-- DataBase Schema Untuk Contoh MenuLogin
 
CREATE DATABASE `menulogin`;
 
USE `menulogin`;
 
--
-- Table structure for table `T_USER`
--
DROP TABLE IF EXISTS `T_USER`;
CREATE TABLE `T_USER` (
  `id` int AUTO_INCREMENT NOT NULL,
  `username` varchar(255) DEFAULT NULL,
  `password` varchar(255) DEFAULT NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
 
--
-- Dumping data for table `T_USER`
--
INSERT INTO `T_USER` (`username`,`password`) VALUES 
('martin', 'menulogin'), ('ahmad','ganteng'),('slackware','linux');

public class UserApp {
    private Integer id;
    private String userName;
    private String password;
 
    // Generate Getter n Setter
}

public interface LoginService {
    /** Method ini akan mengecek apakah <code>username</code> dengan <code>password</code>
     * ada atau tidak di database
     * @param username user yang ingin di cek di database
     * @param password password untuk user
     * @return UserApp null jika tidak ditemukan
     */
    public UserApp login(String username, String password);
}

public class LoginServiceImpl implements LoginService {
 
    private Connection connection;
    private PreparedStatement findUserByUserAndPassword;
    private final String QRY_LOGIN = "select * from T_USER where" +
            " T_USER.username = ? and T_USER.password = ?";
 
    public LoginServiceImpl(Connection connection) {
        try {
            this.connection = connection;
            findUserByUserAndPassword = this.connection.prepareStatement(QRY_LOGIN);
        } catch (SQLException ex) {
            Logger.getLogger(LoginServiceImpl.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
 
    public UserApp login(String username, String password) {
        try {
            /* Lakukan pencarian berdasarkan username dan password */
            findUserByUserAndPassword.setString(1, username);
            findUserByUserAndPassword.setString(2, password);
 
            /* Ambil resultset-nya */
            ResultSet rs = findUserByUserAndPassword.executeQuery();
            while (rs.next()) {
                UserApp userApp = new UserApp();
                userApp.setId(rs.getInt("id"));
                userApp.setUserName(rs.getString("username"));
                userApp.setPassword(rs.getString("password"));
 
                return userApp;
            }
        } catch (SQLException ex) {
            Logger.getLogger(LoginServiceImpl.class.getName()).log(Level.SEVERE, null, ex);
        }
 
        return null;
    }
}

public class LoginDialog extends javax.swing.JDialog {
 
    private boolean notLogin = true;
    private GroupLayout gl;
 
    /** Creates new form LoginDialog */
    public LoginDialog(java.awt.Frame parent, boolean modal) {
        super(parent, modal);
        initComponents();
 
        /* Mendeteksi penekanan icon close, jika di close keluar dari aplikasi */
        addWindowListener(new java.awt.event.WindowAdapter() {
 
            @Override
            public void windowClosing(java.awt.event.WindowEvent e) {
                System.exit(0);
            }
        });
 
        jProgressBar1.setVisible(false);
 
        /* Membuat space progress bar tidak di *wrap* oleh button */
        gl = (GroupLayout) getContentPane().getLayout();
        gl.setHonorsVisibility(jProgressBar1, false);
 
        /* Beri fokus ke txtUsername ketika dialog tampil */
        txtUserName.requestFocusInWindow();
 
        /* Posisikan dialog seakan-akan berada di tengah-2x layar */
        setLocationRelativeTo(null);
    }
 
    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc=" Generated Code ">                          
    private void initComponents() { 
         ....
    }
    // </editor-fold>                        
 
    public boolean showDialog() {
        setVisible(true);
        return notLogin;
    }
 
    // Variables declaration - do not modify  
    ...                   
    // End of variables declaration                   
}

public class Main {
 
    private static MainForm mainForm;
    private static LoginService loginService;
 
    public static MainForm getMainForm() {
        return mainForm;
    }
 
    public static LoginService getLoginService() {
        return loginService;
    }
 
    /** Method ini akan menginisialisassi Form Utama kemudian akan melakukan
     * proses <code>loop</code> untuk menampilkan login dialog sampai nilai
     * notLogin = FALSE baru menampilkan Menu Utama */
    public static void initLogin() {
        if (mainForm == null) mainForm = new MainForm();
        boolean notLogin = Boolean.TRUE;
        while (notLogin) {
            notLogin = new LoginDialog().showDialog();
        }
        mainForm = new MainForm();
        mainForm.setVisible(true);
    }
 
    /** Method ini akan menginisialisasi object koneksi ke database yang akan 
     * digunakan di seluruh aplikasi. */
    private static void initDataBaseConnection() {
        try {
            MysqlDataSource dataSource = new MysqlDataSource();
            /* Setting koneksi ke database */
            dataSource.setUser("root");
            dataSource.setPassword("admin");
            dataSource.setDatabaseName("menulogin");
            dataSource.setServerName("localhost");
            dataSource.setPortNumber(3306);
 
            loginService = new LoginServiceImpl(dataSource.getConnection());
        } catch (SQLException ex) {
            Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
 
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        initDataBaseConnection();
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    UIManager.setLookAndFeel("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
                } catch (ClassNotFoundException ex) {
                    Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
                } catch (InstantiationException ex) {
                    Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
                } catch (IllegalAccessException ex) {
                    Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
                } catch (UnsupportedLookAndFeelException ex) {
                    Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
                }
                initLogin();
            }
        });
    }
}

    private class WorkerLogin extends SwingWorker<UserApp, Void> {
 
        @Override
        protected void done() {
            try {
                if (get() != null) {
                    notLogin = false;
                    closeLoginDialog();
                } else {
                    gl.replace(jProgressBar1, lblError);
                    txtUserName.requestFocusInWindow();
                    txtUserName.selectAll();
                }
                btnLogin.setEnabled(true);
                jProgressBar1.setIndeterminate(false);
                jProgressBar1.setVisible(false);
            } catch (InterruptedException ex) {
                Logger.getLogger(LoginDialog.class.getName()).log(Level.SEVERE, null, ex);
            } catch (ExecutionException ex) {
                Logger.getLogger(LoginDialog.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
 
        @Override
        protected UserApp doInBackground() throws Exception {
            /* Hilangkan ini jika digunakan pada production */
            Thread.sleep(1000);
            return Main.getLoginService().login(txtUserName.getText(),
                    String.valueOf(txtPassword.getPassword()));
        }
    }

    private void closeLoginDialog() {
        this.dispose();
    }

	...
    private WorkerLogin workerLogin;
 
    /** Creates new form LoginDialog */
    public LoginDialog() {
        super(Main.getMainForm(), Boolean.TRUE);
        initComponents();
        ...
    }

    private void btnLoginActionPerformed(java.awt.event.ActionEvent evt) {                                         
        /* Cek dahulu apakah workerLogin masih berjalan, kalau masih jalan
         * cancel dan set ke null */
        if (workerLogin != null && !workerLogin.isDone()) {
            workerLogin.cancel(true);
            workerLogin = null;
        }
 
        //TODO: cek untuk mengembalikan state lblError ke Progress Bar, 
        // bagaimana cara mengecek apakah lblError sudah ditambahkan atau belum ?
        try {
            gl.replace(lblError, jProgressBar1);
        } catch (java.lang.IllegalArgumentException ae) {
            // Do nothing here
        }
 
        workerLogin = new WorkerLogin();
        workerLogin.execute();
 
        /* Disable tombol LOGIN, tampilkan dan jalankan PROGRESS BAR */
        btnLogin.setEnabled(false);
        jProgressBar1.setVisible(true);
        jProgressBar1.setIndeterminate(true);
    }

    private void btnCancelActionPerformed(java.awt.event.ActionEvent evt) {                                          
        System.exit(0);
    }

    private void jMenuItem2ActionPerformed(java.awt.event.ActionEvent evt) {                                           
        /* Tutup form utama */
        this.dispose();
 
        /* Tampilkan LoginDialog-nya */
        Main.initLogin();
    }