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

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Here is the source code for org.apache.avro.mapred.DelegatingMapper.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;

/**
 * An {@link Mapper} that delegates behaviour of paths to multiple other
 * mappers. Similar to {@link HadoopMapper}, but instantiates map classes
 * in the map() call instead of during configure(), as we rely on the split
 * object to provide us that information.
 *
 * @see {@link AvroMultipleInputs#addInputPath(JobConf, Path, Class, Schema)}
 */
class DelegatingMapper<IN, OUT, K, V, KO, VO> extends MapReduceBase
        implements Mapper<AvroWrapper<IN>, NullWritable, KO, VO> {
    AvroMapper<IN, OUT> mapper;
    JobConf conf;
    boolean isMapOnly;
    AvroCollector<OUT> out;

    public void configure(JobConf conf) {
        this.conf = conf;
        this.isMapOnly = conf.getNumReduceTasks() == 0;
    }

    @Override
    public void map(AvroWrapper<IN> wrapper, NullWritable value, OutputCollector<KO, VO> collector,
            Reporter reporter) throws IOException {
        if (mapper == null) {
            TaggedInputSplit is = (TaggedInputSplit) reporter.getInputSplit();
            Class<? extends AvroMapper> mapperClass = is.getMapperClass();
            mapper = (AvroMapper<IN, OUT>) ReflectionUtils.newInstance(mapperClass, conf);
        }
        if (out == null)
            out = new MapCollector<OUT, K, V, KO, VO>(collector, isMapOnly);
        mapper.map(wrapper.datum(), out, reporter);
    }
}