MessageController receives message from client and send back a reply

MessageController.java

package gwt.user.server;
import org.jboss.errai.bus.client.api.base.MessageBuilder;
import org.jboss.errai.bus.client.api.messaging.Message;
import org.jboss.errai.bus.client.api.messaging.MessageCallback;
import org.jboss.errai.bus.client.api.messaging.RequestDispatcher;
import org.jboss.errai.bus.server.annotations.Service;
import com.google.inject.Inject;

@Service
public class MessageController implements MessageCallback {

 // https://docs.jboss.org/author/display/ERRAI/Dependency+Injection
 @Inject
 private RequestDispatcher dispatcher;

 public MessageController() {}

 public void sendMessage() {
  MessageBuilder.createMessage()
   .toSubject("ClientService")
   .signalling()
   .with("text", "Hi There")
   .noErrorHandling()
   .sendNowWith(this.dispatcher);
 }

 public void callback(Message message) {
  System.out.println("MessageController received message");
  this.sendMessage();
 }

}