volker.streaming.music.lastfm.LastFmTrackFactory.java Source code

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Here is the source code for volker.streaming.music.lastfm.LastFmTrackFactory.java

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package volker.streaming.music.lastfm;

/*
 * #%L
 * NowPlaying
 * %%
 * Copyright (C) 2013 Volker Lanting
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, either version 3 of the 
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public 
 * License along with this program.  If not, see
 * <http://www.gnu.org/licenses/gpl-3.0.html>.
 * #L%
 */

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import volker.streaming.music.Track;

import com.fasterxml.jackson.databind.JsonNode;

/**
 * Java representation of the non-extended Track
 * as returned by the User.getRecentTracks API call.
 * 
 * We currently only require the following attributes:
 * <ul>
 *  <li>{@value #ARTIST}</li>
 *  <li>{@value #NAME}</li>
 *  <li>{@value #ALBUM}</li>
 * </ul>
 * <p>
 * <pre>
 * Sample JSON from the LastFM API V2.0:
 * {
 *   "artist":{"#text":"Passenger", "mbid":"186e216a-2f8a-41a1-935f-8e30c018a8fe"},
 *   "name":"Let Her Go (Peer Kusiv Edit)",
 *   "streamable":"0",
 *   "mbid":"",
 *   "album":{"#text":"","mbid":""},
 *   "url":"http:\/\/www.last.fm\/music\/Passenger\/_\/Let+Her+Go+(Peer+Kusiv+Edit)",
 *   "image":[{"#text":"","size":"small"},{"#text":"","size":"medium"},{"#text":"","size":"large"},{"#text":"","size":"extralarge"}],
 *   "@attr":{"nowplaying":"true"}
 * }
 * </pre>
 * </p>
 * @author Volker Lanting
 *
 */
public class LastFmTrackFactory {

    private static final Log LOG = LogFactory.getLog(LastFmTrackFactory.class);

    public static final String ARTIST = "artist";
    public static final String NAME = "name";
    public static final String ALBUM = "album";

    private static final String TEXT_KEY = "#text";

    /**
     * Parse a Track from a given JsonNode.
     * 
     * @param jsonTrack the JSON representation of the Track.
     * @return the Track.
     * @throws IllegalArgumentException if the jsonTrack is not valid (see {@link #isValid(JsonNode)}).
     */
    public static Track fromJson(JsonNode jsonTrack) {
        if (!isValid(jsonTrack)) {
            throw new IllegalArgumentException("Invalid json track format.");
        }
        Track track = new Track();
        track.setArtist(getTextItem(jsonTrack, ARTIST));
        track.setName(jsonTrack.get(NAME).asText());
        track.setAlbum(getTextItem(jsonTrack, ALBUM));
        return track;
    }

    // retrieve the text of the given key (see example JSON if you don't get it)
    private static String getTextItem(JsonNode track, String key) {
        return track.get(key).get(TEXT_KEY).asText();
    }

    /**
     * Check if the JSON representation of the track is valid.
     * @param track the JsonNode.
     * @return true iff the structure is valid.
     */
    public static boolean isValid(JsonNode track) {
        LOG.debug("Checking validity of track : \n" + track);
        boolean result = false;
        if (track == null)
            LOG.warn("Track is invalid: null.");
        else if (!track.hasNonNull(ARTIST))
            LOG.warn("Track is invalid: no artist attribute.");
        else if (!track.get(ARTIST).has(TEXT_KEY))
            LOG.warn("Track is invalid: artist had no text.");
        else if (!track.hasNonNull(NAME))
            LOG.warn("Track is invalid: no name attribute.");
        else if (!track.hasNonNull(ALBUM))
            LOG.warn("Track is invalid: no album attribute.");
        else if (!track.get(ALBUM).has(TEXT_KEY))
            LOG.warn("Track is invalid: album had no text.");
        else {
            result = true;
            LOG.debug("Given track is valid.");
        }
        return result;
    }

}