The actor pattern framework is a powerful mechanism for inter process communication. The framework (mainly) supports communication between actors.
One of the main benefits of the abstraction is that you can easily create an asynchronous message based system, which is suitable for (particularly) a Swing application. As Swing (as almost all GUI libraries) is based on a single thread model, you need to pass any real work to a worker thread - unless you do not mind creating a sluggish application.
Actors in SemiSpace extend the Actor object. The object offers send, receive and the optional methods getReadTemplates and getTakeTemplates. A typical "manager" actor will register templates it want to react on. For instance, an OrderManager actor will want to receive Orders, place by a Client actor.
The following declaration is annotated with SwingActor which makes the receive call executed on the Swing thread, which is essential when you are changing values that shall be displayed in the GUI.
@SwingActor
public class SwingActorSearch extends Actor {
Sending an actor query is performed with send. The example fills out an address query template, and sends it to whichever actor that is willing to answer. The receiving actor can, of course, reside in a server process (which is the case in the tutorial).
AddressQuery query = new AddressQuery(); query.setAddress(address); send( query );
After the "search manager" actor has performed the query, it will reply to the sender by using the originator identification field on the payload as destination address. This makes the answer go directly to the actor which made the query, and the answer is given in in the receive method:
public void receive(ActorMessage msg) {
if ( msg.isOfType(GoogleAddress.class)) {
swingAction.setEnabled(true);
fillArea.setText(msg.getPayload().toString());
} else {
log.warn("Unexpected message: "+msg.getPayload().getClass().getName());
}
}
