contrib/bolts/kafka/src/java/org/apache/heron/bolts/kafka/TupleTransformer.java

/**
 * 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.bolts.kafka;

import java.io.Serializable;

import org.apache.heron.api.tuple.Tuple;

public interface TupleTransformer<K, V> extends Serializable {

  default K transformToKey(Tuple tuple) {
    if (tuple.contains("key")) {
      //noinspection unchecked
      return (K) tuple.getValueByField("key");
    }
    return null;
  }

  default V transformToValue(Tuple tuple) {
    if (tuple.contains("value")) {
      //noinspection unchecked
      return (V) tuple.getValueByField("value");
    }
    return null;
  }

  String getTopicName(Tuple tuple);
}