/**
* 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;
import org.apache.hadoop.util.ReflectionUtils;
/** 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)ReflectionUtils.newInstance(job.getMapperClass(),
job);
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)ReflectionUtils.newInstance(inputKeyClass, job);
Writable value = (Writable)ReflectionUtils.newInstance(inputValueClass,
job);
while (input.next(key, value)) {
// map pair to output
mapper.map(key, value, output, reporter);
}
} finally {
mapper.close();
}
}
}