Thursday, December 19, 2013

Need help with manipulating java originated objects in javascript

My goal is to initiate RPC calls directly from javascript.  I have come up with ways to fake callbacks (because of the asynchronous nature of RPC) but I can't figure out how to get custom objects into javascript.  

So, I've created a class named Interop and I statically create the service I'm interested in (had to use static as it was all I could get working, I don't think it's relevant right now):

    public class Interop {
        private static final GreetingServiceAsync service = GWT.create(GreetingService.class);
I then create a function that will do the async calls and handle the responses:

    public static void greetServer(final String success, final String failure) {
    new AsyncCallback<String>() {
    public void onFailure(Throwable caught) {
    callback(failure, caught.toString());

    public void onSuccess(String result) {
    callback(success, result);

Then I create a JSNI function to export this function to javascript which I call from the onModuleLoad():

    public static native void export() /*-{
$wnd.greetServer = $entry(@edu.washington.apl.imp.client.Interop::greetServer(Ljava/lang/String;Ljava/lang/String;));

And also create another JSNI function to deal with the callbacks:

    public static native void callback(String func, String response) /*-{

So that the function names I pass into greetServer() initially for success and failure are called by the JSNI as callbacks.  And this all works great when dealing with Strings or (I assume) a primitive type).  But when I try to do this with custom types (note the altered Custom type parameter):

    public static native void callback(String func, Custom response) /*-{

Then what ends up in javascript doesn't seem to work.  It seems to be a javascript object with cascading arrays and none of the methods are available.

So, the question is, how can Java-originated objects that aren't basic or primitives be accessed from within javascript (not JSNI)?  From what I can tell JavaScriptObject needs to originate in javascript, but in my case, my objects are originating in Java.  What can I do?

I've also looked into gwt-exporter and that shows how to instantiate java stuff from javascript, but not how to access java-originated stuff in javascript.

I know this is a bit confusing so please let me know if you have any questions.  Thanks!

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