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Apache Hadoop MapReduce Streaming
/**
* 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.streaming.mapreduce;
import java.io.IOException;
import java.lang.reflect.Constructor;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.io.Text;
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.FileSplit;
import org.apache.hadoop.mapreduce.lib.input.KeyValueTextInputFormat;
import org.apache.hadoop.streaming.StreamUtil;
/**
* An input format that selects a RecordReader based on a JobConf property. This
* should be used only for non-standard record reader such as
* StreamXmlRecordReader. For all other standard record readers, the appropriate
* input format classes should be used.
*/
public class StreamInputFormat extends KeyValueTextInputFormat {
@Override
public RecordReader createRecordReader(InputSplit genericSplit,
TaskAttemptContext context) throws IOException {
Configuration conf = context.getConfiguration();
String c = conf.get("stream.recordreader.class");
if (c == null || c.indexOf("LineRecordReader") >= 0) {
return super.createRecordReader(genericSplit, context);
}
// handling non-standard record reader (likely StreamXmlRecordReader)
FileSplit split = (FileSplit) genericSplit;
// LOG.info("getRecordReader start.....split=" + split);
context.setStatus(split.toString());
context.progress();
// Open the file and seek to the start of the split
FileSystem fs = split.getPath().getFileSystem(conf);
FSDataInputStream in = fs.open(split.getPath());
// Factory dispatch based on available params..
Class readerClass;
{
readerClass = StreamUtil.goodClassOrNull(conf, c, null);
if (readerClass == null) {
throw new RuntimeException("Class not found: " + c);
}
}
Constructor ctor;
try {
ctor = readerClass.getConstructor(new Class[] { FSDataInputStream.class,
FileSplit.class, TaskAttemptContext.class, Configuration.class,
FileSystem.class });
} catch (NoSuchMethodException nsm) {
throw new RuntimeException(nsm);
}
RecordReader reader;
try {
reader = (RecordReader) ctor.newInstance(new Object[] { in,
split, context, conf, fs });
} catch (Exception nsm) {
throw new RuntimeException(nsm);
}
return reader;
}
}