First off, I love thata GWT 2.0 includes native support for JSON-P
requests!
However, I can't quite dump my own JSONP implementation in favor of
the new GWT counterpart. Reason: my JSON-P web service requires OAuth
signatures.
Details:
Unfortunately, neither the (HTTP) RequestBuilder nor the
JsonpRequestBuilder allow you to change the URL much in a way that
allows me to sign my requests for OAuth in a friendly way. Because of
this, I have abstracted my own implementation of a Request object so I
can hand the Request off to a UrlSigner before converting it to a
RequestBuilder or JsonpRequestBuilder.
Unfortunately, the JsonpRequestBuilder does not add the "callback"
parameter until invoking the send method, at which point it is too
late to re-sign the request. Also, there is no way provided to set a
known callback value, or even query the request to determine what it
is. This means my URL cannot be properly signed via OAuth since I do
not know the value of the callback parameter when I sign the URL.
Perhaps my previous implementation will provide some inspiration as to
how a similar level of functionality could be included in the GWT-
provided JsonpRequest[Builder]:
public class JSONPRestService extends AbstractRestService {
private static int cbIndex = 0;
private Map<String, Callback> callbacks = new HashMap<String,
Callback>();
@Override
public void get(String uri, Callback cb, JavaScriptObject params)
{
String callback = reserveCallback();
this.callbacks.put(callback, cb);
JSONObject jParams = params == null ? new JSONObject()
: new JSONObject(params);
jParams.put("callback", new JSONString(callback));
// Abstracted Request model that can be manipulated before
signing...
RequestProxy rp = super.buildRequest(Method.GET, uri, jParams
.getJavaScriptObject());
// Url Signing process, which includes the callback parameter
OAuthParams op = new OAuthParams();
op.signatureLocation = OAuthSignatureLocation.QUERYSTRING;
OAuth.signRequest(rp, op);
ScriptElement tag = Document.get().createScriptElement();
tag.setLang("JavaScript");
tag.setSrc(rp.url);
createCallback(this, callback, tag);
Document.get().getBody().appendChild(tag);
}
private native void createCallback(JSONPRestService svc, String
cbName,
Element tag) /*-{
$wnd[cbName] = function(results){
[email protected]::proceed
(Ljava/lang/String;Lcom/google/gwt/core/client/JavaScriptObject;Lcom/
google/gwt/dom/client/Element;)(cbName, results, tag);
};
}-*/;
@SuppressWarnings("unused")
private void proceed(String cbName, JavaScriptObject results,
final Element tag) {
Callback cb = this.callbacks.remove(cbName);
cb.execute(results);
DeferredCommand.addCommand(new Command() {
public void execute() {
Document.get().getBody().removeChild(tag);
}
});
}
private String reserveCallback() {
return "__" + GWT.getModuleName().replaceAll("\\.", "_") +
"__"
+ JSONPRestService.cbIndex++;
}
}
--
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