format.WikipediaPageInputFormat.java Source code

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Here is the source code for format.WikipediaPageInputFormat.java

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/*
 * 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 format;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.LongWritable;
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 format.XMLInputFormat.XMLRecordReader;
import edu.umd.cloud9.collection.wikipedia.WikipediaPage;

/**
 * To replace WikipediaPageInputFormat from cloud9 to work with hadoop 2.0
 * @author Tuan
 *
 */
public class WikipediaPageInputFormat extends IndexableFileInputFormat<LongWritable, WikipediaPage> {

    @Override
    public RecordReader<LongWritable, WikipediaPage> createRecordReader(InputSplit split,
            TaskAttemptContext context) throws IOException, InterruptedException {
        context.setStatus(split.toString());
        return new WikipediaPageRecordReader(context.getConfiguration());
    }

    /**
     * Hadoop <code>RecordReader</code> for reading Wikipedia pages from the XML
     * dumps.
     */
    public static class WikipediaPageRecordReader extends RecordReader<LongWritable, WikipediaPage> {
        private XMLRecordReader reader;
        private Text text = new Text();
        private LongWritable offset = new LongWritable();
        LongWritable key;
        WikipediaPage value;

        /**
         * Creates a <code>WikipediaPageRecordReader</code>.
         * 
         * @throws InterruptedException
         */
        public WikipediaPageRecordReader(Configuration conf) throws IOException, InterruptedException {
            conf.set(XMLInputFormat.START_TAG_KEY, WikipediaPage.XML_START_TAG);
            conf.set(XMLInputFormat.END_TAG_KEY, WikipediaPage.XML_END_TAG);
        }

        /**
         * Creates an object for the key.
         */
        public LongWritable createKey() {
            return new LongWritable();
        }

        /**
         * Creates an object for the value.
         */
        public WikipediaPage createValue() {
            return new WikipediaPage();
        }

        /**
         * Returns the current position in the input.
         */
        public long getPos() throws IOException {
            return reader.getPos();
        }

        /**
         * Closes this InputSplit.
         */
        public void close() throws IOException {
            reader.close();
        }

        /**
         * Returns progress on how much input has been consumed.
         */
        public float getProgress() throws IOException {
            return ((float) (reader.getPos() - reader.getStart()))
                    / ((float) (reader.getEnd() - reader.getStart()));
        }

        @Override
        public LongWritable getCurrentKey() throws IOException, InterruptedException {
            return key;
        }

        @Override
        public WikipediaPage getCurrentValue() throws IOException, InterruptedException {
            return value;
        }

        @Override
        public void initialize(InputSplit split, TaskAttemptContext context)
                throws IOException, InterruptedException {
            reader = new XMLRecordReader(split, context);
        }

        @Override
        public boolean nextKeyValue() throws IOException, InterruptedException {
            // Get next key value
            if (reader.nextKeyValue() == false)
                return false;
            offset = reader.getCurrentKey();
            text = reader.getCurrentValue();

            if (key == null) {
                key = new LongWritable();
            }
            if (value == null) {
                value = new WikipediaPage();
            }
            key.set(offset.get());
            WikipediaPage.readPage(value, text.toString());
            return true;
        }
    }

}