/** * Copyright 2005 The Apache Software Foundation * * Licensed 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;/** Default {@link MapRunnable} implementation.*/public class MapRunner implements MapRunnable {  private JobConf job;  private Mapper mapper;  private Class inputKeyClass;  private Class inputValueClass;  public void configure(JobConf job) {    this.job = job;    this.mapper = (Mapper)job.newInstance(job.getMapperClass());    this.inputKeyClass = job.getInputKeyClass();    this.inputValueClass = job.getInputValueClass();  }  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 =        (WritableComparable)job.newInstance(inputKeyClass);      Writable value = (Writable)job.newInstance(inputValueClass);      while (input.next(key, value)) {        // map pair to output        mapper.map(key, value, output, reporter);      }    } finally {        mapper.close();    }  }}