contrib/src/main/java/com/datatorrent/contrib/aerospike/AbstractAerospikeGetOperator.java

/*
 * Copyright (c) 2014 DataTorrent, Inc. ALL Rights Reserved.
 *
 * Licensed 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 com.datatorrent.contrib.aerospike;


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.common.util.DTThrowable;
import com.datatorrent.lib.db.AbstractStoreInputOperator;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Base input adapter, which reads data from persistence database through its API and writes into output port(s).&nsbsp;
 * 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)}.
 * </p>
 * @displayName Abstract Aerospike Get
 * @category Database
 * @tags get, input operator
 * @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);
    }
  }
}