/**
 * 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.hadoop.mapred;

import java.io.IOException;

import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.util.ReflectionUtils;

/** Default {@link MapRunnable} implementation.*/
public class MapRunner implements MapRunnable {
  private Mapper mapper;

  public void configure(JobConf job) {
    this.mapper = (Mapper)ReflectionUtils.newInstance(job.getMapperClass(),
                                                      job);
  }

  public void run(RecordReader input, OutputCollector output,
                  Reporter reporter)
    throws IOException {
    try {
      // allocate key & value instances that are re-used for all entries
      WritableComparable key = input.createKey();
      Writable value = input.createValue();
      
      while (input.next(key, value)) {
        // map pair to output
        mapper.map(key, value, output, reporter);
      }
    } finally {
      mapper.close();
    }
  }

}
