CustomSpout.java

// Copyright 2016 Twitter. 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.twitter.heron.integration_test.topology.serialization;

import java.util.Map;

import com.twitter.heron.api.spout.BaseRichSpout;
import com.twitter.heron.api.spout.SpoutOutputCollector;
import com.twitter.heron.api.topology.OutputFieldsDeclarer;
import com.twitter.heron.api.topology.TopologyContext;
import com.twitter.heron.api.tuple.Fields;
import com.twitter.heron.api.tuple.Values;

/**
 * A spout that emits two different custom objects continuously in order,
 * one object every "nextTuple()" called
 * Note that CustomObject uses Java serialization
 */
public class CustomSpout extends BaseRichSpout {
  private static final long serialVersionUID = -5906196959214294058L;
  private SpoutOutputCollector collector;
  private int emitted = 0;
  private CustomObject[] inputObjects;

  public CustomSpout(CustomObject[] inputObjects) {
    this.inputObjects = inputObjects;
  }

  @Override
  public void open(Map<String, Object> conf,
                   TopologyContext context,
                   SpoutOutputCollector outputCollector) {
    this.collector = outputCollector;
  }

  @Override
  public void nextTuple() {
    CustomObject obj = inputObjects[(emitted++) % inputObjects.length];
    collector.emit(new Values(obj));
  }

  @Override
  public void declareOutputFields(OutputFieldsDeclarer declarer) {
    declarer.declare(new Fields("custom"));
  }
}