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.apex.malhar.contrib.aerospike;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import org.apache.apex.malhar.lib.db.AbstractStoreInputOperator;
  
  import com.aerospike.client.Record;
  import com.aerospike.client.query.RecordSet;
  import com.aerospike.client.query.Statement;
  import com.datatorrent.api.DefaultOutputPort;
  import com.datatorrent.netlet.util.DTThrowable;
  
  /**
   * Base input adapter, which reads data from persistence database through its
   * API and writes into output port(s). Subclasses should provide the
   * implementation of getting the tuples and querying to retrieve data.
   * <p>
   * This is an abstract class. Sub-classes need to implement
   * {@link #queryToRetrieveData()} and {@link #getTuple(Record)}.
   *
   * @displayName Abstract Aerospike Get
   * @category Input
   * @tags get
   * @since 1.0.4
   */
  public abstract class AbstractAerospikeGetOperator<T> extends AbstractStoreInputOperator<T, AerospikeStore>
  {
    private static final Logger logger = LoggerFactory.getLogger(AbstractAerospikeGetOperator.class);
  
    /**
     * Any concrete class has to override this method to convert a Database row into Tuple.
     *
     * @param row a single row that has been read from database.
     * @return Tuple a tuples created from row which can be any Java object.
     */
    public abstract T getTuple(Record record);
  
    /**
     * Any concrete class has to override this method to return the query string which will be used to
     * retrieve data from database.
     *
     * @return Query string
     */
    public abstract Statement queryToRetrieveData();
  
    /**
     * The output port that will emit tuple into DAG.
     */
    public final transient DefaultOutputPort<T> outputPort = new DefaultOutputPort<T>();
  
    /**
     * This executes the query to retrieve result from database.
     * It then converts each row into tuple and emit that into output port.
     */
    @Override
    public void emitTuples()
    {
      Statement query = queryToRetrieveData();
      logger.debug(String.format("select statement: %s", query.toString()));
      RecordSet rs;
      try {
        rs = store.getClient().query(null, query);
        while (rs.next()) {
          Record rec = rs.getRecord();
          T tuple = getTuple(rec);
          outputPort.emit(tuple);
        }
      } catch (Exception ex) {
        store.disconnect();
        DTThrowable.rethrow(ex);
      }
    }
  }
  