storm-client/src/jvm/org/apache/storm/lambda/LambdaSpout.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
 *
 * 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 org.apache.storm.lambda;

import java.util.Map;
import org.apache.storm.spout.SpoutOutputCollector;
import org.apache.storm.task.TopologyContext;
import org.apache.storm.topology.OutputFieldsDeclarer;
import org.apache.storm.topology.base.BaseRichSpout;
import org.apache.storm.tuple.Fields;
import org.apache.storm.tuple.Values;

public class LambdaSpout extends BaseRichSpout {
    private SerializableSupplier<?> supplier;
    private SpoutOutputCollector collector;

    public LambdaSpout(SerializableSupplier<?> supplier) {
        this.supplier = supplier;
    }

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

    @Override
    public void nextTuple() {
        Object obj = supplier.get();
        if (obj != null) {
            collector.emit(new Values(obj));
        }
    }

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