joshelser.as2015.parser.AmazonReviewParser.java Source code

Introduction

Here is the source code for joshelser.as2015.parser.AmazonReviewParser.java

Source

/*
 * 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 joshelser.as2015.parser;

import java.io.BufferedReader;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.util.Iterator;

import org.apache.commons.lang.StringUtils;

/**
 * Parses reviews scraped from Amazon obtained from https://snap.stanford.edu/data/web-Amazon.html
 */
public class AmazonReviewParser implements Iterator<AmazonReview> {

    private final BufferedReader reader;
    private boolean readerExhausted = false;
    private AmazonReview currentReview = null;

    public AmazonReviewParser(BufferedReader reader) {
        this.reader = reader;
        currentReview = getNextReview();
    }

    @Override
    public AmazonReview next() {
        AmazonReview prevReview = currentReview;
        currentReview = getNextReview();
        return prevReview;
    }

    @Override
    public boolean hasNext() {
        return null != currentReview;
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException("remove is not supported");
    }

    /**
     * Compute the next review from the reader.
     * 
     * @return The next review or null if there is none
     */
    AmazonReview getNextReview() {
        if (readerExhausted) {
            return null;
        }

        try {
            String line;
            AmazonReview nextReview = null;
            do {
                line = reader.readLine();
                if (null == line) {
                    readerExhausted = true;
                    return nextReview;
                }

                // Empty line is message separator
                if (StringUtils.isBlank(line)) {
                    // If we have a review return it
                    if (null != nextReview) {
                        return nextReview;
                    }
                    // otherwise, just try to read the next message
                } else {
                    if (null == nextReview) {
                        nextReview = new AmazonReview();
                    }
                    int index = line.indexOf(':');
                    if (-1 == index) {
                        throw new IllegalArgumentException("Cannot parse line '" + line + "'");
                    }
                    String key = StringUtils.strip(line.substring(0, index));
                    String value = StringUtils.strip(line.substring(index + 1));

                    index = key.indexOf('/');
                    if (-1 == index) {
                        throw new IllegalArgumentException("Cannot parse key '" + key + "'");
                    }
                    AmazonReviewField field = new AmazonReviewField(key.substring(0, index),
                            key.substring(index + 1));
                    nextReview.addReviewField(field, ByteBuffer.wrap(value.getBytes(StandardCharsets.UTF_8)));
                }
            } while (!readerExhausted);
            return nextReview;
        } catch (IOException e) {
            throw new RuntimeException("Failed to read file", e);
        }
    }
}