org.apache.avro.mapred.HadoopMapper.java Source code

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Here is the source code for org.apache.avro.mapred.HadoopMapper.java

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/**
 * 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.avro.mapred;

import java.io.IOException;

import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.util.ReflectionUtils;

/** Bridge between a {@link org.apache.hadoop.mapred.Mapper} and an {@link
 * AvroMapper}.  Outputs are written directly when a job is map-only, but are
 * otherwise assumed to be pairs that are split. */
class HadoopMapper<IN, OUT, K, V, KO, VO> extends MapReduceBase
        implements Mapper<AvroWrapper<IN>, NullWritable, KO, VO> {

    private AvroMapper<IN, OUT> mapper;
    private MapCollector out;
    private boolean isMapOnly;

    @Override
    @SuppressWarnings("unchecked")
    public void configure(JobConf conf) {
        this.mapper = ReflectionUtils.newInstance(conf.getClass(AvroJob.MAPPER, AvroMapper.class, AvroMapper.class),
                conf);
        this.isMapOnly = conf.getNumReduceTasks() == 0;
    }

    @SuppressWarnings("unchecked")
    private class MapCollector extends AvroCollector<OUT> {
        private final AvroWrapper<OUT> wrapper = new AvroWrapper<OUT>(null);
        private final AvroKey<K> keyWrapper = new AvroKey(null);
        private final AvroValue<V> valueWrapper = new AvroValue(null);
        private OutputCollector<KO, VO> collector;

        public MapCollector(OutputCollector<KO, VO> collector) {
            this.collector = collector;
        }

        public void collect(OUT datum) throws IOException {
            if (isMapOnly) {
                wrapper.datum(datum);
                collector.collect((KO) wrapper, (VO) NullWritable.get());
            } else { // split a pair
                Pair<K, V> pair = (Pair<K, V>) datum;
                keyWrapper.datum(pair.key());
                valueWrapper.datum(pair.value());
                collector.collect((KO) keyWrapper, (VO) valueWrapper);
            }
        }
    }

    @Override
    public void map(AvroWrapper<IN> wrapper, NullWritable value, OutputCollector<KO, VO> collector,
            Reporter reporter) throws IOException {
        if (this.out == null)
            this.out = new MapCollector(collector);
        mapper.map(wrapper.datum(), out, reporter);
    }

    @Override
    public void close() throws IOException {
        this.mapper.close();
    }

}