WikipediaToItemPrefsMapper.java

package org.mahout.recommendations.wikipedia;

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.mahout.math.VarLongWritable;

import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Download wikipedia related link data from here:
 * http://users.on.net/%7Ehenry/pagerank/links-simple-sorted.zip
 *
 * @author Krisztian_Horvath
 */
public class WikipediaToItemPrefsMapper extends Mapper<LongWritable, Text, VarLongWritable, VarLongWritable> {

    private static final Pattern NUMBERS = Pattern.compile("(\\d+)");

    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        String line = value.toString();
        Matcher m = NUMBERS.matcher(line);
        m.find();
        VarLongWritable userID = new VarLongWritable(Long.parseLong(m.group()));
        VarLongWritable itemID = new VarLongWritable();
        while (m.find()) {
            itemID.set(Long.parseLong(m.group()));
            context.write(userID, itemID);
        }
    }
}