src/main/java/net/pterodactylus/demoscenemusic/data/DataManager.java

   1 /*
   2  * DemosceneMusic - DataManager.java - Copyright © 2012 David Roden
   3  *
   4  * This program is free software: you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation, either version 3 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 package net.pterodactylus.demoscenemusic.data;
  19
  20 import java.sql.ResultSet;
  21 import java.sql.SQLException;
  22 import java.util.Collection;
  23 import java.util.EnumMap;
  24 import java.util.HashSet;
  25 import java.util.List;
  26 import java.util.Map;
  27 import java.util.Map.Entry;
  28 import java.util.UUID;
  29 import java.util.concurrent.Callable;
  30
  31 import net.pterodactylus.demoscenemusic.data.Track.Relationship;
  32 import net.pterodactylus.util.collection.Memoizer;
  33 import net.pterodactylus.util.database.Database;
  34 import net.pterodactylus.util.database.DatabaseException;
  35 import net.pterodactylus.util.database.Field;
  36 import net.pterodactylus.util.database.Join;
  37 import net.pterodactylus.util.database.Join.JoinType;
  38 import net.pterodactylus.util.database.ObjectCreator;
  39 import net.pterodactylus.util.database.ObjectCreator.StringCreator;
  40 import net.pterodactylus.util.database.OrderField;
  41 import net.pterodactylus.util.database.Parameter.StringParameter;
  42 import net.pterodactylus.util.database.Query;
  43 import net.pterodactylus.util.database.Query.Type;
  44 import net.pterodactylus.util.database.ResultProcessor;
  45 import net.pterodactylus.util.database.ValueField;
  46 import net.pterodactylus.util.database.ValueFieldWhereClause;
  47
  48 /**
  49  * Interface between the database and the application.
  50  *
  51  * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
  52  */
  53 public class DataManager {
  54
  55         /** The artist object creator. */
  56         @SuppressWarnings("synthetic-access")
  57         private final ObjectCreator<Artist> artistCreator = new ArtistCreator();
  58
  59         /** The group object creator. */
  60         @SuppressWarnings("synthetic-access")
  61         private final ObjectCreator<Group> groupCreator = new GroupCreator();
  62
  63         /** The track object creator. */
  64         @SuppressWarnings("synthetic-access")
  65         private final ObjectCreator<Track> trackCreator = new TrackCreator();
  66
  67         /** The style object creator. */
  68         @SuppressWarnings("synthetic-access")
  69         private final ObjectCreator<Style> styleCreator = new StyleCreator();
  70
  71         /** The {@link User} object creator. */
  72         @SuppressWarnings("synthetic-access")
  73         private final ObjectCreator<User> userCreator = new UserCreator();
  74
  75         /** The database. */
  76         private final Database database;
  77
  78         /**
  79          * Creates a new data manager.
  80          *
  81          * @param database
  82          *            The database to operate on
  83          */
  84         public DataManager(Database database) {
  85                 this.database = database;
  86         }
  87
  88         /**
  89          * Returns all artists.
  90          *
  91          * @return All artists
  92          * @throws DatabaseException
  93          *             if a database error occurs
  94          */
  95         public Collection<Artist> getAllArtists() throws DatabaseException {
  96                 Query query = new Query(Type.SELECT, "ARTISTS");
  97                 query.addField(new Field("ARTISTS.*"));
  98                 return loadProperties(database.getMultiple(query, artistCreator));
  99         }
 100
 101         /**
 102          * Returns the artist with the given ID.
 103          *
 104          * @param id
 105          *            The ID of the artist
 106          * @return The artist with the given ID, or {@code null} if there is no
 107          *         artist with the given ID
 108          * @throws DatabaseException
 109          *             if a database error occurs
 110          */
 111         public Artist getArtistById(String id) throws DatabaseException {
 112                 Query query = new Query(Type.SELECT, "ARTISTS");
 113                 query.addField(new Field("ARTISTS.*"));
 114                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("ARTISTS.ID", new StringParameter(id))));
 115                 return loadProperties(database.getSingle(query, artistCreator));
 116         }
 117
 118         /**
 119          * Returns all artists that belong to the group with the given ID.
 120          *
 121          * @param groupId
 122          *            The ID of the group
 123          * @return All artists belonging to the given group
 124          * @throws DatabaseException
 125          *             if a database error occurs
 126          */
 127         public Collection<Artist> getArtistsByGroup(String groupId) throws DatabaseException {
 128                 Query query = new Query(Type.SELECT, "ARTISTS");
 129                 query.addField(new Field("ARTISTS.*"));
 130                 query.addJoin(new Join(JoinType.INNER, "GROUP_ARTISTS", new Field("ARTISTS.ID"), new Field("GROUP_ARTISTS.ARTIST")));
 131                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("GROUP_ARTISTS.GROUP_", new StringParameter(groupId))));
 132                 return loadProperties(database.getMultiple(query, artistCreator));
 133         }
 134
 135         /**
 136          * Returns all artists involved in the track with the given ID.
 137          *
 138          * @param trackId
 139          *            The ID of the track
 140          * @return All artists involved in the track, in preferred order
 141          * @throws DatabaseException
 142          *             if a database error occurs
 143          */
 144         public List<Artist> getArtistsByTrack(String trackId) throws DatabaseException {
 145                 Query query = new Query(Type.SELECT, "ARTISTS");
 146                 query.addField(new Field("ARTISTS.*"));
 147                 query.addJoin(new Join(JoinType.INNER, "TRACK_ARTISTS", new Field("TRACK_ARTISTS.ARTIST"), new Field("ARTISTS.ID")));
 148                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_ARTISTS.TRACK", new StringParameter(trackId))));
 149                 query.addOrderField(new OrderField(new Field("TRACK_ARTISTS.DISPLAY_ORDER")));
 150                 return loadProperties(database.getMultiple(query, artistCreator));
 151         }
 152
 153         /**
 154          * Creates a new artist with the given name.
 155          *
 156          * @param name
 157          *            The name of the artist
 158          * @return The created artist
 159          * @throws DatabaseException
 160          *             if a database error occurs
 161          */
 162         public Artist createArtist(String name) throws DatabaseException {
 163                 Query query = new Query(Type.INSERT, "ARTISTS");
 164                 String id = UUID.randomUUID().toString();
 165                 query.addValueField(new ValueField("ID", new StringParameter(id)));
 166                 query.addValueField(new ValueField("NAME", new StringParameter(name)));
 167                 database.insert(query);
 168                 return loadProperties(getArtistById(id));
 169         }
 170
 171         /**
 172          * Saves the given artist.
 173          *
 174          * @param artist
 175          *            The artist to save
 176          * @throws DatabaseException
 177          *             if a database error occurs
 178          */
 179         public void saveArtist(Artist artist) throws DatabaseException {
 180                 Query query = new Query(Type.UPDATE, "ARTISTS");
 181                 query.addValueField(new ValueField("NAME", new StringParameter(artist.getName())));
 182                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("ID", new StringParameter(artist.getId()))));
 183                 database.update(query);
 184                 saveArtistProperties(artist);
 185         }
 186
 187         /**
 188          * Saves the properties of the given artist.
 189          *
 190          * @param artist
 191          *            The artist whose properties to save
 192          * @throws DatabaseException
 193          *             if a database error occurs
 194          */
 195         public void saveArtistProperties(Artist artist) throws DatabaseException {
 196                 saveProperties(artist.getProperties(), "ARTIST_PROPERTIES", "ARTIST", artist.getId());
 197         }
 198
 199         /**
 200          * Saves the given properties to the given table for the given principal.
 201          *
 202          * @param properties
 203          *            The properties to save
 204          * @param table
 205          *            The table in which to save the properties
 206          * @param type
 207          *            The type of the principal (e. g. “ARTIST” or “TRACK”)
 208          * @param id
 209          *            The ID of the principial
 210          * @throws DatabaseException
 211          *             if a database error occurs
 212          */
 213         public void saveProperties(Properties properties, String table, String type, String id) throws DatabaseException {
 214                 if (!properties.isDirty()) {
 215                         return;
 216                 }
 217                 Query query = new Query(Type.DELETE, table);
 218                 query.addWhereClause(new ValueFieldWhereClause(new ValueField(type, new StringParameter(id))));
 219                 database.update(query);
 220                 for (Entry<String, String> property : properties) {
 221                         Query insertQuery = new Query(Type.INSERT, table);
 222                         insertQuery.addValueField(new ValueField(type, new StringParameter(id)));
 223                         insertQuery.addValueField(new ValueField("PROPERTY", new StringParameter(property.getKey())));
 224                         insertQuery.addValueField(new ValueField("VALUE", new StringParameter(property.getValue())));
 225                         database.insert(insertQuery);
 226                 }
 227                 properties.resetDirty();
 228         }
 229
 230         /**
 231          * Loads the properties for an artist.
 232          *
 233          * @param artist
 234          *            The artist to load the properties for
 235          * @return The artist
 236          * @throws DatabaseException
 237          *             if a database error occurs
 238          */
 239         public Artist loadProperties(final Artist artist) throws DatabaseException {
 240                 Query query = new Query(Type.SELECT, "ARTIST_PROPERTIES");
 241                 query.addField(new Field("ARTIST_PROPERTIES.PROPERTY"));
 242                 query.addField(new Field("ARTIST_PROPERTIES.VALUE"));
 243                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("ARTIST", new StringParameter(artist.getId()))));
 244                 database.process(query, new ResultProcessor() {
 245
 246                         @Override
 247                         public void processResult(ResultSet resultSet) throws SQLException {
 248                                 if (resultSet.isFirst()) {
 249                                         artist.getProperties().removeAll();
 250                                 }
 251                                 artist.getProperties().set(resultSet.getString("ARTIST_PROPERTIES.PROPERTY"), resultSet.getString("ARTIST_PROPERTIES.VALUE"));
 252                         }
 253
 254                 });
 255                 return artist;
 256         }
 257
 258         /**
 259          * Loads the properties of all given artists.
 260          *
 261          * @param artists
 262          *            The artists to load the properties for
 263          * @return The list of artists
 264          * @throws DatabaseException
 265          *             if a database error occurs
 266          */
 267         public List<Artist> loadProperties(List<Artist> artists) throws DatabaseException {
 268                 for (Artist artist : artists) {
 269                         loadProperties(artist);
 270                 }
 271                 return artists;
 272         }
 273
 274         /**
 275          * Returns all remix artists involved in the track with the given ID.
 276          *
 277          * @param trackId
 278          *            The ID of the track
 279          * @return All remix artists involved in the track, in preferred order
 280          * @throws DatabaseException
 281          *             if a database error occurs
 282          */
 283         public List<Artist> getRemixArtistsByTrack(String trackId) throws DatabaseException {
 284                 Query query = new Query(Type.SELECT, "ARTISTS");
 285                 query.addField(new Field("ARTISTS.*"));
 286                 query.addJoin(new Join(JoinType.INNER, "TRACK_REMIX_ARTISTS", new Field("TRACK_REMIX_ARTISTS.ARTIST"), new Field("ARTISTS.ID")));
 287                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_REMIX_ARTISTS.TRACK", new StringParameter(trackId))));
 288                 query.addOrderField(new OrderField(new Field("TRACK_REMIX_ARTISTS.DISPLAY_ORDER")));
 289                 return database.getMultiple(query, artistCreator);
 290         }
 291
 292         /**
 293          * Returns all related tracks for the track with the given ID.
 294          *
 295          * @param trackId
 296          *            The ID of the tracks
 297          * @return A mapping from relationship to all tracks that match the relation
 298          * @throws DatabaseException
 299          *             if a database error occurs
 300          */
 301         public Map<Relationship, Collection<Track>> getRelatedTracksByTrack(String trackId) throws DatabaseException {
 302                 Query query = new Query(Type.SELECT, "TRACKS");
 303                 query.addField(new Field("TRACKS.*"));
 304                 query.addField(new Field("TRACK_RELATIONS.*"));
 305                 query.addJoin(new Join(JoinType.INNER, "TRACK_RELATIONS", new Field("TRACK_RELATIONS.TRACK"), new Field("TRACK_RELATIONS.RELATED_TRACK")));
 306                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_RELATIONS.TRACK", new StringParameter(trackId))));
 307                 final Map<Relationship, Collection<Track>> relatedTracks = new EnumMap<Relationship, Collection<Track>>(Relationship.class);
 308                 database.process(query, new ResultProcessor() {
 309
 310                         @Override
 311                         @SuppressWarnings("synthetic-access")
 312                         public void processResult(ResultSet resultSet) throws SQLException {
 313                                 Track track = trackCreator.createObject(resultSet);
 314                                 Relationship relationship = Relationship.valueOf(resultSet.getString("TRACK_RELATIONS.RELATIONSHIP"));
 315                                 if (!relatedTracks.containsKey(relationship)) {
 316                                         relatedTracks.put(relationship, new HashSet<Track>());
 317                                 }
 318                                 relatedTracks.get(relationship).add(track);
 319                         }
 320                 });
 321                 return relatedTracks;
 322         }
 323
 324         /**
 325          * Returns the track with the given ID.
 326          *
 327          * @param id
 328          *            The ID of the track
 329          * @return The track with the given ID, or {@code null} if there is no such
 330          *         track
 331          * @throws DatabaseException
 332          *             if a database error occurs
 333          */
 334         public Track getTrackById(String id) throws DatabaseException {
 335                 Query query = new Query(Type.SELECT, "TRACKS");
 336                 query.addField(new Field("TRACKS.*"));
 337                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACKS.ID", new StringParameter(id))));
 338                 return database.getSingle(query, trackCreator);
 339         }
 340
 341         /**
 342          * Returns all tracks by the artist with the given ID.
 343          *
 344          * @param artistId
 345          *            The ID of the artist
 346          * @return All tracks by the given artist
 347          * @throws DatabaseException
 348          *             if a database error occurs
 349          */
 350         public Collection<Track> getTracksByArtist(String artistId) throws DatabaseException {
 351                 Query query = new Query(Type.SELECT, "TRACKS");
 352                 query.addField(new Field("TRACKS.*"));
 353                 query.addJoin(new Join(JoinType.INNER, "TRACK_ARTISTS", new Field("TRACKS.ID"), new Field("TRACK_ARTISTS.TRACK")));
 354                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_ARTISTS.ARTIST", new StringParameter(artistId))));
 355                 return database.getMultiple(query, trackCreator);
 356         }
 357
 358         /**
 359          * Returns all groups the artist with the given ID belongs to.
 360          *
 361          * @param artistId
 362          *            The ID of the artist
 363          * @return All groups the artist belongs to
 364          * @throws DatabaseException
 365          *             if a database error occurs
 366          */
 367         public Collection<Group> getGroupsByArtist(String artistId) throws DatabaseException {
 368                 Query query = new Query(Type.SELECT, "GROUPS");
 369                 query.addField(new Field("GROUPS.*"));
 370                 query.addJoin(new Join(JoinType.INNER, "GROUP_ARTISTS", new Field("GROUPS.ID"), new Field("GROUP_ARTISTS.GROUP_")));
 371                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("GROUP_ARTISTS.ARTIST", new StringParameter(artistId))));
 372                 return database.getMultiple(query, groupCreator);
 373         }
 374
 375         /**
 376          * Returns all styles for the track with the given ID.
 377          *
 378          * @param trackId
 379          *            The ID of the track
 380          * @return All styles for the given track
 381          * @throws DatabaseException
 382          *             if a database error occurs
 383          */
 384         public Collection<Style> getStylesByTrack(String trackId) throws DatabaseException {
 385                 Query query = new Query(Type.SELECT, "STYLES");
 386                 query.addField(new Field("STYLES.*"));
 387                 query.addJoin(new Join(JoinType.INNER, "TRACK_STYLES", new Field("STYLES.ID"), new Field("TRACK_STYLES.STYLE")));
 388                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_STYLES.TRACK", new StringParameter(trackId))));
 389                 return database.getMultiple(query, styleCreator);
 390         }
 391
 392         /**
 393          * Returns the user with the given name.
 394          *
 395          * @param username
 396          *            The name of the user
 397          * @return The user, or {@code null} if the user does not exist
 398          * @throws DatabaseException
 399          *             if a database error occurs
 400          */
 401         public User getUserByName(String username) throws DatabaseException {
 402                 Query query = new Query(Type.SELECT, "USERS");
 403                 query.addField(new Field("USERS.*"));
 404                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("USERS.NAME", new StringParameter(username))));
 405                 return database.getSingle(query, userCreator);
 406         }
 407
 408         /**
 409          * Returns the user connected with the given OpenID.
 410          *
 411          * @param openId
 412          *            The OpenID to find the user for
 413          * @return The user connected with the given OpenID, or {@code null} if
 414          *         there is no such user
 415          * @throws DatabaseException
 416          *             if a database error occurs
 417          */
 418         public User getUserByOpenId(String openId) throws DatabaseException {
 419                 Query query = new Query(Type.SELECT, "USERS");
 420                 query.addField(new Field("USERS.*"));
 421                 query.addJoin(new Join(JoinType.INNER, "USER_OPENIDS", new Field("USER_OPENIDS.USER"), new Field("USERS.ID")));
 422                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("USER_OPENIDS.OPENID", new StringParameter(openId))));
 423                 return database.getSingle(query, userCreator);
 424         }
 425
 426         /**
 427          * Returns all OpenIDs connected with the user with the given ID.
 428          *
 429          * @param userId
 430          *            The ID of the user
 431          * @return All OpenIDs connected with the given user
 432          * @throws DatabaseException
 433          *             if a database error occurs
 434          */
 435         public Collection<String> getOpenIdsByUser(String userId) throws DatabaseException {
 436                 Query query = new Query(Type.SELECT, "USER_OPENIDS");
 437                 query.addField(new Field("USER_OPENIDS.*"));
 438                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("USER_OPENIDS.USER", new StringParameter(userId))));
 439                 return database.getMultiple(query, new StringCreator("USER_OPENIDS.OPENID"));
 440         }
 441
 442         /**
 443          * {@link Artist} implementation that retrieves some attributes (such as
 444          * {@link #getGroups()}, and {@link #getTracks()}) from the
 445          * {@link DataManager} on demand.
 446          *
 447          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
 448          */
 449         private class LazyArtist extends DefaultArtist {
 450
 451                 /** Memoizer for the tracks by this artist. */
 452                 private final Memoizer<Void> tracksMemoizer = new Memoizer<Void>(new Callable<Void>() {
 453                         @Override
 454                         public Void call() throws DatabaseException {
 455                                 if (!hasValue("tracks")) {
 456                                         getValue("tracks", Collection.class).set(getTracksByArtist(getId()));
 457                                 }
 458                                 return null;
 459                         }
 460                 });
 461
 462                 /** Memoizer for the groups of this artist. */
 463                 private final Memoizer<Void> groupsMemoizer = new Memoizer<Void>(new Callable<Void>() {
 464
 465                         @Override
 466                         public Void call() throws Exception {
 467                                 if (!hasValue("groups")) {
 468                                         getValue("groups", Collection.class).set(getGroupsByArtist(getId()));
 469                                 }
 470                                 return null;
 471                         }
 472
 473                 });
 474
 475                 /**
 476                  * Creates a new lazy artist.
 477                  *
 478                  * @param id
 479                  *            The ID of the artist
 480                  */
 481                 public LazyArtist(String id) {
 482                         super(id);
 483                 }
 484
 485                 //
 486                 // DEFAULTARTIST METHODS
 487                 //
 488
 489                 /**
 490                  * {@inheritDoc}
 491                  */
 492                 @Override
 493                 public Collection<Group> getGroups() {
 494                         groupsMemoizer.get();
 495                         return super.getGroups();
 496                 }
 497
 498                 /**
 499                  * {@inheritDoc}
 500                  */
 501                 @Override
 502                 public Collection<Track> getTracks() {
 503                         tracksMemoizer.get();
 504                         return super.getTracks();
 505                 }
 506
 507         }
 508
 509         /**
 510          * {@link ObjectCreator} implementation that can create {@link Artist}
 511          * objects. This specific class actually creates {@link LazyArtist}
 512          * instances.
 513          *
 514          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
 515          */
 516         private class ArtistCreator implements ObjectCreator<Artist> {
 517
 518                 /**
 519                  * {@inheritDoc}
 520                  */
 521                 @Override
 522                 public Artist createObject(ResultSet resultSet) throws SQLException {
 523                         return new LazyArtist(resultSet.getString("ARTISTS.ID")).setName(resultSet.getString("ARTISTS.NAME"));
 524                 }
 525
 526         }
 527
 528         /**
 529          * {@link Group} implementation that retrieves some attributes (such as
 530          * {@link #getArtists()}) from the {@link DataManager} on demand.
 531          *
 532          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
 533          */
 534         private class LazyGroup extends DefaultGroup {
 535
 536                 /** Memoizer for the artist. */
 537                 private final Memoizer<Void> artistsMemoizer = new Memoizer<Void>(new Callable<Void>() {
 538
 539                         @Override
 540                         public Void call() throws Exception {
 541                                 if (!hasValue("artists")) {
 542                                         getValue("artists", Collection.class).set(getArtistsByGroup(getId()));
 543                                 }
 544                                 return null;
 545                         }
 546
 547                 });
 548
 549                 /**
 550                  * Creates a new lazy group.
 551                  *
 552                  * @param id
 553                  *            The ID of the group
 554                  */
 555                 public LazyGroup(String id) {
 556                         super(id);
 557                 }
 558
 559                 //
 560                 // DEFAULTGROUP METHODS
 561                 //
 562
 563                 /**
 564                  * {@inheritDoc}
 565                  */
 566                 @Override
 567                 public Collection<Artist> getArtists() {
 568                         artistsMemoizer.get();
 569                         return super.getArtists();
 570                 }
 571
 572         }
 573
 574         /**
 575          * {@link ObjectCreator} implementation that can create {@link Group}
 576          * objects. This specific implementation creates {@link LazyGroup}
 577          * instances.
 578          *
 579          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
 580          */
 581         private class GroupCreator implements ObjectCreator<Group> {
 582
 583                 /**
 584                  * {@inheritDoc}
 585                  */
 586                 @Override
 587                 public Group createObject(ResultSet resultSet) throws SQLException {
 588                         return new LazyGroup(resultSet.getString("GROUPS.ID")).setName(resultSet.getString("GROUPS.NAME")).setUrl(resultSet.getString("GROUPS.URL"));
 589                 }
 590
 591         }
 592
 593         /**
 594          * {@link Track} implementation that retrieves some attributes (such as
 595          * {@link #getArtists()}, and {@link #getStyles()}) from the
 596          * {@link DataManager} on demand.
 597          *
 598          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
 599          */
 600         private class LazyTrack extends DefaultTrack {
 601
 602                 /** Memoizer for the artists. */
 603                 private final Memoizer<Void> artistsMemoizer = new Memoizer<Void>(new Callable<Void>() {
 604
 605                         @Override
 606                         public Void call() throws Exception {
 607                                 if (!hasValue("artists")) {
 608                                         getValue("artists", List.class).set(getArtistsByTrack(getId()));
 609                                 }
 610                                 return null;
 611                         }
 612
 613                 });
 614
 615                 /** Memoizer for the styles. */
 616                 private final Memoizer<Void> stylesMemoizer = new Memoizer<Void>(new Callable<Void>() {
 617
 618                         @Override
 619                         public Void call() throws Exception {
 620                                 if (!hasValue("styles")) {
 621                                         getValue("styles", Collection.class).set(getStylesByTrack(getId()));
 622                                 }
 623                                 return null;
 624                         }
 625
 626                 });
 627
 628                 /** Memoizer for the remix artists. */
 629                 private final Memoizer<Void> remixArtistsMemoizer = new Memoizer<Void>(new Callable<Void>() {
 630
 631                         @Override
 632                         public Void call() throws Exception {
 633                                 if (!hasValue("remixArtists")) {
 634                                         getValue("remixArtists", List.class).set(getRemixArtistsByTrack(getId()));
 635                                 }
 636                                 return null;
 637                         }
 638
 639                 });
 640
 641                 /** Memoizer for the related tracks. */
 642                 private final Memoizer<Void> relatedTracksMemoizer = new Memoizer<Void>(new Callable<Void>() {
 643
 644                         @Override
 645                         public Void call() throws Exception {
 646                                 if (!hasValue("relatedTracks")) {
 647                                         getValue("relatedTracks", Map.class).set(getRelatedTracksByTrack(getId()));
 648                                 }
 649                                 return null;
 650                         }
 651                 });
 652
 653                 /**
 654                  * Creates a new track.
 655                  *
 656                  * @param id
 657                  *            The ID of the track
 658                  */
 659                 public LazyTrack(String id) {
 660                         super(id);
 661                 }
 662
 663                 //
 664                 // DEFAULTTRACK METHODS
 665                 //
 666
 667                 /**
 668                  * {@inheritDoc}
 669                  */
 670                 @Override
 671                 public List<Artist> getArtists() {
 672                         artistsMemoizer.get();
 673                         return super.getArtists();
 674                 }
 675
 676                 /**
 677                  * {@inheritDoc}
 678                  */
 679                 @Override
 680                 public Collection<Style> getStyles() {
 681                         stylesMemoizer.get();
 682                         return super.getStyles();
 683                 }
 684
 685                 /**
 686                  * {@inheritDoc}
 687                  */
 688                 @Override
 689                 public List<Artist> getRemixArtists() {
 690                         remixArtistsMemoizer.get();
 691                         return super.getRemixArtists();
 692                 }
 693
 694                 /**
 695                  * {@inheritDoc}
 696                  */
 697                 @Override
 698                 public Map<Relationship, Collection<Track>> getRelatedTracks() {
 699                         relatedTracksMemoizer.get();
 700                         return super.getRelatedTracks();
 701                 }
 702
 703         }
 704
 705         /**
 706          * {@link ObjectCreator} implementation that can create {@link Track}
 707          * objects. This specific implementation creates {@link LazyTrack}
 708          * instances.
 709          *
 710          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
 711          */
 712         private class TrackCreator implements ObjectCreator<Track> {
 713
 714                 /**
 715                  * {@inheritDoc}
 716                  */
 717                 @Override
 718                 public Track createObject(ResultSet resultSet) throws SQLException {
 719                         return new LazyTrack(resultSet.getString("TRACKS.ID")).setName(resultSet.getString("TRACKS.NAME")).setRemix(resultSet.getString("TRACKS.REMIX"));
 720                 }
 721
 722         }
 723
 724         /**
 725          * {@link ObjectCreator} implementation that can create {@link Style}
 726          * objects.
 727          *
 728          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
 729          */
 730         private class StyleCreator implements ObjectCreator<Style> {
 731
 732                 /**
 733                  * {@inheritDoc}
 734                  */
 735                 @Override
 736                 public Style createObject(ResultSet resultSet) throws SQLException {
 737                         return new DefaultStyle(resultSet.getString("STYLES.ID")).setName(resultSet.getString("STYLES.NAME"));
 738                 }
 739
 740         }
 741
 742         /**
 743          * {@link User} implementation that retrieves some attributes (such as
 744          * {@link #getOpenIds()}) from the {@link DataManager} on demand.
 745          *
 746          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
 747          */
 748         private class LazyUser extends DefaultUser {
 749
 750                 /** Memoizer for a user’s OpenIDs. */
 751                 private final Memoizer<Void> openIdMemoizer = new Memoizer<Void>(new Callable<Void>() {
 752
 753                         @Override
 754                         public Void call() throws Exception {
 755                                 if (!hasValue("openIds")) {
 756                                         getValue("openIds", Collection.class).set(getOpenIdsByUser(getId()));
 757                                 }
 758                                 return null;
 759                         }
 760                 });
 761
 762                 /**
 763                  * Creates a new user.
 764                  *
 765                  * @param id
 766                  *            The ID of the user
 767                  */
 768                 public LazyUser(String id) {
 769                         super(id);
 770                 }
 771
 772                 /**
 773                  * {@inheritDoc}
 774                  */
 775                 @Override
 776                 public Collection<String> getOpenIds() {
 777                         openIdMemoizer.get();
 778                         return super.getOpenIds();
 779                 }
 780
 781         }
 782
 783         /**
 784          * {@link ObjectCreator} implementation that can create {@link User}
 785          * objects. This specific implementation creates {@link LazyUser} instances.
 786          *
 787          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
 788          */
 789         private class UserCreator implements ObjectCreator<User> {
 790
 791                 /**
 792                  * {@inheritDoc}
 793                  */
 794                 @Override
 795                 public User createObject(ResultSet resultSet) throws SQLException {
 796                         return new LazyUser(resultSet.getString("USERS.ID")).setName(resultSet.getString("USERS.NAME")).setPasswordHash(resultSet.getString("USERS.PASSWORD")).setLevel(resultSet.getInt("USERS.LEVEL"));
 797                 }
 798
 799         }
 800
 801 }