| /** |
| * 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 |
| * <p> |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * <p> |
| * 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.heron.spouts.kafka; |
| |
| import java.io.Serializable; |
| import java.util.Arrays; |
| import java.util.Collections; |
| import java.util.List; |
| import java.util.Map; |
| |
| import org.apache.kafka.clients.consumer.ConsumerRecord; |
| |
| /** |
| * This is the transformer class whose responsibility is to: |
| * |
| * <ol> |
| * <li>define the id of the output streams</li> |
| * <li>declare the list of fields of the output tuple</li> |
| * <li>translate the incoming Kafka record into the list of values of the output tuple</li> |
| * </ol> |
| * <p> |
| * The default behavior of the built-in transformer will output to stream "default", |
| * with 2 fields, "key" and "value" which are the key and value field of the incoming Kafka record. |
| * |
| * @param <K> the type of the key of the Kafka record |
| * @param <V> the type of the value of the Kafka record |
| * @see KafkaSpout#setConsumerRecordTransformer(ConsumerRecordTransformer) |
| */ |
| public interface ConsumerRecordTransformer<K, V> extends Serializable { |
| default List<String> getOutputStreams() { |
| return Collections.singletonList("default"); |
| } |
| |
| default List<String> getFieldNames(String streamId) { |
| return Arrays.asList("key", "value"); |
| } |
| |
| default Map<String, List<Object>> transform(ConsumerRecord<K, V> record) { |
| return Collections.singletonMap("default", Arrays.asList(record.key(), record.value())); |
| } |
| } |