Added offline mode to Client

+ Saving the user ID in Settings
+ Loading the user ID from Settings in Client if the server can't be
reached

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

@@ -10,6 +10,7 @@ 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 +30,18 @@ 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());
 
-	public Client(Config config, String username) {
+	public Client(Config config, String userName) throws EnvoyException {
 		this.config	= config;
-		sender		= getUser(username);
-
-		logger.info("ID: " + sender.getID());
+		sender		= getUser(userName);
+		
+		// Update the user ID in the cache
+		Settings.getInstance().setUserID(sender.getID());
+		
+		logger.info("Client user ID: " + sender.getID());
 	}
 
 	private <T, R> R post(String uri, T body, Class<R> responseBodyClass) {
@@ -48,7 +53,6 @@ public class Client {
 		client.close();
 
 		return responseBody;
-
 	}
 
 	/**
@@ -63,9 +67,7 @@ public class Client {
 		user.setID(-1);
 		sendSync.getUsers().add(user);
 
-		Sync returnSendSync = post(
-				String
-					.format("%s:%d/envoy-server/rest/sync/syncData?userId=%d", config.getServer(), config.getPort(), 0),
+		Sync returnSendSync = post(String.format("%s:%d/envoy-server/rest/sync/syncData?userId=%d", config.getServer(), config.getPort(), 0),
 				sendSync,
 				Sync.class);
 		return returnSendSync;
@@ -77,29 +79,33 @@ 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(
-				String
-					.format("%s:%d/envoy-server/rest/sync/syncData?userId=%d", config.getServer(), config.getPort(), 0),
-				senderSync,
-				Sync.class);
+		try {
+			Sync sync = post(String.format("%s:%d/envoy-server/rest/sync/syncData?userId=%d", config.getServer(), config.getPort(), 0),
+					senderSync,
+					Sync.class);
 
-		User returnSender = objectFactory.createUser();
-
-		if (returnSenderSync.getUsers().size() == 1) {
-			returnSender = returnSenderSync.getUsers().get(0);
-		} else {
-			logger.warning("ERROR exiting...");
+			// Expecting a single user with an ID
+			if (sync.getUsers().size() == 1) {
+				online = true;
+				return sync.getUsers().get(0);
+			} else throw new EnvoyException("Unexpected response from Envoy Server");
+		} catch (Exception e) {
+			logger.warning("Could not connect to server, trying offline mode.");
+			if (Settings.getInstance().getUserID() != -1) {
+				user.setID(Settings.getInstance().getUserID());
+				return user;
+			} else throw new EnvoyException("Could not enter offline mode.");
 		}
-
-		return returnSender;
 	}
 
 	/**
@@ -134,7 +140,8 @@ 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
 	 * @since Envoy v0.1-alpha
 	 */
@@ -151,10 +158,7 @@ public class Client {
 		}
 
 		// Send sync
-		return post(String
-			.format("%s:%d/envoy-server/rest/sync/syncData?userId=%d", config.getServer(), config.getPort(), userId),
-				sync,
-				Sync.class);
+		return post(String.format("%s:%d/envoy-server/rest/sync/syncData?userId=%d", config.getServer(), config.getPort(), userId), sync, Sync.class);
 	}
 
 	/**
@@ -182,4 +186,9 @@ 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
+	 */
+	public boolean isOnline() { return online; }
 }

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

@@ -27,6 +27,7 @@ public class Settings {
 
 	// Actual settings accessible by the rest of the application
 	private String				username;
+	private long				userID;
 	private String				email;
 	private boolean				enterToSend	= true;
 	private Map<String, Theme>	themes;
@@ -66,6 +67,7 @@ public class Settings {
 	@SuppressWarnings("unchecked")
 	private void load() {
 		setUsername(prefs.get("username", ""));
+		setUserID(prefs.getLong("userID", -1));
 		setEmail(prefs.get("email", ""));
 		setEnterToSend(prefs.getBoolean("enterToSend", true));
 		setCurrentTheme(prefs.get("theme", "dark"));
@@ -73,9 +75,9 @@ public class Settings {
 		// Load themes from theme file
 		try (ObjectInputStream in = new ObjectInputStream(new FileInputStream(themeFile))) {
 			Object obj = in.readObject();
-			if(obj instanceof HashMap) themes = (Map<String, Theme>) obj;
+			if (obj instanceof HashMap) themes = (Map<String, Theme>) obj;
 		} catch (IOException | ClassNotFoundException e) {
-			themes = new HashMap<>();
+			themes			= new HashMap<>();
 			currentTheme	= "dark";
 			e.printStackTrace();
 		}
@@ -90,20 +92,21 @@ 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{
+	public void save() throws IOException {
 		prefs.put("username", getUsername());
+		prefs.putLong("userID", getUserID());
 		prefs.put("email", getEmail());
 		prefs.put("theme", currentTheme);
 		prefs.putBoolean("enterToSend", isEnterToSend());
-		
+
 		// Save themes to theme file
 		themeFile.createNewFile();
-		try(ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(themeFile))) {
+		try (ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(themeFile))) {
 			out.writeObject(themes);
 		}
 	}
@@ -145,6 +148,16 @@ public class Settings {
 	 */
 	public void setUsername(String username) { this.username = username; }
 
+	/**
+	 * @return the userID
+	 */
+	public long getUserID() { return userID; }
+
+	/**
+	 * @param userID the userID to set
+	 */
+	public void setUserID(long userID) { this.userID = userID; }
+
 	/**
 	 * @return the email associated with that user.
 	 * @since Envoy v0.2-alpha

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

@@ -16,7 +16,7 @@ import envoy.exception.EnvoyException;
 
 /**
  * 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>
@@ -48,19 +48,34 @@ public class Startup {
 		// 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()) {
 			logger.severe("Server or port are not defined. Exiting...");
 			JOptionPane.showMessageDialog(null, "Error loading configuration values.", "Configuration error", JOptionPane.ERROR_MESSAGE);
 			System.exit(1);
 		}
 
+		// Ask the user for their user name
 		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());
+
+		// Acquire the client user (with ID) either from the server or from the local
+		// cache (Preferences), which triggers offline mode
+		Client client;
+		try {
+			client = new Client(config, userName);
+		} catch (Exception e1) {
+			logger.log(Level.SEVERE, "Failed to acquire client user ID", e1);
+			JOptionPane.showMessageDialog(null, e1.toString(), "Client error", JOptionPane.ERROR_MESSAGE);
+			System.exit(1);
+			return;
+		}
+
+		// Load the local database
+		LocalDB localDB = new LocalDB(client.getSender());
 		try {
 			localDB.initializeDBFile(config.getLocalDB());
 		} catch (EnvoyException e) {