What is error?

[kien kun]

public String getMessage(int n) throws RemoteException {
        String m = "<RMI & JDBC Chat>\n";
        String driver = "com.mysql.jdbc.Driver";
        String url = "jdbc:mysql://localhost:3306/";
        String username = "root";
        String password = "";
        String dbName = "rmi";
        Connection con = null;
        try {
            String sql = "select * from rmi";
            Class.forName(driver).newInstance();
            con = (Connection) DriverManager.getConnection(url + dbName, username, password);
            Class.forName("com.mysql.jdbc.Driver").newInstance();
            Statement stmt = (Statement) con.createStatement();
            ResultSet rs = stmt.executeQuery("SELECT * from message");
            while (rs.next()) {
                m = m + rs.getString(1) + "\n";
            }
        } catch (Exception e) {
            System.out.println(e.getMessage());
            e.printStackTrace();
        }
        return m;
    }

I had tried to connect mysql with rmi.But has a exception?
What is it?

Mar 19, 2012 4:38:45 PM rmi.Client jButton1ActionPerformed
SEVERE: null
java.rmi.NotBoundException: server
        at sun.rmi.registry.RegistryImpl.lookup(RegistryImpl.java:106)
        at sun.rmi.registry.RegistryImpl_Skel.dispatch(Unknown Source)
        at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:386)
        at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:250)
        at sun.rmi.transport.Transport$1.run(Transport.java:159)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.rmi.transport.Transport.serviceCall(Transport.java:155)
        at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:535)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:790)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:649)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
        at java.lang.Thread.run(Thread.java:619)
        at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:255)
        at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:233)
        at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:359)
        at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
        at java.rmi.Naming.lookup(Naming.java:84)
        at rmi.Client.jButton1ActionPerformed(Client.java:91)
        at rmi.Client.access$000(Client.java:25)
        at rmi.Client$1.actionPerformed(Client.java:51)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
        at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
        at java.awt.Component.processMouseEvent(Component.java:6134)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
        at java.awt.Component.processEvent(Component.java:5899)
        at java.awt.Container.processEvent(Container.java:2023)
        at java.awt.Component.dispatchEventImpl(Component.java:4501)
        at java.awt.Container.dispatchEventImpl(Container.java:2081)
        at java.awt.Component.dispatchEvent(Component.java:4331)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4301)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3965)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3895)
        at java.awt.Container.dispatchEventImpl(Container.java:2067)
        at java.awt.Window.dispatchEventImpl(Window.java:2458)
        at java.awt.Component.dispatchEvent(Component.java:4331)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

[Chris Janicki]

You need to read the exception. It says the error occurred in your code at line #91 of Client.java. You're doing an RMI lookup() there, and the thing you are looking up is not found. You probably have the wrong name for the remote object. Find out what name the remote object used when it registered itself, and verify that it actually does so.