Question

My understanding is that the GWT RequestFactory (RF) API is for building data-oriented services whereby a client-side entity can communicate directly with it’s server-side DAO.

My understanding is that when you fire a RF method from the client-side, a RequestFactoryServlet living on the server is what first receives the request. This servlet acts like a DispatchServlet and routes the request on to the correct service, which is tied to a single entity (model) in the data store.

I’m used to writing servlets that might pass the request on to some business logic (like an EJB), and then compute some response to send back. This might be a JSP view, some complicated JSON (Jackson) object, or anything else.

In all the RF examples, I see no such existence of these servlets, and I’m wondering if they even exist in GWT-RF land. If the RequestFactoryServlet is automagically routing requests to the correct DAO and method, and the DAO method is what is returned in the response, then I can see a scenario where GWT RF doesn’t even utilize traditional servlets. (1) Is this the case?

Regardless, there are times in my GWT application where I want to hit a specific url, such as http://www.example.com?foo=bar. (2) Can I use RF for this, and if so, how?

I think if I could see two specific examples, side-by-side of GWT RF in action, I’d be able to connect all the dots:

• Scenario #1 : I have a Person entity with methods like isHappy(), isSad(), etc. that would require interaction with a server-side DAO; and
• Scenario #2 : I want to fire an HTTP request to http://www.example.com?foo=bar and manually inspect the HTTP response

If it’s possible to accomplish both with the RF API, that would be my first preference. If the latter scenario can’t be accomplished with RF, then please explain why and what is the GWT-preferred alternative. Thanks in advance!

Answer 1

1.- Request factory not only works for Entities but Services, so you could define any service in server-side with methods which you call from client. Of course when you use RF services they are able to deal with certain types (primitive, boxed primitives, sets, lists and RF proxies)

@Service(value=RfService.class, locator=RfServiceLocator.class)
public interface TwService extends RequestContext {
  Request<String> parse(String value);
}

public class RfService {
public String parse(String value) {
  return value.replace("a", "b");
}

2.- RF is not thought to receive other message payloads than the RF servlet produces, and the most you can do in client side with RF is ask for that services hosted in a different site (when you deploy your server and client sides in different hosts).

You can use other mechanisms in gwt world to get data from other urls, take a look to gwtquery Ajax and data-binding or this article