RMI + Observable/Observer trouble

Question

I'm trying to develop the following:
Local:
A Swing JFrame object which contains some JPanels that should Observe the actions of server's BusinessLogic.java
Both sides:
An interface that contains the declaration of the methods in server's business logic.
RemoteObserver.java
RemoteObservable.java
RemoteObserverImpl.java
RemoteObservableImpl.java
Server:
One Observable class that contains the business logic and notifies some changes and implements the Interface.
Other classes.
I'm using the latest JDK version.
I have some classes to do the RMI + Observable/Observer thing but I don't know how to apply them to my application.
Here's what i've done so far:
public class MainFrame extends JFrame {
     public static final String serviceName = "RemoteServer";
     private String host = "localhost";
     private RemoteBusinessLogicInterface remoteLogic;
     public MainFrame(String frameTitle) {
          super();
          setTitle(frameTitle);
          setSize(700, 600);
          setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          System.setProperty("java.security.policy", "client.policy");
          setRemoteServer();
          ObserverPanel observerPanel = new ObserverPanel(
                    remoteLogic);
          getContentPane().setLayout(new BorderLayout());
          getContentPane().add(observerPanel, BorderLayout.CENTER);
          this.setVisible(true);
     public void setRemoteServer(){
          try {
               if (System.getSecurityManager() == null)
                    System.setSecurityManager(new RMISecurityManager());
               String rmiUrl = "rmi://" + host  + "/" + serviceName;
               remoteLogic = (RemoteBusinessLogicInterface) Naming.lookup(rmiUrl);
          } catch (ConnectException ex) {
          } catch (UnknownHostException ex) {
          } catch (Exception ex) {
     public static void main(String[] args) {
          MainFrame f = new MainFrame("Title");
public class ObserverPanel extends JPanel{
     private DefaultListModel items;
     private JList list;
     public ObserverPanel(RemoteBusinessLogicInterface remoteLogic) {
          items = new DefaultListModel();
          list = new JList(items);
          list.setVisibleRowCount(24);
          JScrollPane scrollPane;
          scrollPane = new JScrollPane(list);
          setLayout(new BorderLayout());
          add(scrollPane,BorderLayout.CENTER);
     public void update(RemoteObservable observable, Object objektua) {
          System.out.println("Change notified");
public interface RemoteBusinessLogicInterface extends RemoteObservable{
     public void insertData(int number, String code, Date date) throws RemoteException;
     public void submit() throws RemoteException;
     public void clear() throws RemoteException;
class RemoteBusinessLogic extends RemoteObservableImpl implements
          RemoteBusinessLogicInterface {
     public static final String serviceName = "RemoteServer";
     public RemoteBusinessLogic() throws RemoteException {
     public void clear() throws RemoteException {
          setChanged();
          super.notifyObservers();
     public void insertData(int number, String code,
               Date date) throws RemoteException {
          System.out.println("Something");
          setChanged();
          super.notifyObservers();
     public void submit() throws RemoteException {
          System.out.println("Something");
          setChanged();
          super.notifyObservers();
     public static void main(String[] args) {
          System.setProperty("java.security.policy", "client.policy");
          if (System.getSecurityManager() == null)
               System.setSecurityManager(new RMISecurityManager());
          try {
               RemoteBusinessLogic serverObject = new RemoteBusinessLogic();
               try {
                    java.rmi.registry.LocateRegistry.createRegistry(1099);
                    Naming.rebind(serviceName, serverObject;
                    System.out.println("Server launched");
               } catch (MalformedURLException e) {
               } catch (Exception e) {
          } catch (RemoteException e1) {
}RMI works OK, but I don't know how to tell the server which are his observers. I know I have to use the addObserver (RemoteObserver ro) method but I don't know how to tell the server which are the GUI instances (which are the observers) so that I can add them.
Any help will be welcomed. Thanks.
Bye.

Answer 1

Hello Vitor,
Simply have your clients give your observable server object a remote reference to their observer object.
It would look something like this:
server.addObserver(new Remote(myObserver));Your server object would keep a list of its observers, and call them whenever it wants, using some interface method like:observer.stateChanged(someData);Essentially, design it just as if the observers were local.
John