source: sample/hadoop-0.17/tw/org/nchc/demo/DemoPackRecords2.java @ 20

/*
 * Cloud9: A MapReduce Library for Hadoop
 * 
 * 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 tw.org.nchc.demo;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

import org.apache.hadoop.io.Text;

import tw.org.nchc.tuple.ListWritable;
import tw.org.nchc.tuple.Schema;
import tw.org.nchc.tuple.Tuple;
import tw.org.nchc.util.LocalTupleRecordWriter;

/**
 * <p>
 * Demo that packs the sample collection into records using the tuple library,
 * illustrating the use of the {@link tw.org.nchc.tuple.Tuple} and
 * {@link tw.org.nchc.tuple.ListWritable} classes. The records are stored in
 * a local SequenceFile; this file can then be transfered over to HDFS to serve
 * as the starting point for a MapReduce operation.
 * </p>
 * 
 * <p>
 * Each record is a tuple with two fields:
 * </p>
 * 
 * <ul>
 * 
 * <li>the first field of the tuple is an Integer with the field name "length";
 * its value is the length of the record in number of characters.</li>
 * 
 * <li>the second field of the tuple is a ListWritable<Text> with the field
 * name "tokens"; its value is a list of tokens that comprise the text of the
 * record.</li>
 * 
 * </ul>
 * 
 * @see DemoPackRecords
 * @see DemoReadPackedRecords2
 */
public class DemoPackRecords2 {
  private DemoPackRecords2() {
  }

  // define the tuple schema for the input record
  private static final Schema RECORD_SCHEMA = new Schema();
  static {
    RECORD_SCHEMA.addField("length", Integer.class);
    RECORD_SCHEMA.addField("tokens", ListWritable.class, "");
  }

  // instantiate a single tuple
  private static Tuple tuple = RECORD_SCHEMA.instantiate();

  /**
   * Runs the demo.
   */
  public static void main(String[] args) throws IOException {
    String infile = "../umd-hadoop-dist/sample-input/bible+shakes.nopunc";
    String outfile = "../umd-hadoop-dist/sample-input/bible+shakes.nopunc.packed2";

    // create LocalTupleRecordWriter to write tuples to a local SequenceFile
    LocalTupleRecordWriter writer = new LocalTupleRecordWriter(outfile);

    // read in raw text records, line separated
    BufferedReader data = new BufferedReader(new InputStreamReader(
        new FileInputStream(infile)));

    String line;
    while ((line = data.readLine()) != null) {
      ListWritable<Text> tokens = new ListWritable<Text>();
      StringTokenizer itr = new StringTokenizer(line);
      while (itr.hasMoreTokens()) {
        tokens.add(new Text(itr.nextToken()));
      }

      // write the record
      tuple.set("length", line.length());
      tuple.set("tokens", tokens);
      writer.add(tuple);
    }

    data.close();
    writer.close();

    System.out.println("Wrote " + writer.getRecordCount() + " records.");
  }
}