| /** |
| * 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 com.datatorrent.lib.db.jdbc; |
| |
| import java.sql.ResultSet; |
| import java.sql.SQLException; |
| import java.sql.Statement; |
| |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| import com.datatorrent.api.Context.OperatorContext; |
| |
| import com.datatorrent.lib.db.AbstractStoreInputOperator; |
| |
| /** |
| * This is a base implementation of a JDBC input operator. |
| * This operator reads data from a database through the JAVA DataBase Connectivity (JDBC) API |
| * and emits the data as tuples. |
| * Subclasses should implement the methods required to read the data from the database. |
| * <p> |
| * This is an abstract class. Sub-classes need to implement |
| * {@link #queryToRetrieveData()} and {@link #getTuple(ResultSet)}. |
| * </p> |
| * @displayName Abstract JDBC Input |
| * @category Input |
| * @tags database, sql |
| * |
| * @param <T> The tuple type |
| * @since 0.9.4 |
| */ |
| @org.apache.hadoop.classification.InterfaceStability.Evolving |
| public abstract class AbstractJdbcInputOperator<T> extends AbstractStoreInputOperator<T, JdbcStore> |
| { |
| private static final Logger logger = LoggerFactory.getLogger(AbstractJdbcInputOperator.class); |
| protected transient Statement queryStatement; |
| |
| /** |
| * Any concrete class has to override this method to convert a Database row into Tuple. |
| * |
| * @param result 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(ResultSet result); |
| |
| /** |
| * 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(); |
| |
| /** |
| * 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 = queryStatement.executeQuery(query); |
| if (result.next()) { |
| do { |
| T tuple = getTuple(result); |
| outputPort.emit(tuple); |
| } |
| while (result.next()); |
| } |
| } catch (SQLException ex) { |
| store.disconnect(); |
| throw new RuntimeException(String.format("Error while running query: %s", query), ex); |
| } |
| } |
| |
| @Override |
| public void setup(OperatorContext context) |
| { |
| super.setup(context); |
| try { |
| queryStatement = store.getConnection().createStatement(); |
| } catch (SQLException e) { |
| throw new RuntimeException("creating query", e); |
| } |
| } |
| } |