On Wed, Oct 29, 2008 at 10:37 AM, Brian <[EMAIL PROTECTED]> wrote:
> Sounds good.
> Is the gwt-rpc format described, so I could write a non-gwt app (say,
> a mac desktop gadget) that hits my server using the same api as the
> gwt-rpc browser app? Note, I don't actually care right now what the
> format is, just that the protocol is described, and is easy to impl in
> a non-gwt-rpc-browser app (like it is with json ;-)
I think Jason and Walden gave pretty good answers, but I thought I'd
give a little more detail.
The GWT RPC format is intentionally opaque JSON. This makes it
somewhere between difficult and impossible to add a non-GWT agent to
the RPC discussion. There isn't really a nice work-around for
creating a non-Java server-side implementation but, because your
RemoteServiceServlet implementation just has to implement your
synchronous RPC interface, it's quite possible for non-GWT clients to
talk to the same server-side business logic, just without using the
RPC protocol.
The easiest way to implement RPC on the server is like this:
public interface HelloWorld extends RemoteService {
String sayHi(String name);
}
public class HelloWorldServlet extends RemoteServiceServlet implements
HelloWorld {
public String sayHi(String name) {
return "Hello, " + name;
}
}
In a GWT client, you'd use it like this:
// you need to maintain an Async interface in parallel to the service definition
public interface HelloWorldAsync {
void sayHi(String name, AsyncCallback<String> callback);
}
HelloWorldAsync service = (HelloWorldAsync) GWT.create(HelloWorld.class);
service.sayHi(new AsyncCallback<String>() {
public void onFailure(Throwable caught) {
// handle server-side errors and networking errors
}
public void onSuccess(String response) {
Window.alert("Server says: " + response);
}
});
So, from a GWT perspective, it's _really_ easy. The point I'm trying
to make here, though, is that the server side is just an
implementation of an interface. It's possible (using the class named
RPC) to implement that interface on one class and answer HTTP POST
request in a different class (the above example does everything in one
class by subclassing RemoteServiceServlet). Separating the business
logic from the HTTP request-handling means that you can re-use the
business logic to support non-GWT clients in whatever fashion you
like, including standard Java RMI, and RESTful webservices.
On Wed, Oct 29, 2008 at 10:45 AM, Brian <[EMAIL PROTECTED]> wrote:
> I care heavily about the wireformat of my requests. Maybe that's
> because I have bugs in my json api from time to time, but it's very
> handy to fire up ethereal/wireshark and check what's happening on the
> wire. But I hear ya, it'd "be nice" if I didn't have to care, I just
> do.
> Is the wireformat plaintext? Is it published?
> Thanks everone for the info. Guess I got my answers, and I should
> start hitting the api docs on gwt-rpc if I start going down this road.
The wire format is plain text. It's actually JSON. It's just
unreadable JSON because the assumption is that both the producing and
consuming code is auto-generated and can make all kinds of assumptions
about the structure of the text.
I've explained the wire format in copious detail in previous posts to
either this list or the GWT-Contributors list. If you're interested
in the gory details, you could search for those old posts. Just be
aware that I was explaining the format as it was used in GWT 1.4. The
RPC guts have changed very slightly since then to support a few
features in custom field serializers. Also, I think GWT 1.5 has
redefined or stopped using some of the flags that were available in
the old format. In other words, the spirit of the format is still the
same, but there might be some differences in the details now.
Ian
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