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.IntegerParameter;
  42 import net.pterodactylus.util.database.Parameter.StringParameter;
  43 import net.pterodactylus.util.database.Query;
  44 import net.pterodactylus.util.database.Query.Type;
  45 import net.pterodactylus.util.database.ResultProcessor;
  46 import net.pterodactylus.util.database.ValueField;
  47 import net.pterodactylus.util.database.ValueFieldWhereClause;
  48
  49 /**
  50  * Interface between the database and the application.
  51  *
  52  * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
  53  */
  54 public class DataManager {
  55
  56         /** The artist object creator. */
  57         @SuppressWarnings("synthetic-access")
  58         private final ObjectCreator<Artist> artistCreator = new ArtistCreator();
  59
  60         /** The group object creator. */
  61         @SuppressWarnings("synthetic-access")
  62         private final ObjectCreator<Group> groupCreator = new GroupCreator();
  63
  64         /** The track object creator. */
  65         @SuppressWarnings("synthetic-access")
  66         private final ObjectCreator<Track> trackCreator = new TrackCreator();
  67
  68         /** The track object creator. */
  69         @SuppressWarnings("synthetic-access")
  70         private final ObjectCreator<TrackDerivative> trackDerivativeCreator = new TrackDerivativeCreator();
  71
  72         /** The style object creator. */
  73         @SuppressWarnings("synthetic-access")
  74         private final ObjectCreator<Style> styleCreator = new StyleCreator();
  75
  76         /** The party object creator. */
  77         @SuppressWarnings("synthetic-access")
  78         private final ObjectCreator<Party> partyCreator = new PartyCreator();
  79
  80         /** The {@link User} object creator. */
  81         @SuppressWarnings("synthetic-access")
  82         private final ObjectCreator<User> userCreator = new UserCreator();
  83
  84         /** The database. */
  85         private final Database database;
  86
  87         /**
  88          * Creates a new data manager.
  89          *
  90          * @param database
  91          *            The database to operate on
  92          */
  93         public DataManager(Database database) {
  94                 this.database = database;
  95         }
  96
  97         /**
  98          * Returns all artists.
  99          *
 100          * @return All artists
 101          * @throws DatabaseException
 102          *             if a database error occurs
 103          */
 104         public Collection<Artist> getAllArtists() throws DatabaseException {
 105                 Query query = new Query(Type.SELECT, "ARTISTS");
 106                 query.addField(new Field("ARTISTS.*"));
 107                 return loadArtistProperties(database.getMultiple(query, artistCreator));
 108         }
 109
 110         /**
 111          * Returns the artist with the given ID.
 112          *
 113          * @param id
 114          *            The ID of the artist
 115          * @return The artist with the given ID, or {@code null} if there is no
 116          *         artist with the given ID
 117          * @throws DatabaseException
 118          *             if a database error occurs
 119          */
 120         public Artist getArtistById(String id) throws DatabaseException {
 121                 Query query = new Query(Type.SELECT, "ARTISTS");
 122                 query.addField(new Field("ARTISTS.*"));
 123                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("ARTISTS.ID", new StringParameter(id))));
 124                 return loadArtistProperties(database.getSingle(query, artistCreator));
 125         }
 126
 127         /**
 128          * Returns all artists that belong to the group with the given ID.
 129          *
 130          * @param groupId
 131          *            The ID of the group
 132          * @return All artists belonging to the given group
 133          * @throws DatabaseException
 134          *             if a database error occurs
 135          */
 136         public Collection<Artist> getArtistsByGroup(String groupId) throws DatabaseException {
 137                 Query query = new Query(Type.SELECT, "ARTISTS");
 138                 query.addField(new Field("ARTISTS.*"));
 139                 query.addJoin(new Join(JoinType.INNER, "GROUP_ARTISTS", new Field("ARTISTS.ID"), new Field("GROUP_ARTISTS.ARTIST")));
 140                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("GROUP_ARTISTS.GROUP_", new StringParameter(groupId))));
 141                 return loadArtistProperties(database.getMultiple(query, artistCreator));
 142         }
 143
 144         /**
 145          * Returns all artists involved in the track with the given ID.
 146          *
 147          * @param trackId
 148          *            The ID of the track
 149          * @return All artists involved in the track, in preferred order
 150          * @throws DatabaseException
 151          *             if a database error occurs
 152          */
 153         public List<Artist> getArtistsByTrack(String trackId) throws DatabaseException {
 154                 Query query = new Query(Type.SELECT, "ARTISTS");
 155                 query.addField(new Field("ARTISTS.*"));
 156                 query.addJoin(new Join(JoinType.INNER, "TRACK_ARTISTS", new Field("TRACK_ARTISTS.ARTIST"), new Field("ARTISTS.ID")));
 157                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_ARTISTS.TRACK", new StringParameter(trackId))));
 158                 query.addOrderField(new OrderField(new Field("TRACK_ARTISTS.DISPLAY_ORDER")));
 159                 return loadArtistProperties(database.getMultiple(query, artistCreator));
 160         }
 161
 162         /**
 163          * Creates a new artist with the given name.
 164          *
 165          * @param name
 166          *            The name of the artist
 167          * @return The created artist
 168          * @throws DatabaseException
 169          *             if a database error occurs
 170          */
 171         public Artist createArtist(String name) throws DatabaseException {
 172                 Query query = new Query(Type.INSERT, "ARTISTS");
 173                 String id = UUID.randomUUID().toString();
 174                 query.addValueField(new ValueField("ID", new StringParameter(id)));
 175                 query.addValueField(new ValueField("NAME", new StringParameter(name)));
 176                 database.insert(query);
 177                 return loadArtistProperties(getArtistById(id));
 178         }
 179
 180         /**
 181          * Saves the given artist.
 182          *
 183          * @param artist
 184          *            The artist to save
 185          * @throws DatabaseException
 186          *             if a database error occurs
 187          */
 188         public void saveArtist(Artist artist) throws DatabaseException {
 189                 Query query = new Query(Type.UPDATE, "ARTISTS");
 190                 query.addValueField(new ValueField("NAME", new StringParameter(artist.getName())));
 191                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("ID", new StringParameter(artist.getId()))));
 192                 database.update(query);
 193                 saveArtistProperties(artist);
 194         }
 195
 196         /**
 197          * Saves the properties of the given artist.
 198          *
 199          * @param artist
 200          *            The artist whose properties to save
 201          * @throws DatabaseException
 202          *             if a database error occurs
 203          */
 204         public void saveArtistProperties(Artist artist) throws DatabaseException {
 205                 saveProperties(artist.getProperties(), "ARTIST_PROPERTIES", "ARTIST", artist.getId());
 206         }
 207
 208         /**
 209          * Saves the given properties to the given table for the given principal.
 210          *
 211          * @param properties
 212          *            The properties to save
 213          * @param table
 214          *            The table in which to save the properties
 215          * @param type
 216          *            The type of the principal (e. g. “ARTIST” or “TRACK”)
 217          * @param id
 218          *            The ID of the principial
 219          * @throws DatabaseException
 220          *             if a database error occurs
 221          */
 222         public void saveProperties(Properties properties, String table, String type, String id) throws DatabaseException {
 223                 if (!properties.isDirty()) {
 224                         return;
 225                 }
 226                 Query query = new Query(Type.DELETE, table);
 227                 query.addWhereClause(new ValueFieldWhereClause(new ValueField(type, new StringParameter(id))));
 228                 database.update(query);
 229                 for (Entry<String, String> property : properties) {
 230                         Query insertQuery = new Query(Type.INSERT, table);
 231                         insertQuery.addValueField(new ValueField(type, new StringParameter(id)));
 232                         insertQuery.addValueField(new ValueField("PROPERTY", new StringParameter(property.getKey())));
 233                         insertQuery.addValueField(new ValueField("VALUE", new StringParameter(property.getValue())));
 234                         database.insert(insertQuery);
 235                 }
 236                 properties.resetDirty();
 237         }
 238
 239         /**
 240          * Loads the properties for an artist.
 241          *
 242          * @param artist
 243          *            The artist to load the properties for
 244          * @return The artist
 245          * @throws DatabaseException
 246          *             if a database error occurs
 247          */
 248         public Artist loadArtistProperties(final Artist artist) throws DatabaseException {
 249                 return loadProperties(artist, "ARTIST_PROPERTIES", "ARTIST");
 250         }
 251
 252         /**
 253          * Loads the properties of all given artists.
 254          *
 255          * @param artists
 256          *            The artists to load the properties for
 257          * @return The list of artists
 258          * @throws DatabaseException
 259          *             if a database error occurs
 260          */
 261         public List<Artist> loadArtistProperties(List<Artist> artists) throws DatabaseException {
 262                 for (Artist artist : artists) {
 263                         loadArtistProperties(artist);
 264                 }
 265                 return artists;
 266         }
 267
 268         /**
 269          * Returns all remix artists involved in the track with the given ID.
 270          *
 271          * @param trackId
 272          *            The ID of the track
 273          * @return All remix artists involved in the track, in preferred order
 274          * @throws DatabaseException
 275          *             if a database error occurs
 276          */
 277         public List<Artist> getRemixArtistsByTrack(String trackId) throws DatabaseException {
 278                 Query query = new Query(Type.SELECT, "ARTISTS");
 279                 query.addField(new Field("ARTISTS.*"));
 280                 query.addJoin(new Join(JoinType.INNER, "TRACK_REMIX_ARTISTS", new Field("TRACK_REMIX_ARTISTS.ARTIST"), new Field("ARTISTS.ID")));
 281                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_REMIX_ARTISTS.TRACK", new StringParameter(trackId))));
 282                 query.addOrderField(new OrderField(new Field("TRACK_REMIX_ARTISTS.DISPLAY_ORDER")));
 283                 return database.getMultiple(query, artistCreator);
 284         }
 285
 286         /**
 287          * Returns all related tracks for the track with the given ID.
 288          *
 289          * @param trackId
 290          *            The ID of the tracks
 291          * @return A mapping from relationship to all tracks that match the relation
 292          * @throws DatabaseException
 293          *             if a database error occurs
 294          */
 295         public Map<Relationship, Collection<Track>> getRelatedTracksByTrack(String trackId) throws DatabaseException {
 296                 Query query = new Query(Type.SELECT, "TRACKS");
 297                 query.addField(new Field("TRACKS.*"));
 298                 query.addField(new Field("TRACK_RELATIONS.*"));
 299                 query.addJoin(new Join(JoinType.INNER, "TRACK_RELATIONS", new Field("TRACK_RELATIONS.TRACK"), new Field("TRACK_RELATIONS.RELATED_TRACK")));
 300                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_RELATIONS.TRACK", new StringParameter(trackId))));
 301                 final Map<Relationship, Collection<Track>> relatedTracks = new EnumMap<Relationship, Collection<Track>>(Relationship.class);
 302                 database.process(query, new ResultProcessor() {
 303
 304                         @Override
 305                         @SuppressWarnings("synthetic-access")
 306                         public void processResult(ResultSet resultSet) throws SQLException {
 307                                 Track track = trackCreator.createObject(resultSet);
 308                                 Relationship relationship = Relationship.valueOf(resultSet.getString("TRACK_RELATIONS.RELATIONSHIP"));
 309                                 if (!relatedTracks.containsKey(relationship)) {
 310                                         relatedTracks.put(relationship, new HashSet<Track>());
 311                                 }
 312                                 relatedTracks.get(relationship).add(track);
 313                         }
 314                 });
 315                 return relatedTracks;
 316         }
 317
 318         /**
 319          * Returns the track with the given ID.
 320          *
 321          * @param id
 322          *            The ID of the track
 323          * @return The track with the given ID, or {@code null} if there is no such
 324          *         track
 325          * @throws DatabaseException
 326          *             if a database error occurs
 327          */
 328         public Track getTrackById(String id) throws DatabaseException {
 329                 Query query = new Query(Type.SELECT, "TRACKS");
 330                 query.addField(new Field("TRACKS.*"));
 331                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACKS.ID", new StringParameter(id))));
 332                 return loadTrackProperties(database.getSingle(query, trackCreator));
 333         }
 334
 335         /**
 336          * Returns the track that contains the derivative with the given ID.
 337          *
 338          * @param id
 339          *            The ID of the track derivative
 340          * @return The track the derivative belongs to, or {@code null} if there is
 341          *         no such track
 342          * @throws DatabaseException
 343          *             if a database error occurs
 344          */
 345         public Track getTrackByDerivativeId(String id) throws DatabaseException {
 346                 Query query = new Query(Type.SELECT, "TRACKS");
 347                 query.addField(new Field("TRACKS.*"));
 348                 query.addJoin(new Join(JoinType.INNER, "TRACK_DERIVATIVES", new Field("TRACK_DERIVATIVES.TRACK"), new Field("TRACKS.ID")));
 349                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_DERIVATIVES.ID", new StringParameter(id))));
 350                 return loadTrackProperties(database.getSingle(query, trackCreator));
 351         }
 352
 353         /**
 354          * Returns all tracks by the artist with the given ID.
 355          *
 356          * @param artistId
 357          *            The ID of the artist
 358          * @return All tracks by the given artist
 359          * @throws DatabaseException
 360          *             if a database error occurs
 361          */
 362         public Collection<Track> getTracksByArtist(String artistId) throws DatabaseException {
 363                 Query query = new Query(Type.SELECT, "TRACKS");
 364                 query.addField(new Field("TRACKS.*"));
 365                 query.addJoin(new Join(JoinType.INNER, "TRACK_ARTISTS", new Field("TRACKS.ID"), new Field("TRACK_ARTISTS.TRACK")));
 366                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_ARTISTS.ARTIST", new StringParameter(artistId))));
 367                 return loadTrackProperties(database.getMultiple(query, trackCreator));
 368         }
 369
 370         /**
 371          * Returns all tracks that were released at the party with the given ID.
 372          *
 373          * @param partyId
 374          *            The ID of the party
 375          * @return All tracks that were released at the given party
 376          * @throws DatabaseException
 377          *             if a database error occurs
 378          */
 379         public Collection<Track> getTracksByParty(String partyId) throws DatabaseException {
 380                 Query query = new Query(Type.SELECT, "TRACKS");
 381                 query.addField(new Field("TRACKS.*"));
 382                 query.addJoin(new Join(JoinType.INNER, "PARTY_TRACKS", new Field("PARTY_TRACKS.TRACK"), new Field("TRACKS.ID")));
 383                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("PARTY_TRACKS.PARTY", new StringParameter(partyId))));
 384                 return loadTrackProperties(database.getMultiple(query, trackCreator));
 385         }
 386
 387         /**
 388          * Loads the properties for the given track.
 389          *
 390          * @param track
 391          *            The track for which to load the properties
 392          * @return The track with the properties loaded
 393          * @throws DatabaseException
 394          *             if a database error occurs
 395          */
 396         public Track loadTrackProperties(Track track) throws DatabaseException {
 397                 return loadProperties(track, "TRACK_PROPERTIES", "TRACK");
 398         }
 399
 400         /**
 401          * Loads the properties for the given tracks.
 402          *
 403          * @param tracks
 404          *            The tracks for which to load the properties
 405          * @return The tracks with the properties loaded
 406          * @throws DatabaseException
 407          *             if a database error occurs
 408          */
 409         public List<Track> loadTrackProperties(List<Track> tracks) throws DatabaseException {
 410                 for (Track track : tracks) {
 411                         loadTrackProperties(track);
 412                 }
 413                 return tracks;
 414         }
 415
 416         /**
 417          * Creates a new track with the given name.
 418          *
 419          * @param name
 420          *            The name of the track
 421          * @return The created track
 422          * @throws DatabaseException
 423          *             if a database error occurs
 424          */
 425         public Track createTrack(String name) throws DatabaseException {
 426                 Query query = new Query(Type.INSERT, "TRACKS");
 427                 String id = UUID.randomUUID().toString();
 428                 query.addValueField(new ValueField("ID", new StringParameter(id)));
 429                 query.addValueField(new ValueField("NAME", new StringParameter(name)));
 430                 database.insert(query);
 431                 return getTrackById(id);
 432         }
 433
 434         /**
 435          * Saves the given track. This also saves all relationships of the track.
 436          *
 437          * @param track
 438          *            The track to save
 439          * @throws DatabaseException
 440          *             if a database error occurs
 441          */
 442         public void saveTrack(Track track) throws DatabaseException {
 443                 Query query = new Query(Type.UPDATE, "TRACKS");
 444                 query.addValueField(new ValueField("TRACKS.NAME", new StringParameter(track.getName())));
 445                 query.addValueField(new ValueField("TRACKS.REMIX", new StringParameter(track.getRemix())));
 446                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACKS.ID", new StringParameter(track.getId()))));
 447                 database.update(query);
 448                 /* store artist information. */
 449                 track.getArtists(); /* prefetch artists. */
 450                 query = new Query(Type.DELETE, "TRACK_ARTISTS");
 451                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_ARTISTS.TRACK", new StringParameter(track.getId()))));
 452                 database.update(query);
 453                 for (int index = 0; index < track.getArtists().size(); ++index) {
 454                         query = new Query(Type.INSERT, "TRACK_ARTISTS");
 455                         query.addValueField(new ValueField("TRACK_ARTISTS.TRACK", new StringParameter(track.getId())));
 456                         query.addValueField(new ValueField("TRACK_ARTISTS.ARTIST", new StringParameter(track.getArtists().get(index).getId())));
 457                         query.addValueField(new ValueField("TRACK_ARTISTS.DISPLAY_ORDER", new IntegerParameter(index + 1)));
 458                         database.insert(query);
 459                 }
 460
 461                 /* store party links. */
 462                 Collection<Party> parties = track.getParties(); /* prefetch parties. */
 463                 query = new Query(Type.DELETE, "PARTY_TRACKS");
 464                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("PARTY_TRACKS.TRACK", new StringParameter(track.getId()))));
 465                 database.update(query);
 466                 for (Party party : parties) {
 467                         query = new Query(Type.INSERT, "PARTY_TRACKS");
 468                         query.addValueField(new ValueField("PARTY_TRACKS.TRACK", new StringParameter(track.getId())));
 469                         query.addValueField(new ValueField("PARTY_TRACKS.PARTY", new StringParameter(party.getId())));
 470                         database.insert(query);
 471                 }
 472
 473                 /* store properties. */
 474                 saveProperties(track.getProperties(), "TRACK_PROPERTIES", "TRACK", track.getId());
 475         }
 476
 477         /**
 478          * Returns the derivative with the given ID.
 479          *
 480          * @param id
 481          *            The ID of the derivatives to load
 482          * @return The derivative with the given ID
 483          * @throws DatabaseException
 484          *             if a database error occurs
 485          */
 486         public TrackDerivative getTrackDerivativeById(String id) throws DatabaseException {
 487                 Query query = new Query(Type.SELECT, "TRACK_DERIVATIVES");
 488                 query.addField(new Field("TRACK_DERIVATIVES.*"));
 489                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_DERIVATIVES.ID", new StringParameter(id))));
 490                 return loadTrackDerivativeProperties(database.getSingle(query, trackDerivativeCreator));
 491         }
 492
 493         /**
 494          * Returns the derivatives for the given track.
 495          *
 496          * @param trackId
 497          *            The track ID to get the derivatives for
 498          * @return The derivatives for the given track
 499          * @throws DatabaseException
 500          *             if a database error occurs
 501          */
 502         public Collection<TrackDerivative> getTrackDerivativesByTrack(String trackId) throws DatabaseException {
 503                 Query query = new Query(Type.SELECT, "TRACK_DERIVATIVES");
 504                 query.addField(new Field("TRACK_DERIVATIVES.*"));
 505                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_DERIVATIVES.TRACK", new StringParameter(trackId))));
 506                 return loadTrackDerivativeProperties(database.getMultiple(query, trackDerivativeCreator));
 507         }
 508
 509         /**
 510          * Creates a new derivative for the given track.
 511          *
 512          * @param track
 513          *            The track to create the derivative for
 514          * @return The created derivative
 515          * @throws DatabaseException
 516          *             if a database error occurs
 517          */
 518         public TrackDerivative createTrackDerivative(Track track) throws DatabaseException {
 519                 Query query = new Query(Type.INSERT, "TRACK_DERIVATIVES");
 520                 String id = UUID.randomUUID().toString();
 521                 query.addValueField(new ValueField("TRACK_DERIVATIVES.ID", new StringParameter(id)));
 522                 query.addValueField(new ValueField("TRACK_DERIVATIVES.TRACK", new StringParameter(track.getId())));
 523                 database.insert(query);
 524                 return getTrackDerivativeById(id);
 525         }
 526
 527         /**
 528          * Loads the properties for the given track derivative.
 529          *
 530          * @param trackDerivative
 531          *            The track derivative to load the properties for
 532          * @return The track derivative with its properties loaded
 533          * @throws DatabaseException
 534          *             if a database error occurs
 535          */
 536         public TrackDerivative loadTrackDerivativeProperties(TrackDerivative trackDerivative) throws DatabaseException {
 537                 return loadProperties(trackDerivative, "TRACK_DERIVATIVE_PROPERTIES", "TRACK_DERIVATIVE");
 538         }
 539
 540         /**
 541          * Loads the properties for the given track derivatives.
 542          *
 543          * @param trackDerivatives
 544          *            The track derivatives to load the properties for
 545          * @return The track derivatives with their properties loaded
 546          * @throws DatabaseException
 547          *             if a database error occurs
 548          */
 549         public List<TrackDerivative> loadTrackDerivativeProperties(List<TrackDerivative> trackDerivatives) throws DatabaseException {
 550                 for (TrackDerivative trackDerivative : trackDerivatives) {
 551                         loadTrackDerivativeProperties(trackDerivative);
 552                 }
 553                 return trackDerivatives;
 554         }
 555
 556         /**
 557          * Saves the given track derivative. As a track derivative does not have any
 558          * attributes of its own only its properties are saved.
 559          *
 560          * @param trackDerivative
 561          *            The track derivative to save
 562          * @throws DatabaseException
 563          *             if a database error occurs
 564          */
 565         public void saveTrackDerivate(TrackDerivative trackDerivative) throws DatabaseException {
 566                 saveProperties(trackDerivative.getProperties(), "TRACK_DERIVATIVE_PROPERTIES", "TRACK_DERIVATIVE", trackDerivative.getId());
 567         }
 568
 569         /**
 570          * Removes the given track derivative and all its properties from the
 571          * database.
 572          *
 573          * @param trackDerivative
 574          *            The track derivative to remove
 575          * @throws DatabaseException
 576          *             if a database error occurs
 577          */
 578         public void removeTrackDerivative(TrackDerivative trackDerivative) throws DatabaseException {
 579                 Query query = new Query(Type.DELETE, "TRACK_DERIVATIVES");
 580                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_DERIVATIVES.ID", new StringParameter(trackDerivative.getId()))));
 581                 database.update(query);
 582                 /* remove the properties. */
 583                 saveProperties(new Properties().set("dirty", "true").removeAll(), "TRACK_DERIVATIVE_PROPERTIES", "TRACK_DERIVATIVE", trackDerivative.getId());
 584         }
 585
 586         /**
 587          * Returns all groups the artist with the given ID belongs to.
 588          *
 589          * @param artistId
 590          *            The ID of the artist
 591          * @return All groups the artist belongs to
 592          * @throws DatabaseException
 593          *             if a database error occurs
 594          */
 595         public Collection<Group> getGroupsByArtist(String artistId) throws DatabaseException {
 596                 Query query = new Query(Type.SELECT, "GROUPS");
 597                 query.addField(new Field("GROUPS.*"));
 598                 query.addJoin(new Join(JoinType.INNER, "GROUP_ARTISTS", new Field("GROUPS.ID"), new Field("GROUP_ARTISTS.GROUP_")));
 599                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("GROUP_ARTISTS.ARTIST", new StringParameter(artistId))));
 600                 return database.getMultiple(query, groupCreator);
 601         }
 602
 603         /**
 604          * Returns all styles for the track with the given ID.
 605          *
 606          * @param trackId
 607          *            The ID of the track
 608          * @return All styles for the given track
 609          * @throws DatabaseException
 610          *             if a database error occurs
 611          */
 612         public Collection<Style> getStylesByTrack(String trackId) throws DatabaseException {
 613                 Query query = new Query(Type.SELECT, "STYLES");
 614                 query.addField(new Field("STYLES.*"));
 615                 query.addJoin(new Join(JoinType.INNER, "TRACK_STYLES", new Field("STYLES.ID"), new Field("TRACK_STYLES.STYLE")));
 616                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("TRACK_STYLES.TRACK", new StringParameter(trackId))));
 617                 return database.getMultiple(query, styleCreator);
 618         }
 619
 620         /**
 621          * Returns all parties.
 622          *
 623          * @return All parties
 624          * @throws DatabaseException
 625          *             if a database error occurs
 626          */
 627         public Collection<Party> getAllParties() throws DatabaseException {
 628                 Query query = new Query(Type.SELECT, "PARTIES");
 629                 query.addField(new Field("PARTIES.*"));
 630                 return loadPartyProperties(database.getMultiple(query, partyCreator));
 631         }
 632
 633         /**
 634          * Returns all parties that the track with the given ID was released at.
 635          *
 636          * @param trackId
 637          *            The ID of the track
 638          * @return All parties the track was released at
 639          * @throws DatabaseException
 640          *             if a database error occurs
 641          */
 642         public Collection<Party> getPartiesByTrackId(String trackId) throws DatabaseException {
 643                 Query query = new Query(Type.SELECT, "PARTIES");
 644                 query.addField(new Field("PARTIES.*"));
 645                 query.addJoin(new Join(JoinType.INNER, "PARTY_TRACKS", new Field("PARTY_TRACKS.PARTY"), new Field("PARTIES.ID")));
 646                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("PARTY_TRACKS.TRACK", new StringParameter(trackId))));
 647                 return loadPartyProperties(database.getMultiple(query, partyCreator));
 648         }
 649
 650         /**
 651          * Returns the party with the given ID.
 652          *
 653          * @param partyId
 654          *            The ID of the party
 655          * @return The party with the given ID
 656          * @throws DatabaseException
 657          *             if a database error occurs
 658          */
 659         public Party getPartyById(String partyId) throws DatabaseException {
 660                 Query query = new Query(Type.SELECT, "PARTIES");
 661                 query.addField(new Field("PARTIES.*"));
 662                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("PARTIES.ID", new StringParameter(partyId))));
 663                 return loadPartyProperties(database.getSingle(query, partyCreator));
 664         }
 665
 666         /**
 667          * Loads the properties of the given party.
 668          *
 669          * @param party
 670          *            The party to load the properties for
 671          * @return The party with its properties loaded
 672          * @throws DatabaseException
 673          *             if a database error occurs
 674          */
 675         public Party loadPartyProperties(Party party) throws DatabaseException {
 676                 return loadProperties(party, "PARTY_PROPERTIES", "PARTY");
 677         }
 678
 679         /**
 680          * Loads the properties of the given parties.
 681          *
 682          * @param parties
 683          *            The parties to load the properties for
 684          * @return The parties with their properties loaded
 685          * @throws DatabaseException
 686          *             if a database error occurs
 687          */
 688         public List<Party> loadPartyProperties(List<Party> parties) throws DatabaseException {
 689                 for (Party party : parties) {
 690                         loadPartyProperties(party);
 691                 }
 692                 return parties;
 693         }
 694
 695         /**
 696          * Saves the given party.
 697          *
 698          * @param party
 699          *            The party to save
 700          * @throws DatabaseException
 701          *             if a database error occurs
 702          */
 703         public void saveParty(Party party) throws DatabaseException {
 704                 Query query = new Query(Type.UPDATE, "PARTIES");
 705                 query.addValueField(new ValueField("NAME", new StringParameter(party.getName())));
 706                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("ID", new StringParameter(party.getId()))));
 707                 database.update(query);
 708                 savePartyProperties(party);
 709         }
 710
 711         /**
 712          * Saves the properties of the given party.
 713          *
 714          * @param party
 715          *            The party whose properties to save
 716          * @throws DatabaseException
 717          *             if a database error occurs
 718          */
 719         public void savePartyProperties(Party party) throws DatabaseException {
 720                 saveProperties(party.getProperties(), "PARTY_PROPERTIES", "PARTY", party.getId());
 721         }
 722
 723         /**
 724          * Creates a new party with the given name.
 725          *
 726          * @param name
 727          *            The name of the party
 728          * @return The new party
 729          * @throws DatabaseException
 730          *             if a database error occurs
 731          */
 732         public Party createParty(String name) throws DatabaseException {
 733                 Query query = new Query(Type.INSERT, "PARTIES");
 734                 String id = UUID.randomUUID().toString();
 735                 query.addValueField(new ValueField("ID", new StringParameter(id)));
 736                 query.addValueField(new ValueField("NAME", new StringParameter(name)));
 737                 database.insert(query);
 738                 return getPartyById(id);
 739         }
 740
 741         /**
 742          * Returns the user with the given name.
 743          *
 744          * @param username
 745          *            The name of the user
 746          * @return The user, or {@code null} if the user does not exist
 747          * @throws DatabaseException
 748          *             if a database error occurs
 749          */
 750         public User getUserByName(String username) throws DatabaseException {
 751                 Query query = new Query(Type.SELECT, "USERS");
 752                 query.addField(new Field("USERS.*"));
 753                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("USERS.NAME", new StringParameter(username))));
 754                 return database.getSingle(query, userCreator);
 755         }
 756
 757         /**
 758          * Returns the user connected with the given OpenID.
 759          *
 760          * @param openId
 761          *            The OpenID to find the user for
 762          * @return The user connected with the given OpenID, or {@code null} if
 763          *         there is no such user
 764          * @throws DatabaseException
 765          *             if a database error occurs
 766          */
 767         public User getUserByOpenId(String openId) throws DatabaseException {
 768                 Query query = new Query(Type.SELECT, "USERS");
 769                 query.addField(new Field("USERS.*"));
 770                 query.addJoin(new Join(JoinType.INNER, "USER_OPENIDS", new Field("USER_OPENIDS.USER"), new Field("USERS.ID")));
 771                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("USER_OPENIDS.OPENID", new StringParameter(openId))));
 772                 return database.getSingle(query, userCreator);
 773         }
 774
 775         /**
 776          * Returns all OpenIDs connected with the user with the given ID.
 777          *
 778          * @param userId
 779          *            The ID of the user
 780          * @return All OpenIDs connected with the given user
 781          * @throws DatabaseException
 782          *             if a database error occurs
 783          */
 784         public Collection<String> getOpenIdsByUser(String userId) throws DatabaseException {
 785                 Query query = new Query(Type.SELECT, "USER_OPENIDS");
 786                 query.addField(new Field("USER_OPENIDS.*"));
 787                 query.addWhereClause(new ValueFieldWhereClause(new ValueField("USER_OPENIDS.USER", new StringParameter(userId))));
 788                 return database.getMultiple(query, new StringCreator("USER_OPENIDS.OPENID"));
 789         }
 790
 791         //
 792         // PRIVATE METHODS
 793         //
 794
 795         /**
 796          * Loads the properties for the given object.
 797          *
 798          * @param <T>
 799          *            The type of the object
 800          * @param object
 801          *            The object
 802          * @param table
 803          *            The table to load the properties from
 804          * @param type
 805          *            The type of the object (“ARTIST,” “TRACK,” etc.)
 806          * @return The object with its properties loaded
 807          * @throws DatabaseException
 808          *             if a database error occurs
 809          */
 810         private <T extends Base> T loadProperties(final T object, final String table, String type) throws DatabaseException {
 811                 Query query = new Query(Type.SELECT, table);
 812                 query.addField(new Field(table + ".PROPERTY"));
 813                 query.addField(new Field(table + ".VALUE"));
 814                 query.addWhereClause(new ValueFieldWhereClause(new ValueField(type, new StringParameter(object.getId()))));
 815                 database.process(query, new ResultProcessor() {
 816
 817                         @Override
 818                         public void processResult(ResultSet resultSet) throws SQLException {
 819                                 if (resultSet.isFirst()) {
 820                                         object.getProperties().removeAll();
 821                                 }
 822                                 object.getProperties().set(resultSet.getString(table + ".PROPERTY"), resultSet.getString(table + ".VALUE"));
 823                         }
 824
 825                 });
 826                 return object;
 827         }
 828
 829         /**
 830          * {@link Artist} implementation that retrieves some attributes (such as
 831          * {@link #getGroups()}, and {@link #getTracks()}) from the
 832          * {@link DataManager} on demand.
 833          *
 834          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
 835          */
 836         private class LazyArtist extends DefaultArtist {
 837
 838                 /** Memoizer for the tracks by this artist. */
 839                 private final Memoizer<Void> tracksMemoizer = new Memoizer<Void>(new Callable<Void>() {
 840
 841                         @Override
 842                         public Void call() throws DatabaseException {
 843                                 if (!hasValue("tracks")) {
 844                                         getValue("tracks", Collection.class).set(getTracksByArtist(getId()));
 845                                 }
 846                                 return null;
 847                         }
 848                 });
 849
 850                 /** Memoizer for the groups of this artist. */
 851                 private final Memoizer<Void> groupsMemoizer = new Memoizer<Void>(new Callable<Void>() {
 852
 853                         @Override
 854                         public Void call() throws Exception {
 855                                 if (!hasValue("groups")) {
 856                                         getValue("groups", Collection.class).set(getGroupsByArtist(getId()));
 857                                 }
 858                                 return null;
 859                         }
 860
 861                 });
 862
 863                 /**
 864                  * Creates a new lazy artist.
 865                  *
 866                  * @param id
 867                  *            The ID of the artist
 868                  */
 869                 public LazyArtist(String id) {
 870                         super(id);
 871                 }
 872
 873                 //
 874                 // DEFAULTARTIST METHODS
 875                 //
 876
 877                 /**
 878                  * {@inheritDoc}
 879                  */
 880                 @Override
 881                 public Collection<Group> getGroups() {
 882                         groupsMemoizer.get();
 883                         return super.getGroups();
 884                 }
 885
 886                 /**
 887                  * {@inheritDoc}
 888                  */
 889                 @Override
 890                 public Collection<Track> getTracks() {
 891                         tracksMemoizer.get();
 892                         return super.getTracks();
 893                 }
 894
 895         }
 896
 897         /**
 898          * {@link ObjectCreator} implementation that can create {@link Artist}
 899          * objects. This specific class actually creates {@link LazyArtist}
 900          * instances.
 901          *
 902          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
 903          */
 904         private class ArtistCreator implements ObjectCreator<Artist> {
 905
 906                 /**
 907                  * {@inheritDoc}
 908                  */
 909                 @Override
 910                 public Artist createObject(ResultSet resultSet) throws SQLException {
 911                         return new LazyArtist(resultSet.getString("ARTISTS.ID")).setName(resultSet.getString("ARTISTS.NAME"));
 912                 }
 913
 914         }
 915
 916         /**
 917          * {@link Group} implementation that retrieves some attributes (such as
 918          * {@link #getArtists()}) from the {@link DataManager} on demand.
 919          *
 920          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
 921          */
 922         private class LazyGroup extends DefaultGroup {
 923
 924                 /** Memoizer for the artist. */
 925                 private final Memoizer<Void> artistsMemoizer = new Memoizer<Void>(new Callable<Void>() {
 926
 927                         @Override
 928                         public Void call() throws Exception {
 929                                 if (!hasValue("artists")) {
 930                                         getValue("artists", Collection.class).set(getArtistsByGroup(getId()));
 931                                 }
 932                                 return null;
 933                         }
 934
 935                 });
 936
 937                 /**
 938                  * Creates a new lazy group.
 939                  *
 940                  * @param id
 941                  *            The ID of the group
 942                  */
 943                 public LazyGroup(String id) {
 944                         super(id);
 945                 }
 946
 947                 //
 948                 // DEFAULTGROUP METHODS
 949                 //
 950
 951                 /**
 952                  * {@inheritDoc}
 953                  */
 954                 @Override
 955                 public Collection<Artist> getArtists() {
 956                         artistsMemoizer.get();
 957                         return super.getArtists();
 958                 }
 959
 960         }
 961
 962         /**
 963          * {@link ObjectCreator} implementation that can create {@link Group}
 964          * objects. This specific implementation creates {@link LazyGroup}
 965          * instances.
 966          *
 967          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
 968          */
 969         private class GroupCreator implements ObjectCreator<Group> {
 970
 971                 /**
 972                  * {@inheritDoc}
 973                  */
 974                 @Override
 975                 public Group createObject(ResultSet resultSet) throws SQLException {
 976                         return new LazyGroup(resultSet.getString("GROUPS.ID")).setName(resultSet.getString("GROUPS.NAME")).setUrl(resultSet.getString("GROUPS.URL"));
 977                 }
 978
 979         }
 980
 981         /**
 982          * {@link Track} implementation that retrieves some attributes (such as
 983          * {@link #getArtists()}, and {@link #getStyles()}) from the
 984          * {@link DataManager} on demand.
 985          *
 986          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
 987          */
 988         private class LazyTrack extends DefaultTrack {
 989
 990                 /** Memoizer for the artists. */
 991                 private final Memoizer<Void> artistsMemoizer = new Memoizer<Void>(new Callable<Void>() {
 992
 993                         @Override
 994                         public Void call() throws Exception {
 995                                 if (!hasValue("artists")) {
 996                                         getValue("artists", List.class).set(getArtistsByTrack(getId()));
 997                                 }
 998                                 return null;
 999                         }
1000
1001                 });
1002
1003                 /** Memoizer for the styles. */
1004                 private final Memoizer<Void> stylesMemoizer = new Memoizer<Void>(new Callable<Void>() {
1005
1006                         @Override
1007                         public Void call() throws Exception {
1008                                 if (!hasValue("styles")) {
1009                                         getValue("styles", Collection.class).set(getStylesByTrack(getId()));
1010                                 }
1011                                 return null;
1012                         }
1013
1014                 });
1015
1016                 /** Memoizer for the remix artists. */
1017                 private final Memoizer<Void> remixArtistsMemoizer = new Memoizer<Void>(new Callable<Void>() {
1018
1019                         @Override
1020                         public Void call() throws Exception {
1021                                 if (!hasValue("remixArtists")) {
1022                                         getValue("remixArtists", List.class).set(getRemixArtistsByTrack(getId()));
1023                                 }
1024                                 return null;
1025                         }
1026
1027                 });
1028
1029                 /** Memoizer for the track derivatives. */
1030                 private final Memoizer<Void> derivativesMemoizer = new Memoizer<Void>(new Callable<Void>() {
1031
1032                         @Override
1033                         public Void call() throws Exception {
1034                                 if (!hasValue("derivatives")) {
1035                                         getValue("derivatives", Collection.class).set(getTrackDerivativesByTrack(getId()));
1036                                 }
1037                                 return null;
1038                         }
1039
1040                 });
1041
1042                 /** Memoizer for the related tracks. */
1043                 private final Memoizer<Void> relatedTracksMemoizer = new Memoizer<Void>(new Callable<Void>() {
1044
1045                         @Override
1046                         public Void call() throws Exception {
1047                                 if (!hasValue("relatedTracks")) {
1048                                         getValue("relatedTracks", Map.class).set(getRelatedTracksByTrack(getId()));
1049                                 }
1050                                 return null;
1051                         }
1052
1053                 });
1054
1055                 /**
1056                  * Creates a new track.
1057                  *
1058                  * @param id
1059                  *            The ID of the track
1060                  */
1061                 public LazyTrack(String id) {
1062                         super(id);
1063                 }
1064
1065                 //
1066                 // DEFAULTTRACK METHODS
1067                 //
1068
1069                 /**
1070                  * {@inheritDoc}
1071                  */
1072                 @Override
1073                 public List<Artist> getArtists() {
1074                         artistsMemoizer.get();
1075                         return super.getArtists();
1076                 }
1077
1078                 /**
1079                  * {@inheritDoc}
1080                  */
1081                 @Override
1082                 public Collection<Style> getStyles() {
1083                         stylesMemoizer.get();
1084                         return super.getStyles();
1085                 }
1086
1087                 /**
1088                  * {@inheritDoc}
1089                  */
1090                 @Override
1091                 public List<Artist> getRemixArtists() {
1092                         remixArtistsMemoizer.get();
1093                         return super.getRemixArtists();
1094                 }
1095
1096                 /**
1097                  * {@inheritDoc}
1098                  */
1099                 @Override
1100                 public Collection<TrackDerivative> getDerivatives() {
1101                         derivativesMemoizer.get();
1102                         return super.getDerivatives();
1103                 }
1104
1105                 /**
1106                  * {@inheritDoc}
1107                  */
1108                 @Override
1109                 public Map<Relationship, Collection<Track>> getRelatedTracks() {
1110                         relatedTracksMemoizer.get();
1111                         return super.getRelatedTracks();
1112                 }
1113
1114                 /**
1115                  * {@inheritDoc}
1116                  */
1117                 @Override
1118                 public Collection<Party> getParties() {
1119                         if (!hasValue("parties")) {
1120                                 try {
1121                                         getValue("parties", Collection.class).set(getPartiesByTrackId(getId()));
1122                                 } catch (DatabaseException de1) {
1123                                         throw new RuntimeException("Could not load Parties for Track " + getId() + ".", de1);
1124                                 }
1125                         }
1126                         return super.getParties();
1127                 }
1128
1129         }
1130
1131         /**
1132          * {@link ObjectCreator} implementation that can create {@link Track}
1133          * objects. This specific implementation creates {@link LazyTrack}
1134          * instances.
1135          *
1136          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
1137          */
1138         private class TrackCreator implements ObjectCreator<Track> {
1139
1140                 /**
1141                  * {@inheritDoc}
1142                  */
1143                 @Override
1144                 public Track createObject(ResultSet resultSet) throws SQLException {
1145                         return new LazyTrack(resultSet.getString("TRACKS.ID")).setName(resultSet.getString("TRACKS.NAME")).setRemix(resultSet.getString("TRACKS.REMIX"));
1146                 }
1147
1148         }
1149
1150         /**
1151          * {@link ObjectCreator} implementation that can create
1152          * {@link TrackDerivative} objects.
1153          *
1154          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
1155          */
1156         private class TrackDerivativeCreator implements ObjectCreator<TrackDerivative> {
1157
1158                 /**
1159                  * {@inheritDoc}
1160                  */
1161                 @Override
1162                 public TrackDerivative createObject(ResultSet resultSet) throws SQLException {
1163                         return new DefaultTrackDerivative(resultSet.getString("TRACK_DERIVATIVES.ID"));
1164                 }
1165
1166         }
1167
1168         /**
1169          * {@link ObjectCreator} implementation that can create {@link Style}
1170          * objects.
1171          *
1172          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
1173          */
1174         private class StyleCreator implements ObjectCreator<Style> {
1175
1176                 /**
1177                  * {@inheritDoc}
1178                  */
1179                 @Override
1180                 public Style createObject(ResultSet resultSet) throws SQLException {
1181                         return new DefaultStyle(resultSet.getString("STYLES.ID")).setName(resultSet.getString("STYLES.NAME"));
1182                 }
1183
1184         }
1185
1186         /**
1187          * {@link Party} implementation that loads additional information only on
1188          * demand.
1189          *
1190          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
1191          */
1192         private class LazyParty extends DefaultParty {
1193
1194                 /**
1195                  * Creates a new party.
1196                  *
1197                  * @param id
1198                  *            The ID of the party
1199                  */
1200                 public LazyParty(String id) {
1201                         super(id);
1202                 }
1203
1204                 //
1205                 // PARTY METHODS
1206                 //
1207
1208                 /**
1209                  * {@inheritDoc}
1210                  */
1211                 @Override
1212                 public Collection<Track> getReleases() {
1213                         if (!hasValue("releases")) {
1214                                 try {
1215                                         getValue("releases", Collection.class).set(getTracksByParty(getId()));
1216                                 } catch (DatabaseException de1) {
1217                                         throw new RuntimeException("Could not loaded Tracks for Party " + getId() + ".", de1);
1218                                 }
1219                         }
1220                         return super.getReleases();
1221                 }
1222
1223         }
1224
1225         /**
1226          * {@link ObjectCreator} implementation that can create {@link Party}
1227          * objects.
1228          *
1229          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
1230          */
1231         private class PartyCreator implements ObjectCreator<Party> {
1232
1233                 /**
1234                  * {@inheritDoc}
1235                  */
1236                 @Override
1237                 public Party createObject(ResultSet resultSet) throws SQLException {
1238                         return new LazyParty(resultSet.getString("PARTIES.ID")).setName(resultSet.getString("PARTIES.NAME"));
1239                 }
1240
1241         }
1242
1243         /**
1244          * {@link User} implementation that retrieves some attributes (such as
1245          * {@link #getOpenIds()}) from the {@link DataManager} on demand.
1246          *
1247          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
1248          */
1249         private class LazyUser extends DefaultUser {
1250
1251                 /** Memoizer for a user’s OpenIDs. */
1252                 private final Memoizer<Void> openIdMemoizer = new Memoizer<Void>(new Callable<Void>() {
1253
1254                         @Override
1255                         public Void call() throws Exception {
1256                                 if (!hasValue("openIds")) {
1257                                         getValue("openIds", Collection.class).set(getOpenIdsByUser(getId()));
1258                                 }
1259                                 return null;
1260                         }
1261                 });
1262
1263                 /**
1264                  * Creates a new user.
1265                  *
1266                  * @param id
1267                  *            The ID of the user
1268                  */
1269                 public LazyUser(String id) {
1270                         super(id);
1271                 }
1272
1273                 /**
1274                  * {@inheritDoc}
1275                  */
1276                 @Override
1277                 public Collection<String> getOpenIds() {
1278                         openIdMemoizer.get();
1279                         return super.getOpenIds();
1280                 }
1281
1282         }
1283
1284         /**
1285          * {@link ObjectCreator} implementation that can create {@link User}
1286          * objects. This specific implementation creates {@link LazyUser} instances.
1287          *
1288          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
1289          */
1290         private class UserCreator implements ObjectCreator<User> {
1291
1292                 /**
1293                  * {@inheritDoc}
1294                  */
1295                 @Override
1296                 public User createObject(ResultSet resultSet) throws SQLException {
1297                         return new LazyUser(resultSet.getString("USERS.ID")).setName(resultSet.getString("USERS.NAME")).setPasswordHash(resultSet.getString("USERS.PASSWORD")).setLevel(resultSet.getInt("USERS.LEVEL"));
1298                 }
1299
1300         }
1301
1302 }