Merge pull request #93 from informatik-ag-ngl/f/component_list

Component List

.classpath

@@ -28,11 +28,5 @@
 			<attribute name="maven.pomderived" value="true"/>
 		</attributes>
 	</classpathentry>
-	<classpathentry excluding="**" kind="src" output="target/test-classes" path="src/test/resources">
-		<attributes>
-			<attribute name="maven.pomderived" value="true"/>
-			<attribute name="test" value="true"/>
-		</attributes>
-	</classpathentry>
 	<classpathentry kind="output" path="target/classes"/>
 </classpath>

pom.xml

@@ -28,11 +28,16 @@
 		<dependency>
 			<groupId>com.github.informatik-ag-ngl</groupId>
 			<artifactId>envoy-common</artifactId>
-			<version>e5c67b8</version>
+			<version>develop-SNAPSHOT</version>
 		</dependency>
 	</dependencies>
 
 	<build>
 		<finalName>envoy-client</finalName>
+		<resources>
+			<resource>
+				<directory>src/main/resources</directory>
+			</resource>
+		</resources>
 	</build>
 </project>

src/main/java/envoy/client/Chat.java

@@ -2,9 +2,9 @@ package envoy.client;
 
 import java.io.Serializable;
 
-import javax.swing.DefaultListModel;
+import envoy.client.ui.list.ComponentListModel;
-
 import envoy.data.Message;
+import envoy.data.Message.MessageStatus;
 import envoy.data.User;
 
 /**
@@ -25,7 +25,7 @@ public class Chat implements Serializable {
 	private static final long serialVersionUID = -7751248474547242056L;
 
 	private User						recipient;
-	private DefaultListModel<Message>	model	= new DefaultListModel<>();
+	private ComponentListModel<Message>	model	= new ComponentListModel<>();
 
 	/**
 	 * Provides the list of messages that the recipient receives.<br>
@@ -37,22 +37,34 @@ public class Chat implements Serializable {
 	public Chat(User recipient) { this.recipient = recipient; }
 
 	/**
-	 * @return the recipient of a message
+	 * Appends a message to the bottom of this chat
+	 *
+	 * @param message the message to append
 	 * @since Envoy v0.1-alpha
 	 */
-	public User getRecipient() { return recipient; }
+	public void appendMessage(Message message) { model.add(message); }
 
 	/**
-	 * Adds the received message at the current Point in the current chat
+	 * Sets the status of all chat messages to {@code READ} starting from the bottom
+	 * and stopping once a read message is found.
 	 * 
-	 * @param message the message to add in said chat
+	 * @since Envoy v0.3-alpha
-	 * @since Envoy v0.1-alpha
 	 */
-	public void appendMessage(Message message) { model.addElement(message); }
+	public void read() {
+		for (int i = model.size() - 1; i >= 0; --i)
+			if (model.get(i).getStatus() == MessageStatus.READ) break;
+			else model.get(i).setStatus(MessageStatus.READ);
+	}
 
 	/**
 	 * @return all messages in the current chat
 	 * @since Envoy v0.1-alpha
 	 */
-	public DefaultListModel<Message> getModel() { return model; }
+	public ComponentListModel<Message> getModel() { return model; }
+
+	/**
+	 * @return the recipient of a message
+	 * @since Envoy v0.1-alpha
+	 */
+	public User getRecipient() { return recipient; }
 }

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

@@ -11,6 +11,7 @@ import javax.naming.TimeLimitExceededException;
 
 import envoy.client.util.EnvoyLog;
 import envoy.data.*;
+import envoy.event.IdGeneratorRequest;
 import envoy.util.SerializationUtils;
 
 /**
@@ -45,11 +46,13 @@ public class Client implements Closeable {
 	 * an exception is thrown.
 	 *
 	 * @param credentials the login credentials of the user
+	 * @param localDB     the local database used to persist the current
+	 *                    {@link IdGenerator}
 	 * @throws Exception if the online mode could not be entered or the request
 	 *                   failed for some other reason
 	 * @since Envoy v0.2-alpha
 	 */
-	public void onlineInit(LoginCredentials credentials) throws Exception {
+	public void onlineInit(LoginCredentials credentials, LocalDB localDB) throws Exception {
 		// Establish TCP connection
 		logger.info(String.format("Attempting connection to server %s:%d...", config.getServer(), config.getPort()));
 		socket = new Socket(config.getServer(), config.getPort());
@@ -84,6 +87,13 @@ public class Client implements Closeable {
 
 		// Register processors for message and status handling
 		receiver.registerProcessor(Message.class, new ReceivedMessageProcessor());
+		// TODO: Status handling
+
+		// Process message ID generation
+		receiver.registerProcessor(IdGenerator.class, localDB::setIdGenerator);
+
+		// Request a generator if none is present
+		if (!localDB.hasIdGenerator() || !localDB.getIdGenerator().hasNext()) requestIdGenerator();
 	}
 
 	/**
@@ -94,11 +104,21 @@ public class Client implements Closeable {
 	 * @since Envoy v0.3-alpha
 	 */
 	public void sendMessage(Message message) throws IOException {
-		checkOnline();
+		writeObject(message);
-		SerializationUtils.writeBytesWithLength(message, socket.getOutputStream());
 		message.nextStatus();
 	}
 
+	/**
+	 * Requests a new {@link IdGenerator} from the server.
+	 *
+	 * @throws IOException if the request does not reach the server
+	 * @since Envoy v0.3-alpha
+	 */
+	public void requestIdGenerator() throws IOException {
+		logger.info("Requesting new id generator...");
+		writeObject(new IdGeneratorRequest());
+	}
+
 	/**
 	 * @return a {@code Map<String, User>} of all users on the server with their
 	 *         user names as keys
@@ -114,6 +134,11 @@ public class Client implements Closeable {
 	@Override
 	public void close() throws IOException { if (online) socket.close(); }
 
+	private void writeObject(Object obj) throws IOException {
+		checkOnline();
+		SerializationUtils.writeBytesWithLength(obj, socket.getOutputStream());
+	}
+
 	private void checkOnline() { if (!online) throw new IllegalStateException("Client is not online"); }
 
 	/**

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

@@ -31,7 +31,6 @@ public class Config {
 		items.put("server", new ConfigItem<>("server", "s", (input) -> input, null));
 		items.put("port", new ConfigItem<>("port", "p", (input) -> Integer.parseInt(input), null));
 		items.put("localDB", new ConfigItem<>("localDB", "db", (input) -> new File(input), new File("localDB")));
-		items.put("syncTimeout", new ConfigItem<>("syncTimeout", "st", (input) -> Integer.parseInt(input), 1000));
 		items.put("homeDirectory",
 				new ConfigItem<>("homeDirectory", "h", (input) -> new File(input), new File(System.getProperty("user.home"), ".envoy")));
 		items.put("fileLevelBarrier", new ConfigItem<>("fileLevelBarrier", "fb", (input) -> Level.parse(input), Level.CONFIG));
@@ -112,7 +111,7 @@ public class Config {
 	 * @return the port at which the Envoy server is located on the host
 	 * @since Envoy v0.1-alpha
 	 */
-	public int getPort() { return (int) items.get("port").get(); }
+	public Integer getPort() { return (Integer) items.get("port").get(); }
 
 	/**
 	 * @return the local database specific to the client user
@@ -120,12 +119,6 @@ public class Config {
 	 */
 	public File getLocalDB() { return (File) items.get("localDB").get(); }
 
-	/**
-	 * @return the current time (milliseconds) that is waited between Syncs
-	 * @since Envoy v0.1-alpha
-	 */
-	public int getSyncTimeout() { return (int) items.get("syncTimeout").get(); }
-
 	/**
 	 * @return the directory in which all local files are saves
 	 * @since Envoy v0.2-alpha

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

@@ -4,10 +4,15 @@ import java.io.File;
 import java.io.IOException;
 import java.util.*;
 
+import envoy.data.IdGenerator;
 import envoy.data.User;
 import envoy.util.SerializationUtils;
 
 /**
+ * Stored information about the current {@link User} and their {@link Chat}s.
+ * For message ID generation a {@link IdGenerator} is stored as well.
+ * These object are persisted inside a folder of the local file system.<br>
+ * <br>
  * Project: <strong>envoy-client</strong><br>
  * File: <strong>LocalDB.java</strong><br>
  * Created: <strong>27.10.2019</strong><br>
@@ -18,10 +23,11 @@ import envoy.util.SerializationUtils;
  */
 public class LocalDB {
 
-	private File				localDBDir, localDBFile, usersFile;
+	private File				localDBDir, localDBFile, usersFile, idGeneratorFile;
 	private User				user;
 	private Map<String, User>	users	= new HashMap<>();
 	private List<Chat>			chats	= new ArrayList<>();
+	private IdGenerator			idGenerator;
 
 	/**
 	 * Constructs an empty local database. To serialize any chats to the file
@@ -38,6 +44,7 @@ public class LocalDB {
 		if (localDBDir.exists() && !localDBDir.isDirectory())
 			throw new IOException(String.format("LocalDBDir '%s' is not a directory!", localDBDir.getAbsolutePath()));
 		usersFile		= new File(localDBDir, "users.db");
+		idGeneratorFile	= new File(localDBDir, "id_generator.db");
 	}
 
 	/**
@@ -53,7 +60,8 @@ public class LocalDB {
 
 	/**
 	 * Stores all users to the local database. If the client user is specified, the
-	 * chats related to this user are stored as well.
+	 * chats related to this user are stored as well. The message id generator will
+	 * also be saved if present.
 	 *
 	 * @throws IOException if something went wrong during saving
 	 * @since Envoy v0.1-alpha
@@ -63,7 +71,10 @@ public class LocalDB {
 		SerializationUtils.write(usersFile, users);
 
 		// Save chats
-		SerializationUtils.write(localDBFile, chats);
+		if (user != null) SerializationUtils.write(localDBFile, chats);
+
+		// Save id generator
+		if (hasIdGenerator()) SerializationUtils.write(idGeneratorFile, idGenerator);
 	}
 
 	/**
@@ -84,6 +95,18 @@ public class LocalDB {
 	 */
 	public void loadChats() throws ClassNotFoundException, IOException { chats = SerializationUtils.read(localDBFile, ArrayList.class); }
 
+	/**
+	 * Loads the message ID generator that is stored in the local database. If the
+	 * file is not found, the exception is ignored.
+	 *
+	 * @since Envoy v0.3-alpha
+	 */
+	public void loadIdGenerator() {
+		try {
+			idGenerator = SerializationUtils.read(idGeneratorFile, IdGenerator.class);
+		} catch (ClassNotFoundException | IOException e) {}
+	}
+
 	/**
 	 * @return a {@code Map<String, User>} of all users stored locally with their
 	 *         user names as keys
@@ -119,4 +142,22 @@ public class LocalDB {
 	 * @since Envoy v0.2-alpha
 	 */
 	public void setUser(User user) { this.user = user; }
+
+	/**
+	 * @return the message ID generator
+	 * @since Envoy v0.3-alpha
+	 */
+	public IdGenerator getIdGenerator() { return idGenerator; }
+
+	/**
+	 * @param idGenerator the message ID generator to set
+	 * @since Envoy v0.3-alpha
+	 */
+	public void setIdGenerator(IdGenerator idGenerator) { this.idGenerator = idGenerator; }
+
+	/**
+	 * @return {@code true} if an {@link IdGenerator} is present
+	 * @since Envoy v0.3-alpha
+	 */
+	public boolean hasIdGenerator() { return idGenerator != null; }
 }

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

@@ -135,7 +135,7 @@ public class Settings {
 	 *         {@code Control} key.
 	 * @since Envoy v0.2-alpha
 	 */
-	public boolean isEnterToSend() { return (boolean) items.get("enterToSend").get(); }
+	public Boolean isEnterToSend() { return (Boolean) items.get("enterToSend").get(); }
 
 	/**
 	 * Changes the keystrokes performed by the user to send a message.
@@ -152,7 +152,7 @@ public class Settings {
 	 * @return the current on close mode.
 	 * @since Envoy v0.3-alpha
 	 */
-	public boolean getCurrentOnCloseMode() { return (boolean) items.get("onCloseMode").get(); }
+	public Boolean getCurrentOnCloseMode() { return (Boolean) items.get("onCloseMode").get(); }
 
 	/**
 	 * Sets the current on close mode.

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

@@ -10,7 +10,9 @@ import javax.swing.*;
 import javax.swing.border.EmptyBorder;
 
 import envoy.client.*;
+import envoy.client.event.MessageCreationEvent;
 import envoy.client.event.ThemeChangeEvent;
+import envoy.client.ui.list.ComponentList;
 import envoy.client.ui.settings.SettingsScreen;
 import envoy.client.util.EnvoyLog;
 import envoy.data.Message;
@@ -30,8 +32,6 @@ import envoy.event.EventBus;
  */
 public class ChatWindow extends JFrame {
 
-	private static final long serialVersionUID = 6865098428255463649L;
-
 	// User specific objects
 	private Client	client;
 	private LocalDB	localDB;
@@ -41,16 +41,20 @@ public class ChatWindow extends JFrame {
 	private PrimaryTextArea			messageEnterTextArea	= new PrimaryTextArea(space);
 	private JList<User>				userList				= new JList<>();
 	private Chat					currentChat;
-	private JList<Message>		messageList				= new JList<>();
+	private ComponentList<Message>	messageList				= new ComponentList<>(new MessageListRenderer());
 	private PrimaryScrollPane		scrollPane				= new PrimaryScrollPane();
 	private JTextPane				textPane				= new JTextPane();
 	private PrimaryButton			postButton				= new PrimaryButton("Post");
 	private PrimaryButton			settingsButton			= new PrimaryButton("Settings");
 
-	private static int space = 4;
-
 	private static final Logger logger = EnvoyLog.getLogger(ChatWindow.class.getSimpleName());
 
+	// GUI component spacing
+	private final static int	space	= 4;
+	private static final Insets	insets	= new Insets(space, space, space, space);
+
+	private static final long serialVersionUID = 6865098428255463649L;
+
 	/**
 	 * Initializes a {@link JFrame} with UI elements used to send and read messages
 	 * to different users.
@@ -73,14 +77,11 @@ public class ChatWindow extends JFrame {
 		gbl_contentPane.rowWeights		= new double[] { 0.05, 1.0, 0.07 };
 		contentPane.setLayout(gbl_contentPane);
 
-		messageList.setCellRenderer(new MessageListRenderer());
+		// TODO: messageList.setFocusTraversalKeysEnabled(false);
-		messageList.setFocusTraversalKeysEnabled(false);
+		// messageList.setComponentOrientation(ComponentOrientation.LEFT_TO_RIGHT);
-		messageList.setComponentOrientation(ComponentOrientation.LEFT_TO_RIGHT);
 
-		DefaultListModel<Message> messageListModel = new DefaultListModel<>();
+		// messageList.setFont(new Font("Arial", Font.PLAIN, 17));
-		messageList.setModel(messageListModel);
+		// messageList.setFixedCellHeight(60);
-		messageList.setFont(new Font("Arial", Font.PLAIN, 17));
-		messageList.setFixedCellHeight(60);
 		messageList.setBorder(new EmptyBorder(space, space, space, space));
 
 		scrollPane.setViewportView(messageList);
@@ -91,7 +92,7 @@ public class ChatWindow extends JFrame {
 		gbc_scrollPane.gridx		= 1;
 		gbc_scrollPane.gridy		= 1;
 
-		gbc_scrollPane.insets = new Insets(space, space, space, space);
+		gbc_scrollPane.insets = insets;
 		contentPane.add(scrollPane, gbc_scrollPane);
 
 		// Message enter field
@@ -100,8 +101,8 @@ public class ChatWindow extends JFrame {
 			@Override
 			public void keyReleased(KeyEvent e) {
 				if (e.getKeyCode() == KeyEvent.VK_ENTER
-						&& ((Settings.getInstance().isEnterToSend() && e.getModifiersEx() == 0) || (e.getModifiersEx() == KeyEvent.CTRL_DOWN_MASK)))
+						&& (Settings.getInstance().isEnterToSend() && e.getModifiersEx() == 0 || e.getModifiersEx() == KeyEvent.CTRL_DOWN_MASK))
-					postMessage(messageList);
+					postMessage();
 			}
 		});
 
@@ -110,7 +111,7 @@ public class ChatWindow extends JFrame {
 		gbc_messageEnterTextfield.gridx	= 1;
 		gbc_messageEnterTextfield.gridy	= 2;
 
-		gbc_messageEnterTextfield.insets = new Insets(space, space, space, space);
+		gbc_messageEnterTextfield.insets = insets;
 
 		contentPane.add(messageEnterTextArea, gbc_messageEnterTextfield);
 
@@ -121,9 +122,9 @@ public class ChatWindow extends JFrame {
 		gbc_moveSelectionPostButton.gridx	= 2;
 		gbc_moveSelectionPostButton.gridy	= 2;
 
-		gbc_moveSelectionPostButton.insets = new Insets(space, space, space, space);
+		gbc_moveSelectionPostButton.insets = insets;
 
-		postButton.addActionListener((evt) -> { postMessage(messageList); });
+		postButton.addActionListener((evt) -> { postMessage(); });
 		contentPane.add(postButton, gbc_moveSelectionPostButton);
 
 		// Settings Button
@@ -133,7 +134,7 @@ public class ChatWindow extends JFrame {
 		gbc_moveSelectionSettingsButton.gridx	= 2;
 		gbc_moveSelectionSettingsButton.gridy	= 0;
 
-		gbc_moveSelectionSettingsButton.insets = new Insets(space, space, space, space);
+		gbc_moveSelectionSettingsButton.insets = insets;
 
 		settingsButton.addActionListener((evt) -> {
 			try {
@@ -154,7 +155,7 @@ public class ChatWindow extends JFrame {
 		gbc_partnerName.gridx	= 1;
 		gbc_partnerName.gridy	= 0;
 
-		gbc_partnerName.insets = new Insets(space, space, space, space);
+		gbc_partnerName.insets = insets;
 		contentPane.add(textPane, gbc_partnerName);
 
 		userList.setCellRenderer(new UserListRenderer());
@@ -165,17 +166,22 @@ public class ChatWindow extends JFrame {
 				final JList<User>	selectedUserList	= (JList<User>) listSelectionEvent.getSource();
 				final User			user				= selectedUserList.getSelectedValue();
 
+				// Select current chat
 				currentChat = localDB.getChats().stream().filter(chat -> chat.getRecipient().getId() == user.getId()).findFirst().get();
 
-				// Set all unread messages in the chat to read
+				// Read current Chat
-				readCurrentChat();
+				currentChat.read();
 
+				// Set recipient in client and chat title
 				client.setRecipient(user);
 				textPane.setText(currentChat.getRecipient().getName());
 
+				// Update model and scroll down
 				messageList.setModel(currentChat.getModel());
 				scrollPane.setChatOpened(true);
-				contentPane.revalidate();
+
+				revalidate();
+				repaint();
 			}
 		});
 
@@ -187,20 +193,29 @@ public class ChatWindow extends JFrame {
 		gbc_userList.gridx	= 0;
 		gbc_userList.gridy	= 1;
 		gbc_userList.anchor	= GridBagConstraints.PAGE_START;
-		gbc_userList.insets	= new Insets(space, space, space, space);
+		gbc_userList.insets	= insets;
 
 		applyTheme(Settings.getInstance().getThemes().get(Settings.getInstance().getCurrentTheme()));
 
 		contentPane.add(userList, gbc_userList);
 		contentPane.revalidate();
 
+		// Listen to theme changes
 		EventBus.getInstance().register(ThemeChangeEvent.class, (evt) -> applyTheme((Theme) evt.get()));
 
-		contentPane.revalidate();
+		// Listen to received messages
+		EventBus.getInstance().register(MessageCreationEvent.class, (evt) -> {
+			Message message = ((MessageCreationEvent) evt).get();
+			localDB.getChats().stream().filter(c -> c.getRecipient().getId() == message.getSenderId()).findFirst().get().appendMessage(message);
+			revalidate();
+			repaint();
+		});
+
+		revalidate();
 	}
 
 	/**
-	 * Used to immediately reload the ChatWindow when settings were changed.
+	 * Used to immediately reload the {@link ChatWindow} when settings were changed.
 	 *
 	 * @param theme the theme to change colors into
 	 * @since Envoy v0.2-alpha
@@ -210,8 +225,8 @@ public class ChatWindow extends JFrame {
 		contentPane.setBackground(theme.getBackgroundColor());
 		contentPane.setForeground(theme.getUserNameColor());
 		// messageList
-		messageList.setSelectionForeground(theme.getUserNameColor());
+		// messageList.setSelectionForeground(theme.getUserNameColor());
-		messageList.setSelectionBackground(theme.getSelectionColor());
+		// messageList.setSelectionBackground(theme.getSelectionColor());
 		messageList.setForeground(theme.getMessageColorChat());
 		messageList.setBackground(theme.getCellColor());
 		// scrollPane
@@ -238,7 +253,7 @@ public class ChatWindow extends JFrame {
 		userList.setBackground(theme.getCellColor());
 	}
 
-	private void postMessage(JList<Message> messageList) {
+	private void postMessage() {
 		if (!client.hasRecipient()) {
 			JOptionPane.showMessageDialog(this, "Please select a recipient!", "Cannot send message", JOptionPane.INFORMATION_MESSAGE);
 			return;
@@ -247,24 +262,32 @@ public class ChatWindow extends JFrame {
 		if (!messageEnterTextArea.getText().isEmpty()) try {
 
 			// Create message
-			final Message message = new MessageBuilder(localDB.getUser().getId(), currentChat.getRecipient().getId())
+			final Message message = new MessageBuilder(localDB.getUser().getId(), currentChat.getRecipient().getId(), localDB.getIdGenerator())
 				.setText(messageEnterTextArea.getText())
 				.build();
 
 			// Send message
+			// TODO: Store offline messages
 			client.sendMessage(message);
 
 			// Add message to LocalDB and update UI
 			currentChat.appendMessage(message);
-			messageList.setModel(currentChat.getModel());
+			// messageList.setModel(currentChat.getModel());
 
 			// Clear text field
 			messageEnterTextArea.setText("");
-			contentPane.revalidate();
+
+			// Update UI
+			revalidate();
+			repaint();
+
+			// Request a new id generator if all ids were used
+			if (!localDB.getIdGenerator().hasNext()) client.requestIdGenerator();
+
 		} catch (Exception e) {
 			JOptionPane.showMessageDialog(this,
-					"An exception occured while sending a message. See the log for more details.",
+					"Error sending message:\n" + e.toString(),
-					"Exception occured",
+					"Message sending error",
 					JOptionPane.ERROR_MESSAGE);
 			e.printStackTrace();
 		}
@@ -291,64 +314,13 @@ public class ChatWindow extends JFrame {
 	}
 
 	/**
-	 * Updates the data model and the UI repeatedly after a certain amount of
+	 * Sets the {@link Client} used by this {@link ChatWindow}.
-	 * time.
-	 *
-	 * @param timeout the amount of time that passes between two requests sent to
-	 *                the server
-	 * @since Envoy v0.1-alpha
-	 */
-	private void startSyncThread(int timeout) {
-		new Timer(timeout, (evt) -> {
-			new Thread(() -> {
-
-				// Synchronize
-				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);
-				}
-
-				// TODO: Process unread messages
-				// localDB.addUnreadMessagesToLocalDB();
-				// localDB.clearUnreadMessagesSync();
-
-				// Mark unread messages as read when they are in the current chat
-				readCurrentChat();
-
-				// Update UI
-				SwingUtilities.invokeLater(() -> { updateUserStates(); contentPane.revalidate(); contentPane.repaint(); });
-			}).start();
-		}).start();
-	}
-
-	private void updateUserStates() {
-		for (int i = 0; i < userList.getModel().getSize(); i++)
-			for (int j = 0; j < localDB.getChats().size(); j++)
-				if (userList.getModel().getElementAt(i).getId() == localDB.getChats().get(j).getRecipient().getId())
-					userList.getModel().getElementAt(i).setStatus(localDB.getChats().get(j).getRecipient().getStatus());
-	}
-
-	/**
-	 * Marks messages in the current chat as {@code READ}.
-	 */
-	private void readCurrentChat() {
-		if (currentChat != null) {
-			// TODO: localDB.setMessagesToRead(currentChat);
-		}
-	}
-
-	/**
-	 * Sets the {@link Client} used by this {@link ChatWindow}. If the client is
-	 * online, the sync thread is started.
 	 *
 	 * @param client the {@link Client} used to send and receive messages
 	 * @since Envoy v0.2-alpha
 	 */
 	public void setClient(Client client) {
 		this.client = client;
-		if (client.isOnline() && localDB != null) startSyncThread(Config.getInstance().getSyncTimeout());
 	}
 
 	/**
@@ -361,6 +333,5 @@ public class ChatWindow extends JFrame {
 	public void setLocalDB(LocalDB localDB) {
 		this.localDB = localDB;
 		loadUsersAndChats();
-		if (client != null && client.isOnline()) startSyncThread(Config.getInstance().getSyncTimeout());
 	}
 }

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

@@ -1,13 +1,13 @@
 package envoy.client.ui;
 
-import java.awt.Component;
+import java.awt.Dimension;
 import java.text.SimpleDateFormat;
 
-import javax.swing.JLabel;
+import javax.swing.*;
-import javax.swing.JList;
-import javax.swing.ListCellRenderer;
 
 import envoy.client.Settings;
+import envoy.client.ui.list.ComponentList;
+import envoy.client.ui.list.ComponentListCellRenderer;
 import envoy.data.Message;
 
 /**
@@ -21,22 +21,22 @@ import envoy.data.Message;
  * @author Maximilian Käfer
  * @since Envoy v0.1-alpha
  */
-public class MessageListRenderer extends JLabel implements ListCellRenderer<Message> {
+public class MessageListRenderer implements ComponentListCellRenderer<Message> {
-
-	private static final long serialVersionUID = 5164417379767181198L;
 
 	@Override
-	public Component getListCellRendererComponent(JList<? extends Message> list, Message value, int index, boolean isSelected, boolean cellHasFocus) {
+	public JComponent getListCellComponent(ComponentList<? extends Message> list, Message value, boolean isSelected) {
+		final JPanel panel = new JPanel();
 		if (isSelected) {
-			setBackground(list.getSelectionBackground());
+			panel.setBackground(Color.DARK_GRAY);
-			setForeground(list.getSelectionForeground());
+			panel.setForeground(Color.RED);
+			// TODO: Selection
+			// setBackground(list.getSelectionBackground());
+			// setForeground(list.getSelectionForeground());
 		} else {
-			setBackground(list.getBackground());
+			panel.setBackground(list.getBackground());
-			setForeground(list.getForeground());
+			panel.setForeground(list.getForeground());
 		}
 
-		setOpaque(true);
-
 		// TODO: Handle message attachments
 
 		final String	text	= value.getText();
@@ -49,12 +49,22 @@ public class MessageListRenderer extends JLabel implements ListCellRenderer<Mess
 		// Getting the DateColor in the Chat of the current theme
 		String dateColor = Settings.getInstance().getThemes().get(Settings.getInstance().getCurrentTheme()).getDateColorChat().toHex();
 
-		setText(String.format("<html><p style=\"color:%s\"><b><small>%s</b></small><br><p style=\"color:%s\">%s :%s</html>",
+		panel.add(new JLabel(String.format("<html><p style=\"color:%s\"><b><small>%s</b></small><br><p style=\"color:%s\">%s :%s</html>",
 				dateColor,
 				date,
 				textColor,
 				text,
-				state));
+				state)));
-		return this;
+
+		// Define some space to the messages below
+		panel.setBorder(BorderFactory.createCompoundBorder(BorderFactory.createEmptyBorder(0, 0, 15, 0), BorderFactory.createEtchedBorder()));
+
+		// Define a maximum height of 50px
+		Dimension size = new Dimension(list.getWidth() - 25, 50);
+		panel.setMaximumSize(size);
+		panel.setMinimumSize(size);
+		panel.setPreferredSize(size);
+
+		return panel;
 	}
 }

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

@@ -62,7 +62,7 @@ public class Startup {
 			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);
+				.showMessageDialog(null, "Error loading configuration values:\n" + e.toString(), "Configuration error", JOptionPane.ERROR_MESSAGE);
 			System.exit(1);
 			e.printStackTrace();
 		}
@@ -97,7 +97,8 @@ public class Startup {
 		Client client = new Client();
 		try {
 			// Try entering online mode first
-			client.onlineInit(credentials);
+			localDB.loadIdGenerator();
+			client.onlineInit(credentials, localDB);
 		} catch (Exception e1) {
 			logger.warning("Could not connect to server. Trying offline mode...");
 			e1.printStackTrace();
@@ -152,7 +153,7 @@ public class Startup {
 						.getItems()
 						.get("onCloseMode")
 						.setChangeHandler((onCloseMode) -> chatWindow
-							.setDefaultCloseOperation((boolean) onCloseMode ? JFrame.HIDE_ON_CLOSE : JFrame.EXIT_ON_CLOSE));
+							.setDefaultCloseOperation((Boolean) onCloseMode ? JFrame.HIDE_ON_CLOSE : JFrame.EXIT_ON_CLOSE));
 				} catch (EnvoyException e) {
 					logger.warning("The StatusTrayIcon is not supported on this platform!");
 				}

src/main/java/envoy/client/ui/list/ComponentList.java

@@ -0,0 +1,91 @@
+package envoy.client.ui.list;
+
+import javax.swing.BoxLayout;
+import javax.swing.JPanel;
+
+/**
+ * Provides a vertical list layout of components provided in a
+ * {@link ComponentListModel}. Similar to {@link javax.swing.JList} but capable
+ * of rendering {@link JPanel}s.<br>
+ * <br>
+ * Project: <strong>envoy-client</strong><br>
+ * File: <strong>ComponentList.java</strong><br>
+ * Created: <strong>25.01.2020</strong><br>
+ *
+ * @param <E> the type of object displayed in this list
+ * @author Kai S. K. Engelbart
+ * @since Envoy v0.3-alpha
+ */
+public class ComponentList<E> extends JPanel {
+
+	private ComponentListModel<E>			model;
+	private ComponentListCellRenderer<E>	renderer;
+
+	private static final long serialVersionUID = 1759644503942876737L;
+
+	/**
+	 * Creates an instance of {@link ComponentList}.
+	 *
+	 * @param renderer the list cell renderer used to display elements provided by
+	 *                 the {@link ComponentListModel}
+	 * @since Envoy v0.3-alpha
+	 */
+	public ComponentList(ComponentListCellRenderer<E> renderer) {
+		setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
+		this.renderer = renderer;
+	}
+
+	/**
+	 * Creates an instance of {@link ComponentList}.
+	 *
+	 * @param model    the list model providing the list elements to render
+	 * @param renderer the list cell renderer used to display elements provided by
+	 *                 the {@link ComponentListModel}
+	 * @since Envoy v0.3-alpha
+	 */
+	public ComponentList(ComponentListModel<E> model, ComponentListCellRenderer<E> renderer) {
+		this(renderer);
+		this.model = model;
+		setModel(model);
+	}
+
+	/**
+	 * Sets the list model providing the list elements to render
+	 *
+	 * @param model the list model to set
+	 * @since Envoy v0.3-alpha
+	 */
+	public void setModel(ComponentListModel<E> model) {
+		// Remove old model
+		if (this.model != null)
+			this.model.setComponentList(null);
+
+		// Synchronize with new model
+		this.model = model;
+		this.model.setComponentList(this);
+		synchronizeModel();
+	}
+
+	/**
+	 * Adds an object to the list by rendering it with the current
+	 * {@link ComponentListCellRenderer}.
+	 *
+	 * @param elem the element to add
+	 * @since Envoy v0.3-alpha
+	 */
+	void add(E elem) {
+		add(renderer.getListCellComponent(this, elem, false));
+	}
+
+	/**
+	 * Removes all child components and then adds all components representing the
+	 * elements of the {@link ComponentListModel}.
+	 *
+	 * @since Envoy v0.3-alpha
+	 */
+	void synchronizeModel() {
+		removeAll();
+		if (model != null) for (E elem : model)
+			add(elem);
+	}
+}

src/main/java/envoy/client/ui/list/ComponentListCellRenderer.java

@@ -0,0 +1,30 @@
+package envoy.client.ui.list;
+
+import javax.swing.JComponent;
+
+/**
+ * Allows a {@link ComponentList} convert its elements into Swing components
+ * that can be rendered.<br>
+ * <br>
+ * Project: <strong>envoy-client</strong><br>
+ * File: <strong>ComponentListCellRenderer.java</strong><br>
+ * Created: <strong>25.01.2020</strong><br>
+ *
+ * @param <E> the type of object displayed in this list
+ * @author Kai S. K. Engelbart
+ * @since Envoy v0.3-alpha
+ */
+public interface ComponentListCellRenderer<E> {
+
+	/**
+	 * Provides a Swing component representing a list element.
+	 *
+	 * @param list       the list in which the component will be displayed
+	 * @param value      the list element that will be converted
+	 * @param isSelected {@code true} if the user has selected the list cell in
+	 *                   which the list element is rendered
+	 * @return the component representing the list element
+	 * @since Envoy v0.3-alpha
+	 */
+	JComponent getListCellComponent(ComponentList<? extends E> list, E value, boolean isSelected);
+}

src/main/java/envoy/client/ui/list/ComponentListModel.java

@@ -0,0 +1,111 @@
+package envoy.client.ui.list;
+
+import java.io.Serializable;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+/**
+ * Stores objects that will be displayed in a {@link ComponentList}.<br>
+ * <br>
+ * Project: <strong>envoy-client</strong><br>
+ * File: <strong>ComponentListModel.java</strong><br>
+ * Created: <strong>25.01.2020</strong><br>
+ *
+ * @param <E> the type of object displayed in this list
+ * @author Kai S. K. Engelbart
+ * @since Envoy v0.3-alpha
+ */
+public final class ComponentListModel<E> implements Iterable<E>, Serializable {
+
+	private List<E>						elements	= new ArrayList<>();
+	transient private ComponentList<E>	componentList;
+
+	private static final long serialVersionUID = 4815005915255497331L;
+
+	/**
+	 * Adds an element to this model and notifies the associated
+	 * {@link ComponentList} to add the corresponding component.
+	 *
+	 * @param e the element to add
+	 * @return {@code true}
+	 * @see java.util.List#add(java.lang.Object)
+	 * @since Envoy v0.3-alpha
+	 */
+	public boolean add(E e) {
+		if (componentList != null) componentList.add(e);
+		return elements.add(e);
+	}
+
+	/**
+	 * Removes all elements from this model and clears the associated
+	 * {@link ComponentList}.
+	 *
+	 * @see java.util.List#clear()
+	 * @since Envoy v0.3-alpha
+	 */
+	public void clear() {
+		elements.clear();
+		if (componentList != null) componentList.removeAll();
+	}
+
+	/**
+	 * @param index the index to retrieve the element from
+	 * @return the element located at the index
+	 * @see java.util.List#get(int)
+	 * @since Envoy v0.3-alpha
+	 */
+	public E get(int index) { return elements.get(index); }
+
+	/**
+	 * Removes the element at a specific index from this model and the corresponding
+	 * component from the {@link ComponentList}.
+	 *
+	 * @param index the index of the element to remove
+	 * @return the removed element
+	 * @see java.util.List#remove(int)
+	 * @since Envoy v0.3-alpha
+	 */
+	public E remove(int index) {
+		if (componentList != null) componentList.remove(index);
+		return elements.remove(index);
+	}
+
+	/**
+	 * @return the amount of elements in this list model
+	 * @see java.util.List#size()
+	 * @since Envoy v0.3-alpha
+	 */
+	public int size() { return elements.size(); }
+
+	/**
+	 * @return an iterator over the elements of this list model
+	 * @see java.util.List#iterator()
+	 * @since Envoy v0.3-alpha
+	 */
+	@Override
+	public Iterator<E> iterator() {
+		return new Iterator<E>() {
+
+			Iterator<E> iter = elements.iterator();
+
+			@Override
+			public boolean hasNext() { return iter.hasNext(); }
+
+			@Override
+			public E next() { return iter.next(); }
+		};
+	}
+
+	/**
+	 * Sets the component list displaying the elements of this model and triggers a
+	 * synchronization.
+	 *
+	 * @param componentList the component list to set
+	 * @since Envoy v0.3-alpha
+	 */
+	void setComponentList(ComponentList<E> componentList) {
+		this.componentList = componentList;
+		if (componentList != null) componentList.synchronizeModel();
+	}
+}