norbert.mynemo.dataimport.fileformat.input.MovieLensRatingImporter.java Source code

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Here is the source code for norbert.mynemo.dataimport.fileformat.input.MovieLensRatingImporter.java

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/*
 * Copyright 2015 Norbert
 *
 * 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 norbert.mynemo.dataimport.fileformat.input;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.util.Iterator;

import norbert.mynemo.dataimport.fileformat.MynemoRating;

import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVParser;
import org.apache.commons.csv.CSVRecord;

import com.google.common.collect.UnmodifiableIterator;

/**
 * This importer can parse a TSV file exported from the MovieLens web site. Such file contains the
 * ratings of only one user.
 *
 * <p>
 * Each line of the source file represents a rating. The columns are:
 * <ol>
 * <li>MovieLens id</li>
 * <li>rating value</li>
 * <li>average</li>
 * <li>IMDb id</li>
 * <li>title and year</i>
 * </ol>
 */
public class MovieLensRatingImporter implements RatingImporter {
    /**
     * Iterator over a MovieLens rating file that converts the CSV records to Mynemo ratings.
     */
    private final class RatingIterator extends UnmodifiableIterator<MynemoRating> {
        private Iterator<CSVRecord> iterator = parser.iterator();

        /**
         * Closes the parser.
         */
        private void close() {
            try {
                parser.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }

        @Override
        public boolean hasNext() {
            boolean result = iterator.hasNext();

            if (!result) {
                close();
            }

            return result;
        }

        @Override
        public MynemoRating next() {
            CSVRecord record = iterator.next();
            return new MynemoRating(user, record.get(MOVIE_INDEX), record.get(VALUE_INDEX));
        }
    }

    private static final int MOVIE_INDEX = 3;
    private static final int RECORD_SIZE = 5;
    private static final String TEST_USER = "0";
    private static final int VALUE_INDEX = 1;

    /**
     * Returns <code>true</code> if the given file can be parsed, <code>false</code> otherwise.
     */
    public static boolean canImport(String filepath) throws IOException {
        checkArgument(new File(filepath).exists(), "The file must exist.");

        if (!CleanRatingsReader.canClean(filepath)) {
            return false;
        }

        try (CSVParser parser = createParser(filepath)) {
            for (CSVRecord record : parser) {
                // try to create just one rating
                return record.size() == RECORD_SIZE
                        && MynemoRating.isValid(TEST_USER, record.get(MOVIE_INDEX), record.get(VALUE_INDEX));
            }
        }

        // everything seems right
        return true;
    }

    private static CSVParser createParser(String filepath) throws IOException {
        return new CSVParser(new CleanRatingsReader(new BufferedReader(new FileReader(filepath))), CSVFormat.MYSQL);
    }

    private final CSVParser parser;
    private final String user;

    public MovieLensRatingImporter(String filepath, String user) throws IOException {
        checkNotNull(filepath);
        checkNotNull(user);
        checkArgument(new File(filepath).exists(), "The file must exist.");

        this.user = user;
        parser = createParser(filepath);
    }

    /**
     * Returns an iterator on the ratings.
     */
    @Override
    public Iterator<MynemoRating> iterator() {
        return new RatingIterator();
    }
}