Java and Linux: TrayIcon and Task Switcher issues

Question

I have an application that runs on Windows (great) and Ubuntu 12.04 (facing a couple interface issues). First, I have this code below to implement a TrayIcon:

if (SystemTray.isSupported()) {

    // Get the SystemTray instance
    SystemTray tray = SystemTray.getSystemTray();

    // Load icon
    java.awt.Image image = null;
    try {
        image = ImageIO.read(getClass().getResource("icon.png"));

    } catch (IOException exc) {
        exc.printStackTrace();
    }

    /**
     * A few listeners to popup menu items click.
     */

   // Create a popup menu and its items
   PopupMenu popup = new PopupMenu();
   MenuItem openItem = new MenuItem("Open");
   openItem.addActionListener(openListener);
   popup.add(openItem);

   popup.addSeparator();

   MenuItem closeItem = new MenuItem("Close");
   closeItem.addActionListener(closeListener);
   popup.add(closeItem);

   trayIcon = new TrayIcon(image, "app test", popup);

   try {
       tray.add(trayIcon);
   } catch (AWTException exc) {
       exc.printStaceTrack();  
   }
}    

This png icon is has a transparent backgrond. As I said, works fine on Windows. But on Linux it gets a white background. Also, when mouse is over its icon, a label (not tooltip) "JavaEmbeddedFrame" is shown.

My .desktop file (in /usr/share/application) is set as:

[Desktop Entry]
Encoding=UTF-8
Name=appTest
GenericName=appTest
Comment=Testing
Exec=/bin/sh "/usr/share/appTest/test.sh"
Icon=/usr/share/appTest/icon.png
Terminal=false
Type=Application
StartupNotify=true

When ALT+TAB, it isn't show "appTest" but "Java" with my application icon and a default Java icon (like another window) with "java.lang.Thread" description.

Any ideas of how to fix it? Thanks in advance!