| /* |
| * 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.cassandra; |
| |
| |
| import com.datastax.driver.core.ResultSet; |
| import com.datastax.driver.core.Row; |
| import com.datatorrent.api.DefaultOutputPort; |
| import com.datatorrent.api.annotation.OutputPortFieldAnnotation; |
| import com.datatorrent.api.annotation.ShipContainingJars; |
| import com.datatorrent.common.util.DTThrowable; |
| import com.datatorrent.lib.db.AbstractStoreInputOperator; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| /** |
| * Base Cassandra input adapter operator, which reads data from persistence database through DATASTAX API |
| * and writes into output port(s). |
| * |
| * <p> |
| * This is an abstract class. Sub-classes need to implement {@link #queryToRetrieveData()} and {@link #getTuple(Row)}. |
| * </p> |
| */ |
| @ShipContainingJars(classes = {com.datastax.driver.core.Cluster.class}) |
| |
| public abstract class AbstractCassandraInputOperator<T> extends AbstractStoreInputOperator<T, CassandraStore> { |
| |
| private static final Logger logger = LoggerFactory.getLogger(AbstractCassandraInputOperator.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(Row row); |
| |
| /** |
| * 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 String queryToRetrieveData(); |
| |
| /** |
| * The output port that will emit tuple into DAG. |
| */ |
| @OutputPortFieldAnnotation(name = "outputPort") |
| 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() |
| { |
| String query = queryToRetrieveData(); |
| logger.debug(String.format("select statement: %s", query)); |
| |
| try { |
| ResultSet result = store.getSession().execute(query); |
| for(Row row: result) { |
| T tuple = getTuple(row); |
| outputPort.emit(tuple); |
| } |
| } |
| catch (Exception ex) { |
| store.disconnect(); |
| DTThrowable.rethrow(ex); |
| } |
| } |
| } |