Publish and Subscribe with CORBA Web Events
by David Houlding

Listing One
<APPLET CODE="corbabeans.DynamicRequestManagerApplet.class" 
    NAME="RequestManager" WIDTH="1" HEIGHT="1" MAYSCRIPT>
<PARAM NAME="useslibrary" VALUE="CORBA Beans">
<PARAM NAME="useslibrarycodebase" VALUE="CORBABeans.cab">
<PARAM NAME="useslibraryversion" VALUE="2,4,0,0">
</APPLET>

Listing Two
// The manager of all CORBA requests.
var manager;

// Load publish and subscribe proxies. Could load more ...
var publisher;
var subscriber;

function initialize() {
    // Set up out own error handler.
    window.onerror = handleError
    // Get handles to CORBA request manager, load proxies 
    // and connect to event channel.
    manager = document.RequestManager;
    publisher = manager.loadPublisher(
        "ChatChannel_publish.ser",
        "publisher",
        "", // Ignore my publish events.
        "publisherDisconnectEvent");
    subscriber = manager.loadSubscriber(
        "ChatChannel_subscribe.ser",
        "subscriber",
        "subscriberPublishEvent",
        "subscriberDisconnectEvent");
    connect();
}

Listing Three
package corbabeans;
import java.util.EventListener;
public interface DynamicEventListener extends EventListener 
{
    public void publish(DynamicEvent event);
    public void disconnect(DynamicEvent event);
}

Listing Four
function connect() {
   publisher.connect();
   subscriber.connect();
   window.status = 'Connected';
}

Listing Five
function disconnect() {
   publisher.disconnect();
   subscriber.disconnect();
   window.status = 'Disconnected';
}

Listing Six
function send() {
   publisher.publishString( document.ChatForm.NameTextField.value +
                            ": " +
                            document.ChatForm.InputTextField.value );
   document.ChatForm.InputTextField.value = "";
}

Listing Seven
function subscriberPublishEvent(event) {
   document.ChatForm.DialogTextArea.value += 
      event.getParameter().getValue() + "\n";
}

Listing Eight
function subscriberDisconnectEvent(event) {
    alert( "Disconnected subscriber from event channel. Please re-connect." );
    window.status = 'Disconnected';
}

Listing Nine
function handleError( message, url, lineNumber ) {
   alert( "An unexpected error occurred:" + message + "\n" +
          "In JavaScript client loaded from URL: " + url + "\n" +
          "In JavaScript function at line number: " + lineNumber + "\n" +
          "Please restart and try again." );
   return true;
}






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