X-Git-Url: https://git.pterodactylus.net/?a=blobdiff_plain;f=src%2Fmain%2Fjava%2Fnet%2Fpterodactylus%2Fdemoscenemusic%2Fdata%2FDataManager.java;h=f3d35788f2cfaee5af00bef82ef0c4a78227debb;hb=51130ce0f519aa3ac648999413e76558679ee182;hp=7943401609d28f8a975d32584af2773c13057023;hpb=5f372a5ff952630d8297cfc01d5d2ba1b83a0295;p=demoscenemusic.git

diff --git a/src/main/java/net/pterodactylus/demoscenemusic/data/DataManager.java b/src/main/java/net/pterodactylus/demoscenemusic/data/DataManager.java
index 7943401..f3d3578 100644
--- a/src/main/java/net/pterodactylus/demoscenemusic/data/DataManager.java
+++ b/src/main/java/net/pterodactylus/demoscenemusic/data/DataManager.java
@@ -38,6 +38,7 @@ import net.pterodactylus.util.database.Join.JoinType;
 import net.pterodactylus.util.database.ObjectCreator;
 import net.pterodactylus.util.database.ObjectCreator.StringCreator;
 import net.pterodactylus.util.database.OrderField;
+import net.pterodactylus.util.database.Parameter.IntegerParameter;
 import net.pterodactylus.util.database.Parameter.StringParameter;
 import net.pterodactylus.util.database.Query;
 import net.pterodactylus.util.database.Query.Type;
@@ -72,6 +73,10 @@ public class DataManager {
 	@SuppressWarnings("synthetic-access")
 	private final ObjectCreator<Style> styleCreator = new StyleCreator();
 
+	/** The party object creator. */
+	@SuppressWarnings("synthetic-access")
+	private final ObjectCreator<Party> partyCreator = new PartyCreator();
+
 	/** The {@link User} object creator. */
 	@SuppressWarnings("synthetic-access")
 	private final ObjectCreator<User> userCreator = new UserCreator();
@@ -99,7 +104,7 @@ public class DataManager {
 	public Collection<Artist> getAllArtists() throws DatabaseException {
 		Query query = new Query(Type.SELECT, "ARTISTS");
 		query.addField(new Field("ARTISTS.*"));
-		return loadProperties(database.getMultiple(query, artistCreator));
+		return loadArtistProperties(database.getMultiple(query, artistCreator));
 	}
 
 	/**
@@ -116,7 +121,7 @@ public class DataManager {
 		Query query = new Query(Type.SELECT, "ARTISTS");
 		query.addField(new Field("ARTISTS.*"));
 		query.addWhereClause(new ValueFieldWhereClause(new ValueField("ARTISTS.ID", new StringParameter(id))));
-		return loadProperties(database.getSingle(query, artistCreator));
+		return loadArtistProperties(database.getSingle(query, artistCreator));
 	}
 
 	/**
@@ -133,7 +138,7 @@ public class DataManager {
 		query.addField(new Field("ARTISTS.*"));
 		query.addJoin(new Join(JoinType.INNER, "GROUP_ARTISTS", new Field("ARTISTS.ID"), new Field("GROUP_ARTISTS.ARTIST")));
 		query.addWhereClause(new ValueFieldWhereClause(new ValueField("GROUP_ARTISTS.GROUP_", new StringParameter(groupId))));
-		return loadProperties(database.getMultiple(query, artistCreator));
+		return loadArtistProperties(database.getMultiple(query, artistCreator));
 	}
 
 	/**
@@ -151,7 +156,7 @@ public class DataManager {
 		query.addJoin(new Join(JoinType.INNER, "TRACK_ARTISTS", new Field("TRACK_ARTISTS.ARTIST"), new Field("ARTISTS.ID")));
 		query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_ARTISTS.TRACK", new StringParameter(trackId))));
 		query.addOrderField(new OrderField(new Field("TRACK_ARTISTS.DISPLAY_ORDER")));
-		return loadProperties(database.getMultiple(query, artistCreator));
+		return loadArtistProperties(database.getMultiple(query, artistCreator));
 	}
 
 	/**
@@ -169,7 +174,7 @@ public class DataManager {
 		query.addValueField(new ValueField("ID", new StringParameter(id)));
 		query.addValueField(new ValueField("NAME", new StringParameter(name)));
 		database.insert(query);
-		return loadProperties(getArtistById(id));
+		return loadArtistProperties(getArtistById(id));
 	}
 
 	/**
@@ -240,23 +245,8 @@ public class DataManager {
 	 * @throws DatabaseException
 	 *             if a database error occurs
 	 */
-	public Artist loadProperties(final Artist artist) throws DatabaseException {
-		Query query = new Query(Type.SELECT, "ARTIST_PROPERTIES");
-		query.addField(new Field("ARTIST_PROPERTIES.PROPERTY"));
-		query.addField(new Field("ARTIST_PROPERTIES.VALUE"));
-		query.addWhereClause(new ValueFieldWhereClause(new ValueField("ARTIST", new StringParameter(artist.getId()))));
-		database.process(query, new ResultProcessor() {
-
-			@Override
-			public void processResult(ResultSet resultSet) throws SQLException {
-				if (resultSet.isFirst()) {
-					artist.getProperties().removeAll();
-				}
-				artist.getProperties().set(resultSet.getString("ARTIST_PROPERTIES.PROPERTY"), resultSet.getString("ARTIST_PROPERTIES.VALUE"));
-			}
-
-		});
-		return artist;
+	public Artist loadArtistProperties(final Artist artist) throws DatabaseException {
+		return loadProperties(artist, "ARTIST_PROPERTIES", "ARTIST");
 	}
 
 	/**
@@ -268,9 +258,9 @@ public class DataManager {
 	 * @throws DatabaseException
 	 *             if a database error occurs
 	 */
-	public List<Artist> loadProperties(List<Artist> artists) throws DatabaseException {
+	public List<Artist> loadArtistProperties(List<Artist> artists) throws DatabaseException {
 		for (Artist artist : artists) {
-			loadProperties(artist);
+			loadArtistProperties(artist);
 		}
 		return artists;
 	}
@@ -339,7 +329,25 @@ public class DataManager {
 		Query query = new Query(Type.SELECT, "TRACKS");
 		query.addField(new Field("TRACKS.*"));
 		query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACKS.ID", new StringParameter(id))));
-		return database.getSingle(query, trackCreator);
+		return loadTrackProperties(database.getSingle(query, trackCreator));
+	}
+
+	/**
+	 * Returns the track that contains the derivative with the given ID.
+	 *
+	 * @param id
+	 *            The ID of the track derivative
+	 * @return The track the derivative belongs to, or {@code null} if there is
+	 *         no such track
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public Track getTrackByDerivativeId(String id) throws DatabaseException {
+		Query query = new Query(Type.SELECT, "TRACKS");
+		query.addField(new Field("TRACKS.*"));
+		query.addJoin(new Join(JoinType.INNER, "TRACK_DERIVATIVES", new Field("TRACK_DERIVATIVES.TRACK"), new Field("TRACKS.ID")));
+		query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_DERIVATIVES.ID", new StringParameter(id))));
+		return loadTrackProperties(database.getSingle(query, trackCreator));
 	}
 
 	/**
@@ -356,7 +364,223 @@ public class DataManager {
 		query.addField(new Field("TRACKS.*"));
 		query.addJoin(new Join(JoinType.INNER, "TRACK_ARTISTS", new Field("TRACKS.ID"), new Field("TRACK_ARTISTS.TRACK")));
 		query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_ARTISTS.ARTIST", new StringParameter(artistId))));
-		return database.getMultiple(query, trackCreator);
+		return loadTrackProperties(database.getMultiple(query, trackCreator));
+	}
+
+	/**
+	 * Returns all tracks that were released at the party with the given ID.
+	 *
+	 * @param partyId
+	 *            The ID of the party
+	 * @return All tracks that were released at the given party
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public Collection<Track> getTracksByParty(String partyId) throws DatabaseException {
+		Query query = new Query(Type.SELECT, "TRACKS");
+		query.addField(new Field("TRACKS.*"));
+		query.addJoin(new Join(JoinType.INNER, "PARTY_TRACKS", new Field("PARTY_TRACKS.TRACK"), new Field("TRACKS.ID")));
+		query.addWhereClause(new ValueFieldWhereClause(new ValueField("PARTY_TRACKS.PARTY", new StringParameter(partyId))));
+		return loadTrackProperties(database.getMultiple(query, trackCreator));
+	}
+
+	/**
+	 * Loads the properties for the given track.
+	 *
+	 * @param track
+	 *            The track for which to load the properties
+	 * @return The track with the properties loaded
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public Track loadTrackProperties(Track track) throws DatabaseException {
+		return loadProperties(track, "TRACK_PROPERTIES", "TRACK");
+	}
+
+	/**
+	 * Loads the properties for the given tracks.
+	 *
+	 * @param tracks
+	 *            The tracks for which to load the properties
+	 * @return The tracks with the properties loaded
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public List<Track> loadTrackProperties(List<Track> tracks) throws DatabaseException {
+		for (Track track : tracks) {
+			loadTrackProperties(track);
+		}
+		return tracks;
+	}
+
+	/**
+	 * Creates a new track with the given name.
+	 *
+	 * @param name
+	 *            The name of the track
+	 * @return The created track
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public Track createTrack(String name) throws DatabaseException {
+		Query query = new Query(Type.INSERT, "TRACKS");
+		String id = UUID.randomUUID().toString();
+		query.addValueField(new ValueField("ID", new StringParameter(id)));
+		query.addValueField(new ValueField("NAME", new StringParameter(name)));
+		database.insert(query);
+		return getTrackById(id);
+	}
+
+	/**
+	 * Saves the given track. This also saves all relationships of the track.
+	 *
+	 * @param track
+	 *            The track to save
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public void saveTrack(Track track) throws DatabaseException {
+		Query query = new Query(Type.UPDATE, "TRACKS");
+		query.addValueField(new ValueField("TRACKS.NAME", new StringParameter(track.getName())));
+		query.addValueField(new ValueField("TRACKS.REMIX", new StringParameter(track.getRemix())));
+		query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACKS.ID", new StringParameter(track.getId()))));
+		database.update(query);
+		/* store artist information. */
+		track.getArtists(); /* prefetch artists. */
+		query = new Query(Type.DELETE, "TRACK_ARTISTS");
+		query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_ARTISTS.TRACK", new StringParameter(track.getId()))));
+		database.update(query);
+		for (int index = 0; index < track.getArtists().size(); ++index) {
+			query = new Query(Type.INSERT, "TRACK_ARTISTS");
+			query.addValueField(new ValueField("TRACK_ARTISTS.TRACK", new StringParameter(track.getId())));
+			query.addValueField(new ValueField("TRACK_ARTISTS.ARTIST", new StringParameter(track.getArtists().get(index).getId())));
+			query.addValueField(new ValueField("TRACK_ARTISTS.DISPLAY_ORDER", new IntegerParameter(index + 1)));
+			database.insert(query);
+		}
+
+		/* store party links. */
+		Collection<Party> parties = track.getParties(); /* prefetch parties. */
+		query = new Query(Type.DELETE, "PARTY_TRACKS");
+		query.addWhereClause(new ValueFieldWhereClause(new ValueField("PARTY_TRACKS.TRACK", new StringParameter(track.getId()))));
+		database.update(query);
+		for (Party party : parties) {
+			query = new Query(Type.INSERT, "PARTY_TRACKS");
+			query.addValueField(new ValueField("PARTY_TRACKS.TRACK", new StringParameter(track.getId())));
+			query.addValueField(new ValueField("PARTY_TRACKS.PARTY", new StringParameter(party.getId())));
+			database.insert(query);
+		}
+
+		/* store properties. */
+		saveProperties(track.getProperties(), "TRACK_PROPERTIES", "TRACK", track.getId());
+	}
+
+	/**
+	 * Returns the derivative with the given ID.
+	 *
+	 * @param id
+	 *            The ID of the derivatives to load
+	 * @return The derivative with the given ID
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public TrackDerivative getTrackDerivativeById(String id) throws DatabaseException {
+		Query query = new Query(Type.SELECT, "TRACK_DERIVATIVES");
+		query.addField(new Field("TRACK_DERIVATIVES.*"));
+		query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_DERIVATIVES.ID", new StringParameter(id))));
+		return loadTrackDerivativeProperties(database.getSingle(query, trackDerivativeCreator));
+	}
+
+	/**
+	 * Returns the derivatives for the given track.
+	 *
+	 * @param trackId
+	 *            The track ID to get the derivatives for
+	 * @return The derivatives for the given track
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public Collection<TrackDerivative> getTrackDerivativesByTrack(String trackId) throws DatabaseException {
+		Query query = new Query(Type.SELECT, "TRACK_DERIVATIVES");
+		query.addField(new Field("TRACK_DERIVATIVES.*"));
+		query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_DERIVATIVES.TRACK", new StringParameter(trackId))));
+		return loadTrackDerivativeProperties(database.getMultiple(query, trackDerivativeCreator));
+	}
+
+	/**
+	 * Creates a new derivative for the given track.
+	 *
+	 * @param track
+	 *            The track to create the derivative for
+	 * @return The created derivative
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public TrackDerivative createTrackDerivative(Track track) throws DatabaseException {
+		Query query = new Query(Type.INSERT, "TRACK_DERIVATIVES");
+		String id = UUID.randomUUID().toString();
+		query.addValueField(new ValueField("TRACK_DERIVATIVES.ID", new StringParameter(id)));
+		query.addValueField(new ValueField("TRACK_DERIVATIVES.TRACK", new StringParameter(track.getId())));
+		database.insert(query);
+		return getTrackDerivativeById(id);
+	}
+
+	/**
+	 * Loads the properties for the given track derivative.
+	 *
+	 * @param trackDerivative
+	 *            The track derivative to load the properties for
+	 * @return The track derivative with its properties loaded
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public TrackDerivative loadTrackDerivativeProperties(TrackDerivative trackDerivative) throws DatabaseException {
+		return loadProperties(trackDerivative, "TRACK_DERIVATIVE_PROPERTIES", "TRACK_DERIVATIVE");
+	}
+
+	/**
+	 * Loads the properties for the given track derivatives.
+	 *
+	 * @param trackDerivatives
+	 *            The track derivatives to load the properties for
+	 * @return The track derivatives with their properties loaded
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public List<TrackDerivative> loadTrackDerivativeProperties(List<TrackDerivative> trackDerivatives) throws DatabaseException {
+		for (TrackDerivative trackDerivative : trackDerivatives) {
+			loadTrackDerivativeProperties(trackDerivative);
+		}
+		return trackDerivatives;
+	}
+
+	/**
+	 * Saves the given track derivative. As a track derivative does not have any
+	 * attributes of its own only its properties are saved.
+	 *
+	 * @param trackDerivative
+	 *            The track derivative to save
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public void saveTrackDerivate(TrackDerivative trackDerivative) throws DatabaseException {
+		saveProperties(trackDerivative.getProperties(), "TRACK_DERIVATIVE_PROPERTIES", "TRACK_DERIVATIVE", trackDerivative.getId());
+	}
+
+	/**
+	 * Removes the given track derivative and all its properties from the
+	 * database.
+	 *
+	 * @param trackDerivative
+	 *            The track derivative to remove
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public void removeTrackDerivative(TrackDerivative trackDerivative) throws DatabaseException {
+		Query query = new Query(Type.DELETE, "TRACK_DERIVATIVES");
+		query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_DERIVATIVES.ID", new StringParameter(trackDerivative.getId()))));
+		database.update(query);
+		/* remove the properties. */
+		saveProperties(new Properties().set("dirty", "true").removeAll(), "TRACK_DERIVATIVE_PROPERTIES", "TRACK_DERIVATIVE", trackDerivative.getId());
 	}
 
 	/**
@@ -394,6 +618,127 @@ public class DataManager {
 	}
 
 	/**
+	 * Returns all parties.
+	 *
+	 * @return All parties
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public Collection<Party> getAllParties() throws DatabaseException {
+		Query query = new Query(Type.SELECT, "PARTIES");
+		query.addField(new Field("PARTIES.*"));
+		return loadPartyProperties(database.getMultiple(query, partyCreator));
+	}
+
+	/**
+	 * Returns all parties that the track with the given ID was released at.
+	 *
+	 * @param trackId
+	 *            The ID of the track
+	 * @return All parties the track was released at
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public Collection<Party> getPartiesByTrackId(String trackId) throws DatabaseException {
+		Query query = new Query(Type.SELECT, "PARTIES");
+		query.addField(new Field("PARTIES.*"));
+		query.addJoin(new Join(JoinType.INNER, "PARTY_TRACKS", new Field("PARTY_TRACKS.PARTY"), new Field("PARTIES.ID")));
+		query.addWhereClause(new ValueFieldWhereClause(new ValueField("PARTY_TRACKS.TRACK", new StringParameter(trackId))));
+		return loadPartyProperties(database.getMultiple(query, partyCreator));
+	}
+
+	/**
+	 * Returns the party with the given ID.
+	 *
+	 * @param partyId
+	 *            The ID of the party
+	 * @return The party with the given ID
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public Party getPartyById(String partyId) throws DatabaseException {
+		Query query = new Query(Type.SELECT, "PARTIES");
+		query.addField(new Field("PARTIES.*"));
+		query.addWhereClause(new ValueFieldWhereClause(new ValueField("PARTIES.ID", new StringParameter(partyId))));
+		return loadPartyProperties(database.getSingle(query, partyCreator));
+	}
+
+	/**
+	 * Loads the properties of the given party.
+	 *
+	 * @param party
+	 *            The party to load the properties for
+	 * @return The party with its properties loaded
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public Party loadPartyProperties(Party party) throws DatabaseException {
+		return loadProperties(party, "PARTY_PROPERTIES", "PARTY");
+	}
+
+	/**
+	 * Loads the properties of the given parties.
+	 *
+	 * @param parties
+	 *            The parties to load the properties for
+	 * @return The parties with their properties loaded
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public List<Party> loadPartyProperties(List<Party> parties) throws DatabaseException {
+		for (Party party : parties) {
+			loadPartyProperties(party);
+		}
+		return parties;
+	}
+
+	/**
+	 * Saves the given party.
+	 *
+	 * @param party
+	 *            The party to save
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public void saveParty(Party party) throws DatabaseException {
+		Query query = new Query(Type.UPDATE, "PARTIES");
+		query.addValueField(new ValueField("NAME", new StringParameter(party.getName())));
+		query.addWhereClause(new ValueFieldWhereClause(new ValueField("ID", new StringParameter(party.getId()))));
+		database.update(query);
+		savePartyProperties(party);
+	}
+
+	/**
+	 * Saves the properties of the given party.
+	 *
+	 * @param party
+	 *            The party whose properties to save
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public void savePartyProperties(Party party) throws DatabaseException {
+		saveProperties(party.getProperties(), "PARTY_PROPERTIES", "PARTY", party.getId());
+	}
+
+	/**
+	 * Creates a new party with the given name.
+	 *
+	 * @param name
+	 *            The name of the party
+	 * @return The new party
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	public Party createParty(String name) throws DatabaseException {
+		Query query = new Query(Type.INSERT, "PARTIES");
+		String id = UUID.randomUUID().toString();
+		query.addValueField(new ValueField("ID", new StringParameter(id)));
+		query.addValueField(new ValueField("NAME", new StringParameter(name)));
+		database.insert(query);
+		return getPartyById(id);
+	}
+
+	/**
 	 * Returns the user with the given name.
 	 *
 	 * @param username
@@ -443,6 +788,47 @@ public class DataManager {
 		return database.getMultiple(query, new StringCreator("USER_OPENIDS.OPENID"));
 	}
 
+	//
+	// PRIVATE METHODS
+	//
+
+	/**
+	 * Loads the properties for the given object.
+	 *
+	 * @param <T>
+	 *            The type of the object
+	 * @param object
+	 *            The object
+	 * @param table
+	 *            The table to load the properties from
+	 * @param type
+	 *            The type of the object (“ARTIST,” “TRACK,” etc.)
+	 * @return The object with its properties loaded
+	 * @throws DatabaseException
+	 *             if a database error occurs
+	 */
+	private <T extends Base> T loadProperties(final T object, final String table, String type) throws DatabaseException {
+		if (object == null) {
+			return null;
+		}
+		Query query = new Query(Type.SELECT, table);
+		query.addField(new Field(table + ".PROPERTY"));
+		query.addField(new Field(table + ".VALUE"));
+		query.addWhereClause(new ValueFieldWhereClause(new ValueField(type, new StringParameter(object.getId()))));
+		database.process(query, new ResultProcessor() {
+
+			@Override
+			public void processResult(ResultSet resultSet) throws SQLException {
+				if (resultSet.isFirst()) {
+					object.getProperties().removeAll();
+				}
+				object.getProperties().set(resultSet.getString(table + ".PROPERTY"), resultSet.getString(table + ".VALUE"));
+			}
+
+		});
+		return object;
+	}
+
 	/**
 	 * {@link Artist} implementation that retrieves some attributes (such as
 	 * {@link #getGroups()}, and {@link #getTracks()}) from the
@@ -454,6 +840,7 @@ public class DataManager {
 
 		/** Memoizer for the tracks by this artist. */
 		private final Memoizer<Void> tracksMemoizer = new Memoizer<Void>(new Callable<Void>() {
+
 			@Override
 			public Void call() throws DatabaseException {
 				if (!hasValue("tracks")) {
@@ -642,6 +1029,19 @@ public class DataManager {
 
 		});
 
+		/** Memoizer for the track derivatives. */
+		private final Memoizer<Void> derivativesMemoizer = new Memoizer<Void>(new Callable<Void>() {
+
+			@Override
+			public Void call() throws Exception {
+				if (!hasValue("derivatives")) {
+					getValue("derivatives", Collection.class).set(getTrackDerivativesByTrack(getId()));
+				}
+				return null;
+			}
+
+		});
+
 		/** Memoizer for the related tracks. */
 		private final Memoizer<Void> relatedTracksMemoizer = new Memoizer<Void>(new Callable<Void>() {
 
@@ -652,6 +1052,7 @@ public class DataManager {
 				}
 				return null;
 			}
+
 		});
 
 		/**
@@ -699,11 +1100,35 @@ public class DataManager {
 		 * {@inheritDoc}
 		 */
 		@Override
+		public Collection<TrackDerivative> getDerivatives() {
+			derivativesMemoizer.get();
+			return super.getDerivatives();
+		}
+
+		/**
+		 * {@inheritDoc}
+		 */
+		@Override
 		public Map<Relationship, Collection<Track>> getRelatedTracks() {
 			relatedTracksMemoizer.get();
 			return super.getRelatedTracks();
 		}
 
+		/**
+		 * {@inheritDoc}
+		 */
+		@Override
+		public Collection<Party> getParties() {
+			if (!hasValue("parties")) {
+				try {
+					getValue("parties", Collection.class).set(getPartiesByTrackId(getId()));
+				} catch (DatabaseException de1) {
+					throw new RuntimeException("Could not load Parties for Track " + getId() + ".", de1);
+				}
+			}
+			return super.getParties();
+		}
+
 	}
 
 	/**
@@ -762,6 +1187,63 @@ public class DataManager {
 	}
 
 	/**
+	 * {@link Party} implementation that loads additional information only on
+	 * demand.
+	 *
+	 * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
+	 */
+	private class LazyParty extends DefaultParty {
+
+		/**
+		 * Creates a new party.
+		 *
+		 * @param id
+		 *            The ID of the party
+		 */
+		public LazyParty(String id) {
+			super(id);
+		}
+
+		//
+		// PARTY METHODS
+		//
+
+		/**
+		 * {@inheritDoc}
+		 */
+		@Override
+		public Collection<Track> getReleases() {
+			if (!hasValue("releases")) {
+				try {
+					getValue("releases", Collection.class).set(getTracksByParty(getId()));
+				} catch (DatabaseException de1) {
+					throw new RuntimeException("Could not loaded Tracks for Party " + getId() + ".", de1);
+				}
+			}
+			return super.getReleases();
+		}
+
+	}
+
+	/**
+	 * {@link ObjectCreator} implementation that can create {@link Party}
+	 * objects.
+	 *
+	 * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
+	 */
+	private class PartyCreator implements ObjectCreator<Party> {
+
+		/**
+		 * {@inheritDoc}
+		 */
+		@Override
+		public Party createObject(ResultSet resultSet) throws SQLException {
+			return new LazyParty(resultSet.getString("PARTIES.ID")).setName(resultSet.getString("PARTIES.NAME"));
+		}
+
+	}
+
+	/**
 	 * {@link User} implementation that retrieves some attributes (such as
 	 * {@link #getOpenIds()}) from the {@link DataManager} on demand.
 	 *