Make LocalDB thread safe and simplify its API

client/src/main/java/envoy/client/data/LocalDB.java

@@ -30,59 +30,55 @@ import dev.kske.eventbus.EventListener;
  */
 public final class LocalDB implements EventListener {
 
+	// Data
 	private User				user;
-	private Map<String, User>	users		= new HashMap<>();
+	private Map<String, User>	users		= Collections.synchronizedMap(new HashMap<>());
-	private List<Chat>			chats		= new ArrayList<>();
+	private List<Chat>			chats		= Collections.synchronizedList(new ArrayList<>());
 	private IDGenerator			idGenerator;
 	private CacheMap			cacheMap	= new CacheMap();
-	private Instant				lastSync	= Instant.EPOCH;
 	private String				authToken;
-	private File				dbDir, userFile, idGeneratorFile, lastLoginFile, usersFile;
+
-	private FileLock			instanceLock;
+	// State management
+	private Instant lastSync = Instant.EPOCH;
+
+	// Persistence
+	private File		dbDir, userFile, idGeneratorFile, lastLoginFile, usersFile;
+	private FileLock	instanceLock;
 
 	/**
 	 * Constructs an empty local database. To serialize any user-specific data to
-	 * the file system, call {@link LocalDB#initializeUserStorage()} first
+	 * the file system, call {@link LocalDB#save(boolean)}.
-	 * and then {@link LocalDB#save(boolean)}.
 	 *
 	 * @param dbDir the directory in which to persist data
-	 * @throws IOException if {@code dbDir} is a file (and not a directory)
+	 * @throws IOException    if {@code dbDir} is a file (and not a directory)
+	 * @throws EnvoyException if {@code dbDir} is in use by another Envoy instance
 	 * @since Envoy Client v0.2-beta
 	 */
-	public LocalDB(File dbDir) throws IOException {
+	public LocalDB(File dbDir) throws IOException, EnvoyException {
 		this.dbDir = dbDir;
 		EventBus.getInstance().registerListener(this);
 
 		// Ensure that the database directory exists
 		if (!dbDir.exists()) {
 			dbDir.mkdirs();
-		} else if (!dbDir.isDirectory())
+		} else if (!dbDir.isDirectory()) throw new IOException(String.format("LocalDBDir '%s' is not a directory!", dbDir.getAbsolutePath()));
-			throw new IOException(String.format("LocalDBDir '%s' is not a directory!", dbDir.getAbsolutePath()));
 
+		// Lock the directory
+		lock();
 
 		// Initialize global files
 		idGeneratorFile	= new File(dbDir, "id_gen.db");
 		lastLoginFile	= new File(dbDir, "last_login.db");
 		usersFile		= new File(dbDir, "users.db");
 
+		// Load global files
+		loadGlobalData();
+
 		// Initialize offline caches
 		cacheMap.put(Message.class, new Cache<>());
 		cacheMap.put(MessageStatusChange.class, new Cache<>());
 	}
 
-	/**
-	 * Creates a database file for a user-specific list of chats.
-	 *
-	 * @throws IllegalStateException if the client user is not specified
-	 * @since Envoy Client v0.1-alpha
-	 */
-	public void initializeUserStorage() {
-		if (user == null) throw new IllegalStateException("Client user is null, cannot initialize user storage");
-		userFile = new File(dbDir, user.getID() + ".db");
-	}
-
-	FileChannel fc;
-
 	/**
 	 * Ensured that only one Envoy instance is using this local database by creating
 	 * a lock file.
@@ -91,9 +87,8 @@ public final class LocalDB implements EventListener {
 	 * @throws EnvoyException if the lock cannot by acquired
 	 * @since Envoy Client v0.2-beta
 	 */
-	public void lock() throws EnvoyException {
+	private synchronized void lock() throws EnvoyException {
 		File file = new File(dbDir, "instance.lock");
-		file.deleteOnExit();
 		try {
 			FileChannel fc = FileChannel.open(file.toPath(), StandardOpenOption.CREATE, StandardOpenOption.WRITE);
 			instanceLock = fc.tryLock();
@@ -104,37 +99,24 @@ public final class LocalDB implements EventListener {
 	}
 
 	/**
-	 * Stores all users. If the client user is specified, their chats will be stored
+	 * Loads the local user registry {@code users.db}, the id generator
-	 * as well. The message id generator will also be saved if present.
+	 * {@code id_gen.db} and last login file {@code last_login.db}.
 	 *
-	 * @param isOnline determines which {@code lastSync} time stamp is saved
+	 * @since Envoy Client v0.2-beta
-	 * @throws IOException if the saving process failed
-	 * @since Envoy Client v0.3-alpha
 	 */
-	public void save(boolean isOnline) throws IOException {
+	private synchronized void loadGlobalData() {
-
+		try {
-		// Save users
+			try (var in = new ObjectInputStream(new FileInputStream(usersFile))) {
-		SerializationUtils.write(usersFile, users);
+				users = (Map<String, User>) in.readObject();
-
+			}
-		// Save user data and last sync time stamp
+			idGenerator = SerializationUtils.read(idGeneratorFile, IDGenerator.class);
-		if (user != null) SerializationUtils.write(userFile, chats, cacheMap, isOnline ? Instant.now() : lastSync);
+			try (var in = new ObjectInputStream(new FileInputStream(lastLoginFile))) {
-
+				user		= (User) in.readObject();
-		// Save last login information
+				authToken	= (String) in.readObject();
-		if (authToken != null) SerializationUtils.write(lastLoginFile, user, authToken);
+			}
-
+		} catch (IOException | ClassNotFoundException e) {}
-		// Save id generator
-		if (hasIDGenerator()) SerializationUtils.write(idGeneratorFile, idGenerator);
 	}
 
-	/**
-	 * Loads all user data.
-	 *
-	 * @throws ClassNotFoundException if the loading process failed
-	 * @throws IOException            if the loading process failed
-	 * @since Envoy Client v0.3-alpha
-	 */
-	public void loadUsers() throws ClassNotFoundException, IOException { users = SerializationUtils.read(usersFile, HashMap.class); }
-
 	/**
 	 * Loads all data of the client user.
 	 *
@@ -142,36 +124,15 @@ public final class LocalDB implements EventListener {
 	 * @throws IOException            if the loading process failed
 	 * @since Envoy Client v0.3-alpha
 	 */
-	public void loadUserData() throws ClassNotFoundException, IOException {
+	public synchronized void loadUserData() throws ClassNotFoundException, IOException {
+		if (user == null) throw new IllegalStateException("Client user is null, cannot initialize user storage");
+		userFile = new File(dbDir, user.getID() + ".db");
 		try (var in = new ObjectInputStream(new FileInputStream(userFile))) {
-			chats		= (ArrayList<Chat>) in.readObject();
+			chats		= (List<Chat>) in.readObject();
 			cacheMap	= (CacheMap) in.readObject();
 			lastSync	= (Instant) in.readObject();
 		}
-	}
+		synchronize();
-
-	/**
-	 * Loads the ID generator. Any exception thrown during this process is ignored.
-	 *
-	 * @since Envoy Client v0.3-alpha
-	 */
-	public void loadIDGenerator() {
-		try {
-			idGenerator = SerializationUtils.read(idGeneratorFile, IDGenerator.class);
-		} catch (ClassNotFoundException | IOException e) {}
-	}
-
-	/**
-	 * Loads the last login information. Any exception thrown during this process is
-	 * ignored.
-	 *
-	 * @since Envoy Client v0.2-beta
-	 */
-	public void loadLastLogin() {
-		try (var in = new ObjectInputStream(new FileInputStream(lastLoginFile))) {
-			user		= (User) in.readObject();
-			authToken	= (String) in.readObject();
-		} catch (ClassNotFoundException | IOException e) {}
 	}
 
 	/**
@@ -180,7 +141,7 @@ public final class LocalDB implements EventListener {
 	 *
 	 * @since Envoy Client v0.1-beta
 	 */
-	public void synchronize() {
+	private void synchronize() {
 		user.getContacts().stream().filter(u -> u instanceof User && !users.containsKey(u.getName())).forEach(u -> users.put(u.getName(), (User) u));
 		users.put(user.getName(), user);
 
@@ -197,11 +158,33 @@ public final class LocalDB implements EventListener {
 			.forEach(chats::add);
 	}
 
-	@Event
+	/**
-	private void onNewAuthToken(NewAuthToken evt) {
+	 * Stores all users. If the client user is specified, their chats will be stored
-		authToken = evt.get();
+	 * as well. The message id generator will also be saved if present.
+	 *
+	 * @param isOnline determines which {@code lastSync} time stamp is saved
+	 * @throws IOException if the saving process failed
+	 * @since Envoy Client v0.3-alpha
+	 */
+	public synchronized void save(boolean isOnline) throws IOException {
+
+		// Save users
+		SerializationUtils.write(usersFile, users);
+
+		// Save user data and last sync time stamp
+		if (user != null) SerializationUtils.write(userFile, chats, cacheMap, isOnline ? Instant.now() : lastSync);
+
+		// Save last login information
+		if (authToken != null) SerializationUtils.write(lastLoginFile, user, authToken);
+
+		// Save id generator
+		if (hasIDGenerator()) SerializationUtils.write(idGeneratorFile, idGenerator);
 	}
 
+
+	@Event
+	private void onNewAuthToken(NewAuthToken evt) { authToken = evt.get(); }
+
 	/**
 	 * @return a {@code Map<String, User>} of all users stored locally with their
 	 *         user names as keys

client/src/main/java/envoy/client/ui/Startup.java

@@ -70,7 +70,6 @@ public final class Startup extends Application {
 			File localDBDir = new File(config.getHomeDirectory(), config.getLocalDB().getPath());
 			logger.info("Initializing LocalDB at " + localDBDir);
 			localDB = new LocalDB(localDBDir);
-			localDB.lock();
 		} catch (IOException | EnvoyException e) {
 			logger.log(Level.SEVERE, "Could not initialize local database: ", e);
 			new Alert(AlertType.ERROR, "Could not initialize local database!\n" + e).showAndWait();
@@ -79,8 +78,6 @@ public final class Startup extends Application {
 		}
 
 		// Prepare handshake
-		localDB.loadIDGenerator();
-		localDB.loadLastLogin();
 		context.setLocalDB(localDB);
 
 		// Configure stage
@@ -94,7 +91,6 @@ public final class Startup extends Application {
 		// Authenticate with token if present
 		if (localDB.getAuthToken() != null) {
 			logger.info("Attempting authentication with token...");
-			localDB.initializeUserStorage();
 			localDB.loadUserData();
 			if (!performHandshake(
 					LoginCredentials.loginWithToken(localDB.getUser().getName(), localDB.getAuthToken(), VERSION, localDB.getLastSync())))
@@ -146,7 +142,6 @@ public final class Startup extends Application {
 	public static boolean attemptOfflineMode(String identifier) {
 		try {
 			// Try entering offline mode
-			localDB.loadUsers();
 			final User clientUser = localDB.getUsers().get(identifier);
 			if (clientUser == null) throw new EnvoyException("Could not enter offline mode: user name unknown");
 			client.setSender(clientUser);
@@ -169,9 +164,7 @@ public final class Startup extends Application {
 	 */
 	public static Instant loadLastSync(String identifier) {
 		try {
-			localDB.loadUsers();
 			localDB.setUser(localDB.getUsers().get(identifier));
-			localDB.initializeUserStorage();
 			localDB.loadUserData();
 		} catch (final Exception e) {
 			// User storage empty, wrong user name etc. -> default lastSync
@@ -186,7 +179,6 @@ public final class Startup extends Application {
 
 		// Initialize chats in local database
 		try {
-			localDB.initializeUserStorage();
 			localDB.loadUserData();
 		} catch (final FileNotFoundException e) {
 			// The local database file has not yet been created, probably first login
@@ -196,7 +188,6 @@ public final class Startup extends Application {
 		}
 
 		context.initWriteProxy();
-		localDB.synchronize();
 
 		if (client.isOnline()) context.getWriteProxy().flushCache();
 		else