external/flux/flux-examples/src/main/java/org/apache/storm/flux/examples/StatefulWordCounter.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.flux.examples;

import org.apache.storm.state.KeyValueState;
import org.apache.storm.task.OutputCollector;
import org.apache.storm.task.TopologyContext;
import org.apache.storm.topology.base.BaseStatefulBolt;
import org.apache.storm.topology.OutputFieldsDeclarer;
import org.apache.storm.tuple.Fields;
import org.apache.storm.tuple.Tuple;
import org.apache.storm.tuple.Values;

import java.util.Map;

public class StatefulWordCounter extends BaseStatefulBolt<KeyValueState<String, Long>> {

    private KeyValueState<String, Long> wordCounts;
    private OutputCollector collector;

    @SuppressWarnings("rawtypes")
    @Override
    public void prepare(Map stormConf, TopologyContext context, OutputCollector collector) {
        this.collector = collector;
    }

    @Override
    public void initState(KeyValueState<String, Long> state) {
        wordCounts = state;
    }

    @Override
    public void execute(Tuple tuple) {
        String word = tuple.getString(0);

        Long count = wordCounts.get(word, 0L);
        count++;
        wordCounts.put(word, count);

        collector.emit(tuple, new Values(word, count));
        collector.ack(tuple);
    }

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