Hi Davis,
Yes, using GWT-RPC. My problem was that I "forgot" that I'm dealing
with an asynchronous call. I was trying to populate the field on my
form with data before the call had successfully returned. So, I was
getting a Null Pointer Exception from the object I was fetching. Once I
realized this, I moved my code to populate the field into the
onSuccess() method and it's all happy.
Thanks for the reply!
Dave
Davis Ford wrote:
> Are you using GWT-RPC? �I'm not sure I understand your problem
> completely. �
>
> So if I have a service like:
>
> public interface MyService extends RemoteService {
> �� public Entity fetchEntity(String id);
> }
>
> public interface MyServiceAsync {
> �� �void fetchEntity(String id, AsyncCallback<Entity> callback);
> }
>
> then, in the GWT code, something triggers the service. �Typically it
> is via a button click or some event. �You seem to indicate that you
> are doing it by passing the id as a URL parameter, like:
>
> http://host/my.gwt.application/Application.html?id=123
>
> You should be able to parse the URL using the
> Window.Location.getPath() to get the url param with a regex.
>
> Once you have that, you do this:
>
> MyServiceAsync service = GWT.create(MyService.class);
>
> service.fetchEntity(id, new AsyncCallback<Void>() {
> �� � onFailure(Throwable t) {
> �� � � � �Window.alert("service call failed: "+t.getMessage());
> �� � }
> �� � onSuccess(Entity e) {
> �� � � � // do something with the entity
> �� � }
> });
>
> After onSuccess( ) -- you populate the form with whatever. �
>
> On Mon, Nov 16, 2009 at 5:02 PM, David C. Hicks <[email protected]
> <mailto:[email protected]>> wrote:
>
> I'm sure I must be making this harder than it needs to be, but I'm
> having zero success doing it.
>
> Entering a new form, I'd like to display the name of an entity
> that was
> selected on the the calling page. �The calling page is a Struts2
> JSP, so
> I don't have the entire entity. �I only have the entity's ID,
> passed in
> as a parameter on the request URL. �That's easy enough to get, and I
> even have a service set up to go get the full entity once I have the
> ID. �The problem is that the service is asyncronous. �So, I get a Null
> Pointer Exception at the point where I try to set the data I'm
> retrieving into a label because the call hasn't yet completed.
>
> I'd rather not pass the name on the request URL - trying to avoid the
> messy encoding/decoding problems. �I've tried to create an
> AsyncCallback
> class that included a hook that I could "wait" for, but this only
> seemed
> to create an infinite wait loop.
>
> So, now I'm wondering if I need to somehow "bind" the retrieved
> data to
> a field on my form so that it will populate when the call completes.
> Then again, maybe this is overkill, too.
>
> Is there a better way to solve this problem?
> Thanks,
> Dave
>
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