examples/storm-hbase-examples/src/main/java/org/apache/storm/hbase/topology/WordCountValueMapper.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.hbase.topology;

import java.util.ArrayList;
import java.util.List;
import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.CellUtil;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.storm.hbase.bolt.mapper.HBaseValueMapper;
import org.apache.storm.topology.OutputFieldsDeclarer;
import org.apache.storm.tuple.Fields;
import org.apache.storm.tuple.ITuple;
import org.apache.storm.tuple.Values;

/**
 * Takes a Hbase result and returns a value list that has a value instance for each column and corresponding value. So
 * if the result from Hbase was
 * <pre>
 * WORD, COUNT
 * apple, 10
 * bannana, 20
 * </pre>
 *
 * <p>this will return
 * <pre>
 *     [WORD, apple]
 *     [COUNT, 10]
 *     [WORD, banana]
 *     [COUNT, 20]
 * </pre>
 */
public class WordCountValueMapper implements HBaseValueMapper {

    @Override
    public List<Values> toValues(ITuple tuple, Result result) throws Exception {
        List<Values> values = new ArrayList<Values>();
        Cell[] cells = result.rawCells();
        for (Cell cell : cells) {
            Values value = new Values(Bytes.toString(CellUtil.cloneQualifier(cell)), Bytes.toLong(CellUtil.cloneValue(cell)));
            values.add(value);
        }
        return values;
    }

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

}