
   * 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.hadoop.fs.slive;
  
  import java.util.List;
  
  import org.apache.hadoop.fs.FileSystem;
  
  /**
   * Operation which wraps a given operation and allows an observer to be notified
   * when the operation is about to start and when the operation has finished
   */
  class ObserveableOp extends Operation {
  
    /**
     * The observation interface which class that wish to monitor starting and
     * ending events must implement.
     */
    interface Observer {
      void notifyStarting(Operation op);
      void notifyFinished(Operation op);
    }
  
    private Operation op;
    private Observer observer;
  
    ObserveableOp(Operation op, Observer observer) {
      super(op.getType(), op.getConfig(), op.getRandom());
      this.op = op;
      this.observer = observer;
    }
  
    /**
     * Proxy to underlying operation toString()
     */
    public String toString() {
      return op.toString();
    }
  
    @Override // Operation
    List<OperationOutput> run(FileSystem fs) {
      List<OperationOutput> result = null;
      try {
        if (observer != null) {
          observer.notifyStarting(op);
        }
        result = op.run(fs);
      } finally {
        if (observer != null) {
          observer.notifyFinished(op);
        }
      }
      return result;
    }
  
  }
  