co.nubetech.hiho.mapreduce.lib.output.NoKeyOnlyValueOutputFormat.java Source code

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Here is the source code for co.nubetech.hiho.mapreduce.lib.output.NoKeyOnlyValueOutputFormat.java

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/**
 * Copyright 2010 Nube Technologies
 * 
 * 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 co.nubetech.hiho.mapreduce.lib.output;

import java.io.DataOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;

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.Text;
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;

/**
 * This class ignores the key and simply prints the value. However, new line is
 * added
 * 
 * @author sgoyal
 * 
 */
public class NoKeyOnlyValueOutputFormat<K, V> extends FileOutputFormat<K, V> {

    protected static class NoKeyRecordWriter<K, V> extends RecordWriter<K, V> {
        private static final String utf8 = "UTF-8";

        private static final byte[] newline;
        static {
            try {
                newline = "\n".getBytes(utf8);
            } catch (UnsupportedEncodingException uee) {
                throw new IllegalArgumentException("can't find " + utf8 + " encoding");
            }
        }

        protected DataOutputStream out;

        public NoKeyRecordWriter(DataOutputStream out) {
            this.out = out;
        }

        /**
         * Write the object to the byte stream, handling Text as a special case.
         * 
         * @param o
         *            the object to print
         * @throws IOException
         *             if the write throws, we pass it on
         */
        private void writeObject(Object o) throws IOException {
            if (o instanceof Text) {
                Text to = (Text) o;
                out.write(to.getBytes(), 0, to.getLength());
            } else {
                out.write(o.toString().getBytes(utf8));
            }
        }

        public synchronized void write(K key, V value) throws IOException {
            writeObject(value);
            out.write(newline);
        }

        public synchronized void close(TaskAttemptContext context) throws IOException {
            out.close();
        }
    }

    public RecordWriter<K, V> getRecordWriter(TaskAttemptContext context) throws IOException {
        boolean isCompressed = getCompressOutput(context);
        Configuration conf = context.getConfiguration();
        String ext = "";
        CompressionCodec codec = null;

        if (isCompressed) {
            // create the named codec
            Class<? extends CompressionCodec> codecClass = getOutputCompressorClass(context, GzipCodec.class);
            codec = ReflectionUtils.newInstance(codecClass, conf);

            ext = codec.getDefaultExtension();
        }

        Path file = getDefaultWorkFile(context, ext);
        FileSystem fs = file.getFileSystem(conf);
        FSDataOutputStream fileOut = fs.create(file, false);
        DataOutputStream ostream = fileOut;

        if (isCompressed) {
            ostream = new DataOutputStream(codec.createOutputStream(fileOut));
        }

        return new NoKeyRecordWriter<K, V>(ostream);
    }
}