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

   1 /*
   2  * Sone - MemoryDatabase.java - Copyright © 2013–2016 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 import static com.google.common.base.Predicates.not;
  23 import static com.google.common.collect.FluentIterable.from;
  24 import static net.pterodactylus.sone.data.Reply.TIME_COMPARATOR;
  25 import static net.pterodactylus.sone.data.Sone.LOCAL_SONE_FILTER;
  26 import static net.pterodactylus.sone.data.Sone.toAllAlbums;
  27 import static net.pterodactylus.sone.data.Sone.toAllImages;
  28
  29 import java.util.Collection;
  30 import java.util.Collections;
  31 import java.util.Comparator;
  32 import java.util.HashMap;
  33 import java.util.HashSet;
  34 import java.util.List;
  35 import java.util.Map;
  36 import java.util.Set;
  37 import java.util.concurrent.locks.ReadWriteLock;
  38 import java.util.concurrent.locks.ReentrantReadWriteLock;
  39
  40 import javax.annotation.Nonnull;
  41 import javax.annotation.Nullable;
  42
  43 import net.pterodactylus.sone.data.Album;
  44 import net.pterodactylus.sone.data.Image;
  45 import net.pterodactylus.sone.data.Post;
  46 import net.pterodactylus.sone.data.PostReply;
  47 import net.pterodactylus.sone.data.Sone;
  48 import net.pterodactylus.sone.data.impl.AlbumBuilderImpl;
  49 import net.pterodactylus.sone.data.impl.ImageBuilderImpl;
  50 import net.pterodactylus.sone.database.AlbumBuilder;
  51 import net.pterodactylus.sone.database.Database;
  52 import net.pterodactylus.sone.database.DatabaseException;
  53 import net.pterodactylus.sone.database.ImageBuilder;
  54 import net.pterodactylus.sone.database.PostBuilder;
  55 import net.pterodactylus.sone.database.PostDatabase;
  56 import net.pterodactylus.sone.database.PostReplyBuilder;
  57 import net.pterodactylus.sone.database.SoneBuilder;
  58 import net.pterodactylus.sone.database.SoneProvider;
  59 import net.pterodactylus.util.config.Configuration;
  60 import net.pterodactylus.util.config.ConfigurationException;
  61
  62 import com.google.common.base.Optional;
  63 import com.google.common.base.Predicate;
  64 import com.google.common.collect.HashMultimap;
  65 import com.google.common.collect.Multimap;
  66 import com.google.common.collect.SortedSetMultimap;
  67 import com.google.common.collect.TreeMultimap;
  68 import com.google.common.util.concurrent.AbstractService;
  69 import com.google.inject.Inject;
  70 import com.google.inject.Singleton;
  71 import kotlin.jvm.functions.Function1;
  72
  73 /**
  74  * Memory-based {@link PostDatabase} implementation.
  75  *
  76  * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
  77  */
  78 @Singleton
  79 public class MemoryDatabase extends AbstractService implements Database {
  80
  81         /** The lock. */
  82         private final ReadWriteLock lock = new ReentrantReadWriteLock();
  83
  84         /** The Sone provider. */
  85         private final SoneProvider soneProvider;
  86
  87         /** The configuration. */
  88         private final Configuration configuration;
  89         private final ConfigurationLoader configurationLoader;
  90
  91         private final Map<String, Sone> allSones = new HashMap<String, Sone>();
  92
  93         /** All posts by their ID. */
  94         private final Map<String, Post> allPosts = new HashMap<String, Post>();
  95
  96         /** All posts by their Sones. */
  97         private final Multimap<String, Post> sonePosts = HashMultimap.create();
  98
  99         /** Whether posts are known. */
 100         private final Set<String> knownPosts = new HashSet<String>();
 101
 102         /** All post replies by their ID. */
 103         private final Map<String, PostReply> allPostReplies = new HashMap<String, PostReply>();
 104
 105         /** Replies sorted by Sone. */
 106         private final SortedSetMultimap<String, PostReply> sonePostReplies = TreeMultimap.create(new Comparator<String>() {
 107
 108                 @Override
 109                 public int compare(String leftString, String rightString) {
 110                         return leftString.compareTo(rightString);
 111                 }
 112         }, TIME_COMPARATOR);
 113
 114         /** Whether post replies are known. */
 115         private final Set<String> knownPostReplies = new HashSet<String>();
 116
 117         private final Map<String, Album> allAlbums = new HashMap<String, Album>();
 118         private final Multimap<String, Album> soneAlbums = HashMultimap.create();
 119
 120         private final Map<String, Image> allImages = new HashMap<String, Image>();
 121         private final Multimap<String, Image> soneImages = HashMultimap.create();
 122
 123         private final MemoryBookmarkDatabase memoryBookmarkDatabase;
 124         private final MemoryFriendDatabase memoryFriendDatabase;
 125
 126         /**
 127          * Creates a new memory database.
 128          *
 129          * @param soneProvider
 130          *              The Sone provider
 131          * @param configuration
 132          *              The configuration for loading and saving elements
 133          */
 134         @Inject
 135         public MemoryDatabase(SoneProvider soneProvider, Configuration configuration) {
 136                 this.soneProvider = soneProvider;
 137                 this.configuration = configuration;
 138                 this.configurationLoader = new ConfigurationLoader(configuration);
 139                 memoryBookmarkDatabase =
 140                                 new MemoryBookmarkDatabase(this, configurationLoader);
 141                 memoryFriendDatabase = new MemoryFriendDatabase(configurationLoader);
 142         }
 143
 144         //
 145         // DATABASE METHODS
 146         //
 147
 148         /**
 149          * Saves the database.
 150          *
 151          * @throws DatabaseException
 152          *              if an error occurs while saving
 153          */
 154         @Override
 155         public void save() throws DatabaseException {
 156                 saveKnownPosts();
 157                 saveKnownPostReplies();
 158         }
 159
 160         //
 161         // SERVICE METHODS
 162         //
 163
 164         /** {@inheritDocs} */
 165         @Override
 166         protected void doStart() {
 167                 memoryBookmarkDatabase.start();
 168                 loadKnownPosts();
 169                 loadKnownPostReplies();
 170                 notifyStarted();
 171         }
 172
 173         /** {@inheritDocs} */
 174         @Override
 175         protected void doStop() {
 176                 try {
 177                         memoryBookmarkDatabase.stop();
 178                         save();
 179                         notifyStopped();
 180                 } catch (DatabaseException de1) {
 181                         notifyFailed(de1);
 182                 }
 183         }
 184
 185         @Override
 186         public SoneBuilder newSoneBuilder() {
 187                 return new MemorySoneBuilder(this);
 188         }
 189
 190         @Override
 191         public void storeSone(Sone sone) {
 192                 lock.writeLock().lock();
 193                 try {
 194                         removeSone(sone);
 195
 196                         allSones.put(sone.getId(), sone);
 197                         sonePosts.putAll(sone.getId(), sone.getPosts());
 198                         for (Post post : sone.getPosts()) {
 199                                 allPosts.put(post.getId(), post);
 200                         }
 201                         sonePostReplies.putAll(sone.getId(), sone.getReplies());
 202                         for (PostReply postReply : sone.getReplies()) {
 203                                 allPostReplies.put(postReply.getId(), postReply);
 204                         }
 205                         soneAlbums.putAll(sone.getId(), toAllAlbums.apply(sone));
 206                         for (Album album : toAllAlbums.apply(sone)) {
 207                                 allAlbums.put(album.getId(), album);
 208                         }
 209                         soneImages.putAll(sone.getId(), toAllImages.apply(sone));
 210                         for (Image image : toAllImages.apply(sone)) {
 211                                 allImages.put(image.getId(), image);
 212                         }
 213                 } finally {
 214                         lock.writeLock().unlock();
 215                 }
 216         }
 217
 218         @Override
 219         public void removeSone(Sone sone) {
 220                 lock.writeLock().lock();
 221                 try {
 222                         allSones.remove(sone.getId());
 223                         Collection<Post> removedPosts = sonePosts.removeAll(sone.getId());
 224                         for (Post removedPost : removedPosts) {
 225                                 allPosts.remove(removedPost.getId());
 226                         }
 227                         Collection<PostReply> removedPostReplies =
 228                                         sonePostReplies.removeAll(sone.getId());
 229                         for (PostReply removedPostReply : removedPostReplies) {
 230                                 allPostReplies.remove(removedPostReply.getId());
 231                         }
 232                         Collection<Album> removedAlbums =
 233                                         soneAlbums.removeAll(sone.getId());
 234                         for (Album removedAlbum : removedAlbums) {
 235                                 allAlbums.remove(removedAlbum.getId());
 236                         }
 237                         Collection<Image> removedImages =
 238                                         soneImages.removeAll(sone.getId());
 239                         for (Image removedImage : removedImages) {
 240                                 allImages.remove(removedImage.getId());
 241                         }
 242                 } finally {
 243                         lock.writeLock().unlock();
 244                 }
 245         }
 246
 247         @Nonnull
 248         @Override
 249         public Function1<String, Sone> getSoneLoader() {
 250                 return new Function1<String, Sone>() {
 251                         @Override
 252                         public Sone invoke(String soneId) {
 253                                 return getSone(soneId);
 254                         }
 255                 };
 256         }
 257
 258         @Override
 259         public Sone getSone(String soneId) {
 260                 lock.readLock().lock();
 261                 try {
 262                         return allSones.get(soneId);
 263                 } finally {
 264                         lock.readLock().unlock();
 265                 }
 266         }
 267
 268         @Override
 269         public Collection<Sone> getSones() {
 270                 lock.readLock().lock();
 271                 try {
 272                         return new HashSet<Sone>(allSones.values());
 273                 } finally {
 274                         lock.readLock().unlock();
 275                 }
 276         }
 277
 278         @Override
 279         public Collection<Sone> getLocalSones() {
 280                 lock.readLock().lock();
 281                 try {
 282                         return from(allSones.values()).filter(LOCAL_SONE_FILTER).toSet();
 283                 } finally {
 284                         lock.readLock().unlock();
 285                 }
 286         }
 287
 288         @Override
 289         public Collection<Sone> getRemoteSones() {
 290                 lock.readLock().lock();
 291                 try {
 292                         return from(allSones.values())
 293                                         .filter(not(LOCAL_SONE_FILTER)) .toSet();
 294                 } finally {
 295                         lock.readLock().unlock();
 296                 }
 297         }
 298
 299         @Override
 300         public Collection<String> getFriends(Sone localSone) {
 301                 if (!localSone.isLocal()) {
 302                         return Collections.emptySet();
 303                 }
 304                 return memoryFriendDatabase.getFriends(localSone.getId());
 305         }
 306
 307         @Override
 308         public boolean isFriend(Sone localSone, String friendSoneId) {
 309                 if (!localSone.isLocal()) {
 310                         return false;
 311                 }
 312                 return memoryFriendDatabase.isFriend(localSone.getId(), friendSoneId);
 313         }
 314
 315         @Override
 316         public void addFriend(Sone localSone, String friendSoneId) {
 317                 if (!localSone.isLocal()) {
 318                         return;
 319                 }
 320                 memoryFriendDatabase.addFriend(localSone.getId(), friendSoneId);
 321         }
 322
 323         @Override
 324         public void removeFriend(Sone localSone, String friendSoneId) {
 325                 if (!localSone.isLocal()) {
 326                         return;
 327                 }
 328                 memoryFriendDatabase.removeFriend(localSone.getId(), friendSoneId);
 329         }
 330
 331         //
 332         // POSTPROVIDER METHODS
 333         //
 334
 335         /** {@inheritDocs} */
 336         @Override
 337         public Optional<Post> getPost(String postId) {
 338                 lock.readLock().lock();
 339                 try {
 340                         return fromNullable(allPosts.get(postId));
 341                 } finally {
 342                         lock.readLock().unlock();
 343                 }
 344         }
 345
 346         /** {@inheritDocs} */
 347         @Override
 348         public Collection<Post> getPosts(String soneId) {
 349                 return new HashSet<Post>(getPostsFrom(soneId));
 350         }
 351
 352         /** {@inheritDocs} */
 353         @Override
 354         public Collection<Post> getDirectedPosts(final String recipientId) {
 355                 lock.readLock().lock();
 356                 try {
 357                         return from(sonePosts.values()).filter(new Predicate<Post>() {
 358                                 @Override
 359                                 public boolean apply(Post post) {
 360                                         return post.getRecipientId().asSet().contains(recipientId);
 361                                 }
 362                         }).toSet();
 363                 } finally {
 364                         lock.readLock().unlock();
 365                 }
 366         }
 367
 368         //
 369         // POSTBUILDERFACTORY METHODS
 370         //
 371
 372         /** {@inheritDocs} */
 373         @Override
 374         public PostBuilder newPostBuilder() {
 375                 return new MemoryPostBuilder(this, soneProvider);
 376         }
 377
 378         //
 379         // POSTSTORE METHODS
 380         //
 381
 382         /** {@inheritDocs} */
 383         @Override
 384         public void storePost(Post post) {
 385                 checkNotNull(post, "post must not be null");
 386                 lock.writeLock().lock();
 387                 try {
 388                         allPosts.put(post.getId(), post);
 389                         getPostsFrom(post.getSone().getId()).add(post);
 390                 } finally {
 391                         lock.writeLock().unlock();
 392                 }
 393         }
 394
 395         /** {@inheritDocs} */
 396         @Override
 397         public void removePost(Post post) {
 398                 checkNotNull(post, "post must not be null");
 399                 lock.writeLock().lock();
 400                 try {
 401                         allPosts.remove(post.getId());
 402                         getPostsFrom(post.getSone().getId()).remove(post);
 403                         post.getSone().removePost(post);
 404                 } finally {
 405                         lock.writeLock().unlock();
 406                 }
 407         }
 408
 409         //
 410         // POSTREPLYPROVIDER METHODS
 411         //
 412
 413         @Nullable
 414         @Override
 415         public PostReply getPostReply(String id) {
 416                 lock.readLock().lock();
 417                 try {
 418                         return allPostReplies.get(id);
 419                 } finally {
 420                         lock.readLock().unlock();
 421                 }
 422         }
 423
 424         /** {@inheritDocs} */
 425         @Override
 426         public List<PostReply> getReplies(final String postId) {
 427                 lock.readLock().lock();
 428                 try {
 429                         return from(allPostReplies.values())
 430                                         .filter(new Predicate<PostReply>() {
 431                                                 @Override
 432                                                 public boolean apply(PostReply postReply) {
 433                                                         return postReply.getPostId().equals(postId);
 434                                                 }
 435                                         }).toSortedList(TIME_COMPARATOR);
 436                 } finally {
 437                         lock.readLock().unlock();
 438                 }
 439         }
 440
 441         //
 442         // POSTREPLYBUILDERFACTORY METHODS
 443         //
 444
 445         /** {@inheritDocs} */
 446         @Override
 447         public PostReplyBuilder newPostReplyBuilder() {
 448                 return new MemoryPostReplyBuilder(this, soneProvider);
 449         }
 450
 451         //
 452         // POSTREPLYSTORE METHODS
 453         //
 454
 455         /** {@inheritDocs} */
 456         @Override
 457         public void storePostReply(PostReply postReply) {
 458                 lock.writeLock().lock();
 459                 try {
 460                         allPostReplies.put(postReply.getId(), postReply);
 461                 } finally {
 462                         lock.writeLock().unlock();
 463                 }
 464         }
 465
 466         /** {@inheritDocs} */
 467         @Override
 468         public void removePostReply(PostReply postReply) {
 469                 lock.writeLock().lock();
 470                 try {
 471                         allPostReplies.remove(postReply.getId());
 472                 } finally {
 473                         lock.writeLock().unlock();
 474                 }
 475         }
 476
 477         //
 478         // ALBUMPROVDER METHODS
 479         //
 480
 481         @Override
 482         public Optional<Album> getAlbum(String albumId) {
 483                 lock.readLock().lock();
 484                 try {
 485                         return fromNullable(allAlbums.get(albumId));
 486                 } finally {
 487                         lock.readLock().unlock();
 488                 }
 489         }
 490
 491         //
 492         // ALBUMBUILDERFACTORY METHODS
 493         //
 494
 495         @Override
 496         public AlbumBuilder newAlbumBuilder() {
 497                 return new AlbumBuilderImpl();
 498         }
 499
 500         //
 501         // ALBUMSTORE METHODS
 502         //
 503
 504         @Override
 505         public void storeAlbum(Album album) {
 506                 lock.writeLock().lock();
 507                 try {
 508                         allAlbums.put(album.getId(), album);
 509                         soneAlbums.put(album.getSone().getId(), album);
 510                 } finally {
 511                         lock.writeLock().unlock();
 512                 }
 513         }
 514
 515         @Override
 516         public void removeAlbum(Album album) {
 517                 lock.writeLock().lock();
 518                 try {
 519                         allAlbums.remove(album.getId());
 520                         soneAlbums.remove(album.getSone().getId(), album);
 521                 } finally {
 522                         lock.writeLock().unlock();
 523                 }
 524         }
 525
 526         //
 527         // IMAGEPROVIDER METHODS
 528         //
 529
 530         @Override
 531         public Optional<Image> getImage(String imageId) {
 532                 lock.readLock().lock();
 533                 try {
 534                         return fromNullable(allImages.get(imageId));
 535                 } finally {
 536                         lock.readLock().unlock();
 537                 }
 538         }
 539
 540         //
 541         // IMAGEBUILDERFACTORY METHODS
 542         //
 543
 544         @Override
 545         public ImageBuilder newImageBuilder() {
 546                 return new ImageBuilderImpl();
 547         }
 548
 549         //
 550         // IMAGESTORE METHODS
 551         //
 552
 553         @Override
 554         public void storeImage(Image image) {
 555                 lock.writeLock().lock();
 556                 try {
 557                         allImages.put(image.getId(), image);
 558                         soneImages.put(image.getSone().getId(), image);
 559                 } finally {
 560                         lock.writeLock().unlock();
 561                 }
 562         }
 563
 564         @Override
 565         public void removeImage(Image image) {
 566                 lock.writeLock().lock();
 567                 try {
 568                         allImages.remove(image.getId());
 569                         soneImages.remove(image.getSone().getId(), image);
 570                 } finally {
 571                         lock.writeLock().unlock();
 572                 }
 573         }
 574
 575         @Override
 576         public void bookmarkPost(Post post) {
 577                 memoryBookmarkDatabase.bookmarkPost(post);
 578         }
 579
 580         @Override
 581         public void unbookmarkPost(Post post) {
 582                 memoryBookmarkDatabase.unbookmarkPost(post);
 583         }
 584
 585         @Override
 586         public boolean isPostBookmarked(Post post) {
 587                 return memoryBookmarkDatabase.isPostBookmarked(post);
 588         }
 589
 590         @Override
 591         public Set<Post> getBookmarkedPosts() {
 592                 return memoryBookmarkDatabase.getBookmarkedPosts();
 593         }
 594
 595         //
 596         // PACKAGE-PRIVATE METHODS
 597         //
 598
 599         /**
 600          * Returns whether the given post is known.
 601          *
 602          * @param post
 603          *              The post
 604          * @return {@code true} if the post is known, {@code false} otherwise
 605          */
 606         boolean isPostKnown(Post post) {
 607                 lock.readLock().lock();
 608                 try {
 609                         return knownPosts.contains(post.getId());
 610                 } finally {
 611                         lock.readLock().unlock();
 612                 }
 613         }
 614
 615         /**
 616          * Sets whether the given post is known.
 617          *
 618          * @param post
 619          *              The post
 620          * @param known
 621          *              {@code true} if the post is known, {@code false} otherwise
 622          */
 623         void setPostKnown(Post post, boolean known) {
 624                 lock.writeLock().lock();
 625                 try {
 626                         if (known) {
 627                                 knownPosts.add(post.getId());
 628                         } else {
 629                                 knownPosts.remove(post.getId());
 630                         }
 631                 } finally {
 632                         lock.writeLock().unlock();
 633                 }
 634         }
 635
 636         /**
 637          * Returns whether the given post reply is known.
 638          *
 639          * @param postReply
 640          *              The post reply
 641          * @return {@code true} if the given post reply is known, {@code false}
 642          *         otherwise
 643          */
 644         boolean isPostReplyKnown(PostReply postReply) {
 645                 lock.readLock().lock();
 646                 try {
 647                         return knownPostReplies.contains(postReply.getId());
 648                 } finally {
 649                         lock.readLock().unlock();
 650                 }
 651         }
 652
 653         /**
 654          * Sets whether the given post reply is known.
 655          *
 656          * @param postReply
 657          *              The post reply
 658          * @param known
 659          *              {@code true} if the post reply is known, {@code false} otherwise
 660          */
 661         void setPostReplyKnown(PostReply postReply, boolean known) {
 662                 lock.writeLock().lock();
 663                 try {
 664                         if (known) {
 665                                 knownPostReplies.add(postReply.getId());
 666                         } else {
 667                                 knownPostReplies.remove(postReply.getId());
 668                         }
 669                 } finally {
 670                         lock.writeLock().unlock();
 671                 }
 672         }
 673
 674         //
 675         // PRIVATE METHODS
 676         //
 677
 678         /**
 679          * Gets all posts for the given Sone, creating a new collection if there is
 680          * none yet.
 681          *
 682          * @param soneId
 683          *              The ID of the Sone to get the posts for
 684          * @return All posts
 685          */
 686         private Collection<Post> getPostsFrom(String soneId) {
 687                 lock.readLock().lock();
 688                 try {
 689                         return sonePosts.get(soneId);
 690                 } finally {
 691                         lock.readLock().unlock();
 692                 }
 693         }
 694
 695         /** Loads the known posts. */
 696         private void loadKnownPosts() {
 697                 Set<String> knownPosts = configurationLoader.loadKnownPosts();
 698                 lock.writeLock().lock();
 699                 try {
 700                         this.knownPosts.clear();
 701                         this.knownPosts.addAll(knownPosts);
 702                 } finally {
 703                         lock.writeLock().unlock();
 704                 }
 705         }
 706
 707         /**
 708          * Saves the known posts to the configuration.
 709          *
 710          * @throws DatabaseException
 711          *              if a configuration error occurs
 712          */
 713         private void saveKnownPosts() throws DatabaseException {
 714                 lock.readLock().lock();
 715                 try {
 716                         int postCounter = 0;
 717                         for (String knownPostId : knownPosts) {
 718                                 configuration.getStringValue("KnownPosts/" + postCounter++ + "/ID").setValue(knownPostId);
 719                         }
 720                         configuration.getStringValue("KnownPosts/" + postCounter + "/ID").setValue(null);
 721                 } catch (ConfigurationException ce1) {
 722                         throw new DatabaseException("Could not save database.", ce1);
 723                 } finally {
 724                         lock.readLock().unlock();
 725                 }
 726         }
 727
 728         /** Loads the known post replies. */
 729         private void loadKnownPostReplies() {
 730                 Set<String> knownPostReplies = configurationLoader.loadKnownPostReplies();
 731                 lock.writeLock().lock();
 732                 try {
 733                         this.knownPostReplies.clear();
 734                         this.knownPostReplies.addAll(knownPostReplies);
 735                 } finally {
 736                         lock.writeLock().unlock();
 737                 }
 738         }
 739
 740         /**
 741          * Saves the known post replies to the configuration.
 742          *
 743          * @throws DatabaseException
 744          *              if a configuration error occurs
 745          */
 746         private void saveKnownPostReplies() throws DatabaseException {
 747                 lock.readLock().lock();
 748                 try {
 749                         int replyCounter = 0;
 750                         for (String knownReplyId : knownPostReplies) {
 751                                 configuration.getStringValue("KnownReplies/" + replyCounter++ + "/ID").setValue(knownReplyId);
 752                         }
 753                         configuration.getStringValue("KnownReplies/" + replyCounter + "/ID").setValue(null);
 754                 } catch (ConfigurationException ce1) {
 755                         throw new DatabaseException("Could not save database.", ce1);
 756                 } finally {
 757                         lock.readLock().unlock();
 758                 }
 759         }
 760
 761 }