src/main/java/net/pterodactylus/sone/database/memory/MemoryDatabase.java

   1 /*
   2  * Sone - MemoryDatabase.java - Copyright © 2013 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.sone.database.memory;
  19
  20 import static com.google.common.base.Optional.fromNullable;
  21 import static com.google.common.base.Preconditions.checkNotNull;
  22
  23 import java.util.ArrayList;
  24 import java.util.Collection;
  25 import java.util.Collections;
  26 import java.util.Comparator;
  27 import java.util.HashMap;
  28 import java.util.HashSet;
  29 import java.util.List;
  30 import java.util.Map;
  31 import java.util.Set;
  32 import java.util.SortedSet;
  33 import java.util.TreeSet;
  34 import java.util.concurrent.locks.ReadWriteLock;
  35 import java.util.concurrent.locks.ReentrantReadWriteLock;
  36
  37 import net.pterodactylus.sone.data.Album;
  38 import net.pterodactylus.sone.data.Image;
  39 import net.pterodactylus.sone.data.Post;
  40 import net.pterodactylus.sone.data.PostReply;
  41 import net.pterodactylus.sone.data.Reply;
  42 import net.pterodactylus.sone.data.Sone;
  43 import net.pterodactylus.sone.database.Database;
  44 import net.pterodactylus.sone.database.DatabaseException;
  45 import net.pterodactylus.sone.database.PostBuilder;
  46 import net.pterodactylus.sone.database.PostDatabase;
  47 import net.pterodactylus.sone.database.PostReplyBuilder;
  48 import net.pterodactylus.sone.database.SoneProvider;
  49 import net.pterodactylus.util.config.Configuration;
  50 import net.pterodactylus.util.config.ConfigurationException;
  51
  52 import com.google.common.base.Optional;
  53 import com.google.common.collect.ArrayListMultimap;
  54 import com.google.common.collect.ListMultimap;
  55 import com.google.common.collect.SortedSetMultimap;
  56 import com.google.common.collect.TreeMultimap;
  57 import com.google.common.util.concurrent.AbstractService;
  58 import com.google.inject.Inject;
  59
  60 /**
  61  * Memory-based {@link PostDatabase} implementation.
  62  *
  63  * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
  64  */
  65 public class MemoryDatabase extends AbstractService implements Database {
  66
  67         /** The lock. */
  68         private final ReadWriteLock lock = new ReentrantReadWriteLock();
  69
  70         /** The Sone provider. */
  71         private final SoneProvider soneProvider;
  72
  73         /** The configuration. */
  74         private final Configuration configuration;
  75
  76         /** All posts by their ID. */
  77         private final Map<String, Post> allPosts = new HashMap<String, Post>();
  78
  79         /** All posts by their Sones. */
  80         private final Map<String, Collection<Post>> sonePosts = new HashMap<String, Collection<Post>>();
  81
  82         /** All posts by their recipient. */
  83         private final Map<String, Collection<Post>> recipientPosts = new HashMap<String, Collection<Post>>();
  84
  85         /** Whether posts are known. */
  86         private final Set<String> knownPosts = new HashSet<String>();
  87
  88         /** All post replies by their ID. */
  89         private final Map<String, PostReply> allPostReplies = new HashMap<String, PostReply>();
  90
  91         /** Replies sorted by Sone. */
  92         private final SortedSetMultimap<String, PostReply> sonePostReplies = TreeMultimap.create(new Comparator<String>() {
  93
  94                 @Override
  95                 public int compare(String leftString, String rightString) {
  96                         return leftString.compareTo(rightString);
  97                 }
  98         }, PostReply.TIME_COMPARATOR);
  99
 100         /** Replies by post. */
 101         private final Map<String, SortedSet<PostReply>> postReplies = new HashMap<String, SortedSet<PostReply>>();
 102
 103         /** Whether post replies are known. */
 104         private final Set<String> knownPostReplies = new HashSet<String>();
 105
 106         private final Map<String, Album> allAlbums = new HashMap<String, Album>();
 107         private final ListMultimap<String, String> albumChildren = ArrayListMultimap.create();
 108         private final ListMultimap<String, String> albumImages = ArrayListMultimap.create();
 109
 110         private final Map<String, Image> allImages = new HashMap<String, Image>();
 111
 112         /**
 113          * Creates a new memory database.
 114          *
 115          * @param soneProvider
 116          *              The Sone provider
 117          * @param configuration
 118          *              The configuration for loading and saving elements
 119          */
 120         @Inject
 121         public MemoryDatabase(SoneProvider soneProvider, Configuration configuration) {
 122                 this.soneProvider = soneProvider;
 123                 this.configuration = configuration;
 124         }
 125
 126         //
 127         // DATABASE METHODS
 128         //
 129
 130         /**
 131          * Saves the database.
 132          *
 133          * @throws DatabaseException
 134          *              if an error occurs while saving
 135          */
 136         @Override
 137         public void save() throws DatabaseException {
 138                 saveKnownPosts();
 139                 saveKnownPostReplies();
 140         }
 141
 142         //
 143         // SERVICE METHODS
 144         //
 145
 146         /** {@inheritDocs} */
 147         @Override
 148         protected void doStart() {
 149                 loadKnownPosts();
 150                 loadKnownPostReplies();
 151                 notifyStarted();
 152         }
 153
 154         /** {@inheritDocs} */
 155         @Override
 156         protected void doStop() {
 157                 try {
 158                         save();
 159                         notifyStopped();
 160                 } catch (DatabaseException de1) {
 161                         notifyFailed(de1);
 162                 }
 163         }
 164
 165         //
 166         // POSTPROVIDER METHODS
 167         //
 168
 169         /** {@inheritDocs} */
 170         @Override
 171         public Optional<Post> getPost(String postId) {
 172                 lock.readLock().lock();
 173                 try {
 174                         return fromNullable(allPosts.get(postId));
 175                 } finally {
 176                         lock.readLock().unlock();
 177                 }
 178         }
 179
 180         /** {@inheritDocs} */
 181         @Override
 182         public Collection<Post> getPosts(String soneId) {
 183                 return new HashSet<Post>(getPostsFrom(soneId));
 184         }
 185
 186         /** {@inheritDocs} */
 187         @Override
 188         public Collection<Post> getDirectedPosts(String recipientId) {
 189                 lock.readLock().lock();
 190                 try {
 191                         Collection<Post> posts = recipientPosts.get(recipientId);
 192                         return (posts == null) ? Collections.<Post>emptySet() : new HashSet<Post>(posts);
 193                 } finally {
 194                         lock.readLock().unlock();
 195                 }
 196         }
 197
 198         //
 199         // POSTBUILDERFACTORY METHODS
 200         //
 201
 202         /** {@inheritDocs} */
 203         @Override
 204         public PostBuilder newPostBuilder() {
 205                 return new MemoryPostBuilder(this);
 206         }
 207
 208         //
 209         // POSTSTORE METHODS
 210         //
 211
 212         /** {@inheritDocs} */
 213         @Override
 214         public void storePost(Post post) {
 215                 checkNotNull(post, "post must not be null");
 216                 lock.writeLock().lock();
 217                 try {
 218                         allPosts.put(post.getId(), post);
 219                         getPostsFrom(post.getSone().getId()).add(post);
 220                         if (post.getRecipientId().isPresent()) {
 221                                 getPostsTo(post.getRecipientId().get()).add(post);
 222                         }
 223                 } finally {
 224                         lock.writeLock().unlock();
 225                 }
 226         }
 227
 228         /** {@inheritDocs} */
 229         @Override
 230         public void removePost(Post post) {
 231                 checkNotNull(post, "post must not be null");
 232                 lock.writeLock().lock();
 233                 try {
 234                         allPosts.remove(post.getId());
 235                         getPostsFrom(post.getSone().getId()).remove(post);
 236                         if (post.getRecipientId().isPresent()) {
 237                                 getPostsTo(post.getRecipientId().get()).remove(post);
 238                         }
 239                         post.getSone().removePost(post);
 240                 } finally {
 241                         lock.writeLock().unlock();
 242                 }
 243         }
 244
 245         /** {@inheritDocs} */
 246         @Override
 247         public void storePosts(Sone sone, Collection<Post> posts) throws IllegalArgumentException {
 248                 checkNotNull(sone, "sone must not be null");
 249                 /* verify that all posts are from the same Sone. */
 250                 for (Post post : posts) {
 251                         if (!sone.equals(post.getSone())) {
 252                                 throw new IllegalArgumentException(String.format("Post from different Sone found: %s", post));
 253                         }
 254                 }
 255
 256                 lock.writeLock().lock();
 257                 try {
 258                         /* remove all posts by the Sone. */
 259                         getPostsFrom(sone.getId()).clear();
 260                         for (Post post : posts) {
 261                                 allPosts.remove(post.getId());
 262                                 if (post.getRecipientId().isPresent()) {
 263                                         getPostsTo(post.getRecipientId().get()).remove(post);
 264                                 }
 265                         }
 266
 267                         /* add new posts. */
 268                         getPostsFrom(sone.getId()).addAll(posts);
 269                         for (Post post : posts) {
 270                                 allPosts.put(post.getId(), post);
 271                                 if (post.getRecipientId().isPresent()) {
 272                                         getPostsTo(post.getRecipientId().get()).add(post);
 273                                 }
 274                         }
 275                 } finally {
 276                         lock.writeLock().unlock();
 277                 }
 278         }
 279
 280         /** {@inheritDocs} */
 281         @Override
 282         public void removePosts(Sone sone) {
 283                 checkNotNull(sone, "sone must not be null");
 284                 lock.writeLock().lock();
 285                 try {
 286                         /* remove all posts by the Sone. */
 287                         getPostsFrom(sone.getId()).clear();
 288                         for (Post post : sone.getPosts()) {
 289                                 allPosts.remove(post.getId());
 290                                 if (post.getRecipientId().isPresent()) {
 291                                         getPostsTo(post.getRecipientId().get()).remove(post);
 292                                 }
 293                         }
 294                 } finally {
 295                         lock.writeLock().unlock();
 296                 }
 297         }
 298
 299         //
 300         // POSTREPLYPROVIDER METHODS
 301         //
 302
 303         /** {@inheritDocs} */
 304         @Override
 305         public Optional<PostReply> getPostReply(String id) {
 306                 lock.readLock().lock();
 307                 try {
 308                         return fromNullable(allPostReplies.get(id));
 309                 } finally {
 310                         lock.readLock().unlock();
 311                 }
 312         }
 313
 314         /** {@inheritDocs} */
 315         @Override
 316         public List<PostReply> getReplies(String postId) {
 317                 lock.readLock().lock();
 318                 try {
 319                         if (!postReplies.containsKey(postId)) {
 320                                 return Collections.emptyList();
 321                         }
 322                         return new ArrayList<PostReply>(postReplies.get(postId));
 323                 } finally {
 324                         lock.readLock().unlock();
 325                 }
 326         }
 327
 328         //
 329         // POSTREPLYBUILDERFACTORY METHODS
 330         //
 331
 332         /** {@inheritDocs} */
 333         @Override
 334         public PostReplyBuilder newPostReplyBuilder() {
 335                 return new MemoryPostReplyBuilder(this, soneProvider);
 336         }
 337
 338         //
 339         // POSTREPLYSTORE METHODS
 340         //
 341
 342         /** {@inheritDocs} */
 343         @Override
 344         public void storePostReply(PostReply postReply) {
 345                 lock.writeLock().lock();
 346                 try {
 347                         allPostReplies.put(postReply.getId(), postReply);
 348                         if (postReplies.containsKey(postReply.getPostId())) {
 349                                 postReplies.get(postReply.getPostId()).add(postReply);
 350                         } else {
 351                                 TreeSet<PostReply> replies = new TreeSet<PostReply>(Reply.TIME_COMPARATOR);
 352                                 replies.add(postReply);
 353                                 postReplies.put(postReply.getPostId(), replies);
 354                         }
 355                 } finally {
 356                         lock.writeLock().unlock();
 357                 }
 358         }
 359
 360         /** {@inheritDocs} */
 361         @Override
 362         public void storePostReplies(Sone sone, Collection<PostReply> postReplies) {
 363                 checkNotNull(sone, "sone must not be null");
 364                 /* verify that all posts are from the same Sone. */
 365                 for (PostReply postReply : postReplies) {
 366                         if (!sone.equals(postReply.getSone())) {
 367                                 throw new IllegalArgumentException(String.format("PostReply from different Sone found: %s", postReply));
 368                         }
 369                 }
 370
 371                 lock.writeLock().lock();
 372                 try {
 373                         /* remove all post replies of the Sone. */
 374                         for (PostReply postReply : getRepliesFrom(sone.getId())) {
 375                                 removePostReply(postReply);
 376                         }
 377                         for (PostReply postReply : postReplies) {
 378                                 allPostReplies.put(postReply.getId(), postReply);
 379                                 sonePostReplies.put(postReply.getSone().getId(), postReply);
 380                                 if (this.postReplies.containsKey(postReply.getPostId())) {
 381                                         this.postReplies.get(postReply.getPostId()).add(postReply);
 382                                 } else {
 383                                         TreeSet<PostReply> replies = new TreeSet<PostReply>(Reply.TIME_COMPARATOR);
 384                                         replies.add(postReply);
 385                                         this.postReplies.put(postReply.getPostId(), replies);
 386                                 }
 387                         }
 388                 } finally {
 389                         lock.writeLock().unlock();
 390                 }
 391         }
 392
 393         /** {@inheritDocs} */
 394         @Override
 395         public void removePostReply(PostReply postReply) {
 396                 lock.writeLock().lock();
 397                 try {
 398                         allPostReplies.remove(postReply.getId());
 399                         if (postReplies.containsKey(postReply.getPostId())) {
 400                                 postReplies.get(postReply.getPostId()).remove(postReply);
 401                                 if (postReplies.get(postReply.getPostId()).isEmpty()) {
 402                                         postReplies.remove(postReply.getPostId());
 403                                 }
 404                         }
 405                 } finally {
 406                         lock.writeLock().unlock();
 407                 }
 408         }
 409
 410         /** {@inheritDocs} */
 411         @Override
 412         public void removePostReplies(Sone sone) {
 413                 checkNotNull(sone, "sone must not be null");
 414
 415                 lock.writeLock().lock();
 416                 try {
 417                         for (PostReply postReply : sone.getReplies()) {
 418                                 removePostReply(postReply);
 419                         }
 420                 } finally {
 421                         lock.writeLock().unlock();
 422                 }
 423         }
 424
 425         //
 426         // ALBUMPROVDER METHODS
 427         //
 428
 429         @Override
 430         public Optional<Album> getAlbum(String albumId) {
 431                 lock.readLock().lock();
 432                 try {
 433                         return fromNullable(allAlbums.get(albumId));
 434                 } finally {
 435                         lock.readLock().unlock();
 436                 }
 437         }
 438
 439         //
 440         // ALBUMSTORE METHODS
 441         //
 442
 443         @Override
 444         public void storeAlbum(Album album) {
 445                 lock.writeLock().lock();
 446                 try {
 447                         allAlbums.put(album.getId(), album);
 448                         albumChildren.put(album.getParent().getId(), album.getId());
 449                 } finally {
 450                         lock.writeLock().unlock();
 451                 }
 452         }
 453
 454         @Override
 455         public void removeAlbum(Album album) {
 456                 lock.writeLock().lock();
 457                 try {
 458                         allAlbums.remove(album.getId());
 459                         albumChildren.remove(album.getParent().getId(), album.getId());
 460                 } finally {
 461                         lock.writeLock().unlock();
 462                 }
 463         }
 464
 465         //
 466         // IMAGEPROVIDER METHODS
 467         //
 468
 469         @Override
 470         public Optional<Image> getImage(String imageId) {
 471                 lock.readLock().lock();
 472                 try {
 473                         return fromNullable(allImages.get(imageId));
 474                 } finally {
 475                         lock.readLock().unlock();
 476                 }
 477         }
 478
 479         //
 480         // IMAGESTORE METHODS
 481         //
 482
 483         @Override
 484         public void storeImage(Image image) {
 485                 lock.writeLock().lock();
 486                 try {
 487                         allImages.put(image.getId(), image);
 488                         albumImages.put(image.getAlbum().getId(), image.getId());
 489                 } finally {
 490                         lock.writeLock().unlock();
 491                 }
 492         }
 493
 494         @Override
 495         public void removeImage(Image image) {
 496                 lock.writeLock().lock();
 497                 try {
 498                         allImages.remove(image.getId());
 499                         albumImages.remove(image.getAlbum().getId(), image.getId());
 500                 } finally {
 501                         lock.writeLock().unlock();
 502                 }
 503         }
 504
 505         //
 506         // PACKAGE-PRIVATE METHODS
 507         //
 508
 509         /**
 510          * Returns whether the given post is known.
 511          *
 512          * @param post
 513          *              The post
 514          * @return {@code true} if the post is known, {@code false} otherwise
 515          */
 516         boolean isPostKnown(Post post) {
 517                 lock.readLock().lock();
 518                 try {
 519                         return knownPosts.contains(post.getId());
 520                 } finally {
 521                         lock.readLock().unlock();
 522                 }
 523         }
 524
 525         /**
 526          * Sets whether the given post is known.
 527          *
 528          * @param post
 529          *              The post
 530          * @param known
 531          *              {@code true} if the post is known, {@code false} otherwise
 532          */
 533         void setPostKnown(Post post, boolean known) {
 534                 lock.writeLock().lock();
 535                 try {
 536                         if (known) {
 537                                 knownPosts.add(post.getId());
 538                         } else {
 539                                 knownPosts.remove(post.getId());
 540                         }
 541                 } finally {
 542                         lock.writeLock().unlock();
 543                 }
 544         }
 545
 546         /**
 547          * Returns whether the given post reply is known.
 548          *
 549          * @param postReply
 550          *              The post reply
 551          * @return {@code true} if the given post reply is known, {@code false}
 552          *         otherwise
 553          */
 554         boolean isPostReplyKnown(PostReply postReply) {
 555                 lock.readLock().lock();
 556                 try {
 557                         return knownPostReplies.contains(postReply.getId());
 558                 } finally {
 559                         lock.readLock().unlock();
 560                 }
 561         }
 562
 563         /**
 564          * Sets whether the given post reply is known.
 565          *
 566          * @param postReply
 567          *              The post reply
 568          * @param known
 569          *              {@code true} if the post reply is known, {@code false} otherwise
 570          */
 571         void setPostReplyKnown(PostReply postReply, boolean known) {
 572                 lock.writeLock().lock();
 573                 try {
 574                         if (known) {
 575                                 knownPostReplies.add(postReply.getId());
 576                         } else {
 577                                 knownPostReplies.remove(postReply.getId());
 578                         }
 579                 } finally {
 580                         lock.writeLock().unlock();
 581                 }
 582         }
 583
 584         void moveUp(Album album) {
 585                 lock.writeLock().lock();
 586                 try {
 587                         List<String> albums = albumChildren.get(album.getParent().getId());
 588                         int currentIndex = albums.indexOf(album.getId());
 589                         if (currentIndex == 0) {
 590                                 return;
 591                         }
 592                         albums.remove(album.getId());
 593                         albums.add(currentIndex - 1, album.getId());
 594                 } finally {
 595                         lock.writeLock().unlock();
 596                 }
 597         }
 598
 599         void moveDown(Album album) {
 600                 lock.writeLock().lock();
 601                 try {
 602                         List<String> albums = albumChildren.get(album.getParent().getId());
 603                         int currentIndex = albums.indexOf(album.getId());
 604                         if (currentIndex == (albums.size() - 1)) {
 605                                 return;
 606                         }
 607                         albums.remove(album.getId());
 608                         albums.add(currentIndex + 1, album.getId());
 609                 } finally {
 610                         lock.writeLock().unlock();
 611                 }
 612         }
 613
 614         void moveUp(Image image) {
 615                 lock.writeLock().lock();
 616                 try {
 617                         List<String> images = albumImages.get(image.getAlbum().getId());
 618                         int currentIndex = images.indexOf(image.getId());
 619                         if (currentIndex == 0) {
 620                                 return;
 621                         }
 622                         images.remove(image.getId());
 623                         images.add(currentIndex - 1, image.getId());
 624                 } finally {
 625                         lock.writeLock().unlock();
 626                 }
 627         }
 628
 629         void moveDown(Image image) {
 630                 lock.writeLock().lock();
 631                 try {
 632                         List<String> images = albumChildren.get(image.getAlbum().getId());
 633                         int currentIndex = images.indexOf(image.getId());
 634                         if (currentIndex == (images.size() - 1)) {
 635                                 return;
 636                         }
 637                         images.remove(image.getId());
 638                         images.add(currentIndex + 1, image.getId());
 639                 } finally {
 640                         lock.writeLock().unlock();
 641                 }
 642         }
 643
 644         //
 645         // PRIVATE METHODS
 646         //
 647
 648         /**
 649          * Gets all posts for the given Sone, creating a new collection if there is
 650          * none yet.
 651          *
 652          * @param soneId
 653          *              The ID of the Sone to get the posts for
 654          * @return All posts
 655          */
 656         private Collection<Post> getPostsFrom(String soneId) {
 657                 Collection<Post> posts = null;
 658                 lock.readLock().lock();
 659                 try {
 660                         posts = sonePosts.get(soneId);
 661                 } finally {
 662                         lock.readLock().unlock();
 663                 }
 664                 if (posts != null) {
 665                         return posts;
 666                 }
 667
 668                 posts = new HashSet<Post>();
 669                 lock.writeLock().lock();
 670                 try {
 671                         sonePosts.put(soneId, posts);
 672                 } finally {
 673                         lock.writeLock().unlock();
 674                 }
 675
 676                 return posts;
 677         }
 678
 679         /**
 680          * Gets all posts that are directed the given Sone, creating a new collection
 681          * if there is none yet.
 682          *
 683          * @param recipientId
 684          *              The ID of the Sone to get the posts for
 685          * @return All posts
 686          */
 687         private Collection<Post> getPostsTo(String recipientId) {
 688                 Collection<Post> posts = null;
 689                 lock.readLock().lock();
 690                 try {
 691                         posts = recipientPosts.get(recipientId);
 692                 } finally {
 693                         lock.readLock().unlock();
 694                 }
 695                 if (posts != null) {
 696                         return posts;
 697                 }
 698
 699                 posts = new HashSet<Post>();
 700                 lock.writeLock().lock();
 701                 try {
 702                         recipientPosts.put(recipientId, posts);
 703                 } finally {
 704                         lock.writeLock().unlock();
 705                 }
 706
 707                 return posts;
 708         }
 709
 710         /** Loads the known posts. */
 711         private void loadKnownPosts() {
 712                 lock.writeLock().lock();
 713                 try {
 714                         int postCounter = 0;
 715                         while (true) {
 716                                 String knownPostId = configuration.getStringValue("KnownPosts/" + postCounter++ + "/ID").getValue(null);
 717                                 if (knownPostId == null) {
 718                                         break;
 719                                 }
 720                                 knownPosts.add(knownPostId);
 721                         }
 722                 } finally {
 723                         lock.writeLock().unlock();
 724                 }
 725         }
 726
 727         /**
 728          * Saves the known posts to the configuration.
 729          *
 730          * @throws DatabaseException
 731          *              if a configuration error occurs
 732          */
 733         private void saveKnownPosts() throws DatabaseException {
 734                 lock.readLock().lock();
 735                 try {
 736                         int postCounter = 0;
 737                         for (String knownPostId : knownPosts) {
 738                                 configuration.getStringValue("KnownPosts/" + postCounter++ + "/ID").setValue(knownPostId);
 739                         }
 740                         configuration.getStringValue("KnownPosts/" + postCounter + "/ID").setValue(null);
 741                 } catch (ConfigurationException ce1) {
 742                         throw new DatabaseException("Could not save database.", ce1);
 743                 } finally {
 744                         lock.readLock().unlock();
 745                 }
 746         }
 747
 748         /**
 749          * Returns all replies by the given Sone.
 750          *
 751          * @param id
 752          *              The ID of the Sone
 753          * @return The post replies of the Sone, sorted by time (newest first)
 754          */
 755         private Collection<PostReply> getRepliesFrom(String id) {
 756                 lock.readLock().lock();
 757                 try {
 758                         if (sonePostReplies.containsKey(id)) {
 759                                 return Collections.unmodifiableCollection(sonePostReplies.get(id));
 760                         }
 761                         return Collections.emptySet();
 762                 } finally {
 763                         lock.readLock().unlock();
 764                 }
 765         }
 766
 767         /** Loads the known post replies. */
 768         private void loadKnownPostReplies() {
 769                 lock.writeLock().lock();
 770                 try {
 771                         int replyCounter = 0;
 772                         while (true) {
 773                                 String knownReplyId = configuration.getStringValue("KnownReplies/" + replyCounter++ + "/ID").getValue(null);
 774                                 if (knownReplyId == null) {
 775                                         break;
 776                                 }
 777                                 knownPostReplies.add(knownReplyId);
 778                         }
 779                 } finally {
 780                         lock.writeLock().unlock();
 781                 }
 782         }
 783
 784         /**
 785          * Saves the known post replies to the configuration.
 786          *
 787          * @throws DatabaseException
 788          *              if a configuration error occurs
 789          */
 790         private void saveKnownPostReplies() throws DatabaseException {
 791                 lock.readLock().lock();
 792                 try {
 793                         int replyCounter = 0;
 794                         for (String knownReplyId : knownPostReplies) {
 795                                 configuration.getStringValue("KnownReplies/" + replyCounter++ + "/ID").setValue(knownReplyId);
 796                         }
 797                         configuration.getStringValue("KnownReplies/" + replyCounter + "/ID").setValue(null);
 798                 } catch (ConfigurationException ce1) {
 799                         throw new DatabaseException("Could not save database.", ce1);
 800                 } finally {
 801                         lock.readLock().unlock();
 802                 }
 803         }
 804
 805 }