Exporting Active Objects and components as Web Services

Let's start with a simple example, an Hello world active object exposed as a web service:

public class HelloWorld implements Serializable {
   public HelloWorld () {}
   public String helloWorld (String name) {
      return "Hello world !";
   }
   public static void main (String [] args) {

    try {
        HelloWorld hw = (HelloWorld)PAActiveObject.newActive("HelloWorld", new Object []{});
        WebServices.exposeAsWebService(hw,
        "helloWorld","http://localhost:8080", new String [] { "helloWorld" }); 

    } catch (ActiveObjectCreationException e) {
            e.printStackTrace();
    } catch (NodeException e) {
            e.printStackTrace();
    }
   }
}

The active object hw has been deployed as a web service on the web server located at "http://localhost:8080" . The accessible service method is helloWorld.

Now that the server-side Web service is deployed, we can create a new client application in Visual Studio .NET.

In your new Visual Studio Project:

C3D is a Java benchmark application that measures the performance of a 3D raytracer renderer distributed over several Java virtual machines using ProActive. C3D is composed of several parts: the distributed engine (renderers) and the dispatcher that is an active objet. This dispactcher permits users to see the 3D scene and to collaborate. Users can send messages and render command to this dispatcher. This enhancement of C3D is to send commands to the dispatcher from any language. To perform such an enhancement, the Dispatcher object must be exposed as a web service in order to a C# client for example controls it. Only one instruction has been added in the main method:

WebServices.exposeAsWebService (dispatcher, "C3DDispatcher",
                    "http://localhost:8080",  new String [] {
                    "rotateRight", "getPicture", "rotateLeft", "rotateUp",
                    "rotateDown", "getPixels", "getPixelMax", "waitForImage",
                    "spinClock", "spinUnclock", "addRandomSphere", "resetScene",
                    "registerWSUser", "unregisterWSUser"
                });

Once the dispatcher is deployed as a web service, we have a WSDL url: http://localhost:8080/proactive/servlet/id=C3DDispatcher. It will be usefull to construct the dispatcher client.

First of all, we have to generate the service proxy following the steps described for the hello world access.

All the SOAP calls will be managed by the generated proxy localhost.C3DDispatcher.

C# client registers to the C3D dispatcher and then can send commands. C3D is a collaborative application. Indeed, when a client performs a call, all others users must be advised by the dispatcher. Although dispatcher can contact ProActive applications, it cannot communicate with other applications (it cannot initiate the communication). In other words, the dispacher must communicate remotely with an application written in another language.

The answer to this problem is to use .Net web service on the C# user machine. Such a web service is waiting for callback requests that come from dispatcher. When receiving a request, the service sends it to the client via a .Net Remoting shared object. Thus, when the .Net web service receives a callback request, the C# client is updated thanks to propagated events.

Here are screenshots of the user application: