/*
* 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.jena.hadoop.rdf.io.output;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.compress.CompressionCodec;
import org.apache.hadoop.io.compress.GzipCodec;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.ReflectionUtils;
import org.apache.jena.hadoop.rdf.types.AbstractNodeTupleWritable;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* An abstract implementation of an output format for line based tuple formats
* where the key is ignored and only the tuple values will be output
*
*
* @param <TKey>
* Key type
* @param <TValue>
* Tuple value type
* @param <T>
* Writable node tuple type
*
*/
public abstract class AbstractNodeTupleOutputFormat<TKey, TValue, T extends AbstractNodeTupleWritable<TValue>> extends
FileOutputFormat<TKey, T> {
private static final Logger LOG = LoggerFactory.getLogger(AbstractNodeTupleOutputFormat.class);
@Override
public RecordWriter<TKey, T> getRecordWriter(TaskAttemptContext context) throws IOException {
Configuration config = context.getConfiguration();
boolean isCompressed = getCompressOutput(context);
CompressionCodec codec = null;
// Build the output file path
String extension = this.getFileExtension();
if (isCompressed) {
// Add compression extension if applicable
Class<? extends CompressionCodec> codecClass = getOutputCompressorClass(context, GzipCodec.class);
codec = ReflectionUtils.newInstance(codecClass, config);
extension += codec.getDefaultExtension();
}
Path file = getDefaultWorkFile(context, extension);
LOG.info("Writing output to file " + file);
// Open the file appropriately and create a record writer for it
FileSystem fs = file.getFileSystem(config);
if (!isCompressed) {
FSDataOutputStream fileOut = fs.create(file, false);
return this.getRecordWriter(new OutputStreamWriter(fileOut), config, file);
} else {
FSDataOutputStream fileOut = fs.create(file, false);
return this.getRecordWriter(new OutputStreamWriter(codec.createOutputStream(fileOut)), config, file);
}
}
/**
* Gets the file extension to use for output
*
* @return File extension including the '.'
*/
protected abstract String getFileExtension();
/**
* Gets the record writer to use
*
* @param writer
* Writer to write output to
* @param config
* Configuration
* @param outputPath
* Output path being written to
* @return Record writer
* @throws IOException
* May be thrown if a record writer cannot be obtained for any
* reason
*/
protected abstract RecordWriter<TKey, T> getRecordWriter(Writer writer, Configuration config, Path outputPath)
throws IOException;
}