content: /*
   * 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
   *
   *     https://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.mapreduce;
  
  import java.io.IOException;
  
  import org.apache.avro.Schema;
  import org.apache.avro.mapred.AvroKey;
  import org.apache.hadoop.io.NullWritable;
  import org.apache.hadoop.mapreduce.InputSplit;
  import org.apache.hadoop.mapreduce.RecordReader;
  import org.apache.hadoop.mapreduce.TaskAttemptContext;
  import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * A MapReduce InputFormat that can handle Avro container files.
   *
   * <p>
   * Keys are AvroKey wrapper objects that contain the Avro data. Since Avro
   * container files store only records (not key/value pairs), the value from this
   * InputFormat is a NullWritable.
   * </p>
   */
  public class AvroKeyInputFormat<T> extends FileInputFormat<AvroKey<T>, NullWritable> {
    private static final Logger LOG = LoggerFactory.getLogger(AvroKeyInputFormat.class);
  
    /** {@inheritDoc} */
    @Override
    public RecordReader<AvroKey<T>, NullWritable> createRecordReader(InputSplit split, TaskAttemptContext context)
        throws IOException, InterruptedException {
      Schema readerSchema = AvroJob.getInputKeySchema(context.getConfiguration());
      if (null == readerSchema) {
        LOG.warn("Reader schema was not set. Use AvroJob.setInputKeySchema() if desired.");
        LOG.info("Using a reader schema equal to the writer schema.");
      }
      return new AvroKeyRecordReader<>(readerSchema);
    }
  }
  