Merge branch 'develop' into f/primaryComponents

src/main/java/envoy/client/Client.java

@@ -1,6 +1,7 @@
 package envoy.client;
 
-import java.util.logging.Logger;
+import java.util.HashMap;
+import java.util.Map;
 
 import javax.ws.rs.client.ClientBuilder;
 import javax.ws.rs.client.Entity;
@@ -10,6 +11,7 @@ import javax.xml.bind.JAXBContext;
 import javax.xml.bind.JAXBException;
 import javax.xml.bind.Marshaller;
 
+import envoy.exception.EnvoyException;
 import envoy.schema.ObjectFactory;
 import envoy.schema.Sync;
 import envoy.schema.User;
@@ -29,14 +31,28 @@ public class Client {
 	private ObjectFactory	objectFactory	= new ObjectFactory();
 	private Config			config;
 	private User			sender, recipient;
+	private boolean			online			= false;
 
-	private static final Logger logger = Logger.getLogger(Client.class.getSimpleName());
+	/**
+	 * Initializes the client. At this state, the client user has yet to be
+	 * initialized, which can be done by calling {@link Client#onlineInit(String).
+	 * 
+	 * @param config The {@link Config} instance to use in this client
+	 * @since Envoy v0.2-alpha
+	 */
+	public Client(Config config) { this.config = config; }
 
-	public Client(Config config, String username) {
+	/**
-		this.config	= config;
+	 * Enters the online mode by acquiring a user ID from the server.
-		sender		= getUser(username);
+	 * 
-
+	 * @param userName the name of the client user
-		logger.info("ID: " + sender.getID());
+	 * @throws EnvoyException if the online mode could not be entered or the request
+	 *                        failed for some other reason
+	 * @since Envoy v0.2-alpha
+	 */
+	public void onlineInit(String userName) throws EnvoyException {
+		sender	= getUser(userName);
+		online	= true;
 	}
 
 	private <T, R> R post(String uri, T body, Class<R> responseBodyClass) {
@@ -48,28 +64,26 @@ public class Client {
 		client.close();
 
 		return responseBody;
-
 	}
 
 	/**
-	 * Returns a {@link Sync} with all users on the server.
+	 * @return a {@code Map<String, User>} of all users on the server with their
-	 * 
+	 *         user names as keys
-	 * @return Sync - List of all users on the server.
+	 * @since Envoy v0.2-alpha
-	 * @since Envoy v0.1-alpha
 	 */
-	public Sync getUsersListXml() {
+	public Map<String, User> getUsers() {
 		Sync	sendSync	= objectFactory.createSync();
 		User	user		= objectFactory.createUser();
 		user.setID(-1);
 		sendSync.getUsers().add(user);
 
-		Sync returnSendSync = post(
+		Sync returnSync = post(String.format("%s:%d/envoy-server/rest/sync/syncData?userId=%d", config.getServer(), config.getPort(), 0),
-				String
-					.format("%s:%d/envoy-server/rest/sync/syncData?userId=%d", config.getServer(), config.getPort(), 0),
 				sendSync,
 				Sync.class);
-		return returnSendSync;
 
+		Map<String, User> users = new HashMap<>();
+		returnSync.getUsers().forEach(u -> users.put(u.getName(), u));
+		return users;
 	}
 
 	/**
@@ -77,29 +91,29 @@ public class Client {
 	 * 
 	 * @param name - the name of the {@link User}
 	 * @return a {@link User} with the specified name
+	 * @throws EnvoyException if the server does not return the requested ID
 	 * @since Envoy v0.1-alpha
 	 */
-	private User getUser(String name) {
+	private User getUser(String name) throws EnvoyException {
+		// Create a sync with only a user with the requested name
 		Sync	senderSync	= objectFactory.createSync();
 		User	user		= objectFactory.createUser();
 		user.setName(name);
 		senderSync.getUsers().add(user);
 
-		Sync returnSenderSync = post(
+		try {
-				String
+			Sync sync = post(String.format("%s:%d/envoy-server/rest/sync/syncData?userId=%d", config.getServer(), config.getPort(), 0),
-					.format("%s:%d/envoy-server/rest/sync/syncData?userId=%d", config.getServer(), config.getPort(), 0),
+					senderSync,
-				senderSync,
+					Sync.class);
-				Sync.class);
 
-		User returnSender = objectFactory.createUser();
+			// Expecting a single user with an ID
-
+			if (sync.getUsers().size() == 1) {
-		if (returnSenderSync.getUsers().size() == 1) {
+				online = true;
-			returnSender = returnSenderSync.getUsers().get(0);
+				return sync.getUsers().get(0);
-		} else {
+			} else throw new EnvoyException("Unexpected response from Envoy Server");
-			logger.warning("ERROR exiting...");
+		} catch (Exception e) {
+			throw new EnvoyException("Could not connect to server", e);
 		}
-
-		return returnSender;
 	}
 
 	/**
@@ -134,11 +148,15 @@ public class Client {
 	 * their updated UserStatus to the client.) <br>
 	 * 
 	 * @param userId the id of the {@link Client} who sends the {@link Sync}
-	 * @param sync the sync object (yet to be converted from java class to sync.xml)
+	 * @param sync   the sync object (yet to be converted from java class to
+	 *               sync.xml)
 	 * @return a returnSync.xml file
+	 * @throws EnvoyException if the client is not in online mode
 	 * @since Envoy v0.1-alpha
 	 */
-	public Sync sendSync(long userId, Sync sync) {
+	public Sync sendSync(long userId, Sync sync) throws EnvoyException {
+		if(!isOnline())
+			throw new EnvoyException("Client is not in online mode");
 		// Print sync XML to console
 		JAXBContext jc;
 		try {
@@ -151,10 +169,7 @@ public class Client {
 		}
 
 		// Send sync
-		return post(String
+		return post(String.format("%s:%d/envoy-server/rest/sync/syncData?userId=%d", config.getServer(), config.getPort(), userId), sync, Sync.class);
-			.format("%s:%d/envoy-server/rest/sync/syncData?userId=%d", config.getServer(), config.getPort(), userId),
-				sync,
-				Sync.class);
 	}
 
 	/**
@@ -163,6 +178,14 @@ public class Client {
 	 */
 	public User getSender() { return sender; }
 
+	/**
+	 * Sets the client user which is used to send messages.
+	 * 
+	 * @param sender the client user to set
+	 * @since Envoy v0.2-alpha
+	 */
+	public void setSender(User sender) { this.sender = sender; }
+
 	/**
 	 * @return the current recipient of the current chat.
 	 * @since Envoy v0.1-alpha
@@ -172,7 +195,7 @@ public class Client {
 	/**
 	 * Sets the recipient.
 	 * 
-	 * @param recipient - the recipient to set
+	 * @param recipient the recipient to set
 	 * @since Envoy v0.1-alpha
 	 */
 	public void setRecipient(User recipient) { this.recipient = recipient; }
@@ -182,4 +205,10 @@ public class Client {
 	 * @since Envoy v0.1-alpha
 	 */
 	public boolean hasRecipient() { return recipient != null; }
+
+	/**
+	 * @return {@code true} if a connection to the server could be established
+	 * @since Envoy v0.2-alpha
+	 */
+	public boolean isOnline() { return online; }
 }

src/main/java/envoy/client/Config.java

@@ -3,6 +3,8 @@ package envoy.client;
 import java.io.File;
 import java.util.Properties;
 
+import envoy.exception.EnvoyException;
+
 /**
  * Project: <strong>envoy-client</strong><br>
  * File: <strong>Config.java</strong><br>
@@ -29,17 +31,26 @@ public class Config {
 
 	/**
 	 * Defaults to the {@code client.properties} file for information.
+	 * This file contains information about
+	 * the server and port, as well as the path to the local
+	 * database and the synchronization timeout
 	 * 
-	 * @param properties a {@link Properties} object containing information about
+	 * @throws EnvoyException if the {@code client.properties} file could not be
-	 *                   the server and port, as well as the path to the local
+	 *                        loaded
-	 *                   database and the synchronization timeout
 	 * @since Envoy v0.1-alpha
 	 */
-	public void load(Properties properties) {
+	public void load() throws EnvoyException {
-		if (properties.containsKey("server")) server = properties.getProperty("server");
+		ClassLoader loader = getClass().getClassLoader();
-		if (properties.containsKey("port")) port = Integer.parseInt(properties.getProperty("port"));
+		try {
-		localDB		= new File(properties.getProperty("localDB", ".\\localDB"));
+			Properties properties = new Properties();
-		syncTimeout	= Integer.parseInt(properties.getProperty("syncTimeout", "1000"));
+			properties.load(loader.getResourceAsStream("client.properties"));
+			if (properties.containsKey("server")) server = properties.getProperty("server");
+			if (properties.containsKey("port")) port = Integer.parseInt(properties.getProperty("port"));
+			localDB		= new File(properties.getProperty("localDB", ".\\localDB"));
+			syncTimeout	= Integer.parseInt(properties.getProperty("syncTimeout", "1000"));
+		} catch (Exception e) {
+			throw new EnvoyException("Failed to load client.properties", e);
+		}
 	}
 
 	/**
@@ -47,9 +58,10 @@ public class Config {
 	 * -s, --port / -p and --localDB / -db.
 	 * 
 	 * @param args the command line arguments to parse
+	 * @throws EnvoyException if the command line arguments contain an unknown token
 	 * @since Envoy v0.1-alpha
 	 */
-	public void load(String[] args) {
+	public void load(String[] args) throws EnvoyException {
 		for (int i = 0; i < args.length; i++)
 			switch (args[i]) {
 				case "--server":
@@ -64,6 +76,8 @@ public class Config {
 				case "-db":
 					localDB = new File(args[++i]);
 					break;
+				default:
+					throw new EnvoyException("Unknown token " + args[i] + " found");
 			}
 	}
 
@@ -71,9 +85,7 @@ public class Config {
 	 * @return {@code true} if server, port and localDB directory are known.
 	 * @since Envoy v0.1-alpha
 	 */
-	public boolean isInitialized() {
+	public boolean isInitialized() { return server != null && !server.isEmpty() && port > 0 && port < 65566 && localDB != null; }
-		return server != null && !server.isEmpty() && port > 0 && port < 65566 && localDB != null;
-	}
 
 	/**
 	 * @return the host name of the Envoy server
@@ -114,7 +126,7 @@ public class Config {
 	/**
 	 * Changes the default local database.
 	 * Exclusively intended for development purposes.
-   	 *
+	 *
 	 * @param localDB the file containing the local database
 	 * @since Envoy v0.1-alpha
 	 **/

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

@@ -8,7 +8,9 @@ import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
 import java.time.Instant;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.logging.Logger;
 
 import javax.xml.datatype.DatatypeConfigurationException;
@@ -34,9 +36,11 @@ import envoy.schema.User;
  */
 public class LocalDB {
 
-	private File			localDB;
+	private File				localDBDir, localDBFile, usersFile;
-	private User			sender;
+	private User				user;
-	private List<Chat>		chats			= new ArrayList<>();
+	private Map<String, User>	users	= new HashMap<>();
+	private List<Chat>			chats	= new ArrayList<>();
+
 	private ObjectFactory	objectFactory	= new ObjectFactory();
 	private DatatypeFactory	datatypeFactory;
 
@@ -47,64 +51,91 @@ public class LocalDB {
 	private static final Logger logger = Logger.getLogger(LocalDB.class.getSimpleName());
 
 	/**
-	 * Constructs an empty local database.
+	 * Constructs an empty local database. To serialize any chats to the file
+	 * system, call {@link LocalDB#initializeDBFile(File)}.
 	 *
-	 * @param sender the user that is logged in with this client
+	 * @param localDBDir the directory in which to store users and chats
 	 * @since Envoy v0.1-alpha
 	 */
-	public LocalDB(User sender) {
+	public LocalDB(File localDBDir) throws IOException {
-		this.sender = sender;
+		this.localDBDir = localDBDir;
+
 		try {
 			datatypeFactory = DatatypeFactory.newInstance();
 		} catch (DatatypeConfigurationException e) {
 			e.printStackTrace();
 		}
+
+		// Initialize local database directory
+		if (localDBDir.exists() && !localDBDir.isDirectory())
+			throw new IOException(String.format("LocalDBDir '%s' is not a directory!", localDBDir.getAbsolutePath()));
+		usersFile = new File(localDBDir, "users.db");
 	}
 
 	/**
-	 * Initializes the local database and fills it with values
+	 * Creates a database file for a user-specific list of chats.
-	 * if the user has already sent or received messages.
 	 *
-	 * @param localDBDir the directory where we wish to save/load the database from.
+	 * @throws NullPointerException if the client user is not yet specified
-	 * @throws EnvoyException if the directory selected is not an actual directory.
 	 * @since Envoy v0.1-alpha
 	 */
-	public void initializeDBFile(File localDBDir) throws EnvoyException {
+	public void initializeDBFile() {
-		if (localDBDir.exists() && !localDBDir.isDirectory())
+		if (user == null) throw new NullPointerException("Client user is null");
-			throw new EnvoyException(String.format("LocalDBDir '%s' is not a directory!", localDBDir.getAbsolutePath()));
+		localDBFile = new File(localDBDir, user.getID() + ".db");
-		localDB = new File(localDBDir, sender.getID() + ".db");
-		if (localDB.exists()) loadFromLocalDB();
 	}
 
 	/**
-	 * Saves the database into a file for future use.
+	 * Stores all users to the local database. If the client user is specified, the
+	 * chats related to this user are stored as well.
 	 *
 	 * @throws IOException if something went wrong during saving
 	 * @since Envoy v0.1-alpha
 	 */
-	public void saveToLocalDB() throws IOException {
+	public void save() throws IOException {
-		localDB.getParentFile().mkdirs();
+		// Save users
-		localDB.createNewFile();
+		write(usersFile, users);
-		try (ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(localDB))) {
+
-			out.writeObject(chats);
+		// Save chats
-		} catch (IOException ex) {
+		write(localDBFile, chats);
-			throw ex;
-		}
 	}
 
+	/**
+	 * Loads all users that are stored in the local database.
+	 * 
+	 * @throws EnvoyException if the loading process failed
+	 * @since Envoy v0.2-alpha
+	 */
+	@SuppressWarnings("unchecked")
+	public void loadUsers() throws EnvoyException { users = read(usersFile, HashMap.class); }
+
 	/**
 	 * Loads all chats saved by Envoy for the client user.
 	 *
-	 * @throws EnvoyException if something fails while loading.
+	 * @throws EnvoyException if the loading process failed
 	 * @since Envoy v0.1-alpha
 	 */
 	@SuppressWarnings("unchecked")
-	private void loadFromLocalDB() throws EnvoyException {
+	public void loadChats() throws EnvoyException { chats = read(localDBFile, ArrayList.class); }
-		try (ObjectInputStream in = new ObjectInputStream(new FileInputStream(localDB))) {
+
-			Object obj = in.readObject();
+	private <T> T read(File file, Class<T> serializedClass) throws EnvoyException {
-			if (obj instanceof ArrayList<?>) chats = (ArrayList<Chat>) obj;
+		if (file == null) throw new NullPointerException("File is null");
+		try (ObjectInputStream in = new ObjectInputStream(new FileInputStream(file))) {
+			return serializedClass.cast(in.readObject());
 		} catch (ClassNotFoundException | IOException e) {
-			throw new EnvoyException(e);
+			throw new EnvoyException("Could not load serialized object", e);
+		}
+	}
+
+	private <T> void write(File file, T obj) throws IOException {
+		if (file == null) throw new NullPointerException("File is null");
+		if (obj == null) throw new NullPointerException("Object to serialize is null");
+		if (!file.exists()) {
+			file.getParentFile().mkdirs();
+			file.createNewFile();
+		}
+		try (ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(file))) {
+			out.writeObject(obj);
+		} catch (IOException e) {
+			throw e;
 		}
 	}
 
@@ -118,7 +149,7 @@ public class LocalDB {
 	 */
 	public Message createMessage(String textContent, long recipientID) {
 		Message.Metadata metaData = objectFactory.createMessageMetadata();
-		metaData.setSender(sender.getID());
+		metaData.setSender(user.getID());
 		metaData.setRecipient(recipientID);
 		metaData.setState(MessageState.WAITING);
 		metaData.setDate(datatypeFactory.newXMLGregorianCalendar(Instant.now().toString()));
@@ -280,6 +311,17 @@ public class LocalDB {
 	 */
 	public void clearUnreadMessagesSync() { unreadMessagesSync.getMessages().clear(); }
 
+	/**
+	 * @return a {@code Map<String, User>} of all users stored locally with their user names as keys
+	 * @since Envoy v0.2-alpha
+	 */
+	public Map<String, User> getUsers() { return users; }
+
+	/**
+	 * @param users the users to set
+	 */
+	public void setUsers(Map<String, User> users) { this.users = users; }
+
 	/**
 	 * @return all saved {@link Chat} objects that list the client user as the
 	 *         sender
@@ -288,8 +330,19 @@ public class LocalDB {
 	public List<Chat> getChats() { return chats; }
 
 	/**
-	 * @return the {@link User} who initialized the local database
+	 * @param chats the chats to set
-	 * @since Envoy v0.1-alpha
 	 */
-	public User getUser() { return sender; }
+	public void setChats(List<Chat> chats) { this.chats = chats; }
+
+	/**
+	 * @return the {@link User} who initialized the local database
+	 * @since Envoy v0.2-alpha
+	 */
+	public User getUser() { return user; }
+
+	/**
+	 * @param user the user to set
+	 * @since Envoy v0.2-alpha
+	 */
+	public void setUser(User user) { this.user = user; }
 }

src/main/java/envoy/client/Settings.java

@@ -26,8 +26,6 @@ import envoy.client.ui.Theme;
 public class Settings {
 
 	// Actual settings accessible by the rest of the application
-	private String				username;
-	private String				email;
 	private boolean				enterToSend	= true;
 	private Map<String, Theme>	themes;
 	private String				currentTheme;
@@ -65,8 +63,6 @@ public class Settings {
 
 	@SuppressWarnings("unchecked")
 	private void load() {
-		setUsername(prefs.get("username", ""));
-		setEmail(prefs.get("email", ""));
 		setEnterToSend(prefs.getBoolean("enterToSend", true));
 		setCurrentTheme(prefs.get("theme", "dark"));
 
@@ -90,14 +86,12 @@ public class Settings {
 	}
 
 	/**
-	 * updates prefs when save button is clicked
+	 * Updates the preferences when the save button is clicked.
 	 * 
 	 * @throws IOException
 	 * @since Envoy v0.2-alpha
 	 */
 	public void save() throws IOException {
-		prefs.put("username", getUsername());
-		prefs.put("email", getEmail());
 		prefs.put("theme", currentTheme);
 		prefs.putBoolean("enterToSend", isEnterToSend());
 
@@ -133,30 +127,6 @@ public class Settings {
 	 */
 	public void setCurrentTheme(String themeName) { currentTheme = themeName; }
 
-	/**
-	 * @return the user name
-	 * @since Envoy v0.2-alpha
-	 */
-	public String getUsername() { return username; }
-
-	/**
-	 * @param username the user name to set
-	 * @since Envoy v0.2-alpha
-	 */
-	public void setUsername(String username) { this.username = username; }
-
-	/**
-	 * @return the email associated with that user.
-	 * @since Envoy v0.2-alpha
-	 */
-	public String getEmail() { return email; }
-
-	/**
-	 * @param email the email to set
-	 * @since Envoy v0.2-alpha
-	 */
-	public void setEmail(String email) { this.email = email; }
-
 	/**
 	 * @return true, if "enter" suffices to send a message, else it has to be "ctrl"
 	 *         + "enter"

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

@@ -32,7 +32,6 @@ import envoy.client.Config;
 import envoy.client.LocalDB;
 import envoy.client.Settings;
 import envoy.schema.Message;
-import envoy.schema.Sync;
 import envoy.schema.User;
 
 /**
@@ -84,7 +83,7 @@ public class ChatWindow extends JFrame {
 			@Override
 			public void windowClosing(WindowEvent evt) {
 				try {
-					localDB.saveToLocalDB();
+					localDB.save();
 					Settings.getInstance().save();
 				} catch (IOException e1) {
 					e1.printStackTrace();
@@ -228,7 +227,8 @@ public class ChatWindow extends JFrame {
 		contentPane.revalidate();
 
 		loadUsersAndChats();
-		startSyncThread(Config.getInstance().getSyncTimeout());
+
+		if (client.isOnline()) startSyncThread(Config.getInstance().getSyncTimeout());
 
 		contentPane.revalidate();
 	}
@@ -305,9 +305,8 @@ public class ChatWindow extends JFrame {
 	 */
 	private void loadUsersAndChats() {
 		new Thread(() -> {
-			Sync					users			= client.getUsersListXml();
+			DefaultListModel<User> userListModel = new DefaultListModel<>();
-			DefaultListModel<User>	userListModel	= new DefaultListModel<>();
+			localDB.getUsers().values().forEach(user -> {
-			users.getUsers().forEach(user -> {
 				userListModel.addElement(user);
 
 				// Check if user exists in local DB
@@ -331,7 +330,11 @@ public class ChatWindow extends JFrame {
 			new Thread(() -> {
 
 				// Synchronize
-				localDB.applySync(client.sendSync(client.getSender().getID(), localDB.fillSync(client.getSender().getID())));
+				try {
+					localDB.applySync(client.sendSync(client.getSender().getID(), localDB.fillSync(client.getSender().getID())));
+				} catch (Exception e) {
+					logger.log(Level.SEVERE, "Could not perform sync", e);
+				}
 
 				// Process unread messages
 				localDB.addUnreadMessagesToLocalDB();

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

@@ -303,10 +303,6 @@ public class SettingsScreen extends JDialog {
 				getRootPane().setDefaultButton(okButton);
 				okButton.addActionListener((evt) -> {
 					try {
-						Settings.getInstance().setUsername(Settings.getInstance().getUsername());// still temporary
-
-						Settings.getInstance().setEmail(Settings.getInstance().getEmail());// still temporary value
-
 						Settings.getInstance().setEnterToSend(Settings.getInstance().isEnterToSend());// still temporary
 
 						Settings.getInstance().setCurrentTheme(selectedTheme.getThemeName());

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

@@ -2,7 +2,6 @@ package envoy.client.ui;
 
 import java.awt.EventQueue;
 import java.io.IOException;
-import java.util.Properties;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -11,12 +10,12 @@ import javax.swing.JOptionPane;
 import envoy.client.Client;
 import envoy.client.Config;
 import envoy.client.LocalDB;
-import envoy.client.Settings;
 import envoy.exception.EnvoyException;
+import envoy.schema.User;
 
 /**
  * Starts the Envoy client and prompts the user to enter their name.
- * 
+ * <br>
  * Project: <strong>envoy-client</strong><br>
  * File: <strong>Startup.java</strong><br>
  * Created: <strong>12 Oct 2019</strong><br>
@@ -35,34 +34,69 @@ public class Startup {
 
 		Config config = Config.getInstance();
 
-		// Load the configuration from client.properties first
-		ClassLoader loader = Thread.currentThread().getContextClassLoader();
 		try {
-			Properties configProperties = new Properties();
+			// Load the configuration from client.properties first
-			configProperties.load(loader.getResourceAsStream("client.properties"));
+			config.load();
-			config.load(configProperties);
+
-		} catch (IOException e) {
+			// Override configuration values with command line arguments
+			if (args.length > 0) config.load(args);
+
+			// Check if all configuration values have been initialized
+			if (!config.isInitialized()) throw new EnvoyException("Server or port are not defined");
+		} catch (Exception e) {
+			JOptionPane
+				.showMessageDialog(null, "Error loading configuration values: \n" + e.toString(), "Configuration error", JOptionPane.ERROR_MESSAGE);
+			System.exit(1);
 			e.printStackTrace();
 		}
 
-		// Override configuration values with command line arguments
+		// Ask the user for their user name
-		if (args.length > 0) config.load(args);
-
-		if (!config.isInitialized()) {
-			logger.severe("Server or port are not defined. Exiting...");
-			JOptionPane.showMessageDialog(null, "Error loading configuration values.", "Configuration error", JOptionPane.ERROR_MESSAGE);
-			System.exit(1);
-		}
-
 		String userName = JOptionPane.showInputDialog("Please enter your username");
 		if (userName == null || userName.isEmpty()) {
 			logger.severe("User name is not set or empty. Exiting...");
 			System.exit(1);
 		}
-		Client	client	= new Client(config, userName);
+		
-		LocalDB	localDB	= new LocalDB(client.getSender());
+		// Initialize the local database
+		LocalDB localDB;
 		try {
-			localDB.initializeDBFile(config.getLocalDB());
+			localDB = new LocalDB(config.getLocalDB());
+		} catch (IOException e3) {
+			logger.log(Level.SEVERE, "Could not initialize local database", e3);
+			JOptionPane.showMessageDialog(null, "Could not initialize local database!\n" + e3.toString());
+			System.exit(1);
+			return;
+		}
+
+		// Acquire the client user (with ID) either from the server or from the local
+		// database, which triggers offline mode
+		Client client = new Client(config);
+		try {
+			// Try entering online mode first
+			client.onlineInit(userName);
+		} catch (Exception e1) {
+			logger.warning("Could not connect to server. Trying offline mode...");
+			try {
+				// Try entering offline mode
+				localDB.loadUsers();
+				User clientUser = localDB.getUsers().get(userName);
+				if(clientUser == null)
+					throw new EnvoyException("Could not enter offline mode: user name unknown");
+				client.setSender(clientUser);
+			} catch(Exception e2) {
+				JOptionPane.showMessageDialog(null, e1.toString(), "Client error", JOptionPane.ERROR_MESSAGE);
+				System.exit(1);
+				return;
+			}
+		}
+		
+		// Set client user in local database
+		localDB.setUser(client.getSender());
+		
+		// Initialize chats in local database
+		try {
+			localDB.initializeDBFile();
+			localDB.loadChats();
 		} catch (EnvoyException e) {
 			e.printStackTrace();
 			JOptionPane.showMessageDialog(null,
@@ -70,13 +104,23 @@ public class Startup {
 					"Local DB error",
 					JOptionPane.WARNING_MESSAGE);
 		}
-		Settings.getInstance().setUsername(userName);
+		
+		logger.info("Client user ID: " + client.getSender().getID());
+
+		// Save all users to the local database
+		if(client.isOnline())
+			localDB.setUsers(client.getUsers());
 		
 		EventQueue.invokeLater(() -> {
 			try {
 				ChatWindow chatWindow = new ChatWindow(client, localDB);
-				new StatusTrayIcon(chatWindow).show();
 				chatWindow.setVisible(true);
+
+				try {
+					new StatusTrayIcon(chatWindow).show();
+				} catch (EnvoyException e) {
+					logger.warning("The StatusTrayIcon is not supported on this platform!");
+				}
 			} catch (Exception e) {
 				e.printStackTrace();
 			}