Re: Resubmitting RequestFactory request when server side logic requires it

On Monday, June 4, 2012 10:17:52 PM UTC+2, Ryan McFall wrote:

I am having issues when I want to resubmit some requests to the server
when the server-side logic indicates it should happen.  In particular,
here's what happens:

1.  The user logins in, which causes an object (SurveyResponseHeader)
to be created on the server-side, and sent back to the client.  edit
is then called on the client side on that object.

2.  The user fills in a set of SurveyResponse objects into a list
contained by the SurveyResponseHeader object (and a corresponding
request is made to save the object on the server).

3.  The user submits the survey responses, but the session has timed
out on the server.  An error code is sent back to the client, and the
user is asked to re-authenticate.

At this point, I want to resubmit the request that caused the error;
it should succeed on the server now because the session has been
restarted.  However, I can't use the same request object because I'll
get the "request is already in progress" error message.

Rather than tell you everything I've tried, I'd like to hear what
people think is the right way to accomplish this.  I can provide more
details if needed, but I want to keep the description simple at least
to start.

You have to make sure you convey the session-expiry-error as a "transport error" or "general failure", and not as a "service method return value".

Using the DefaultRequestTransport, any non-200 response from the server will be a "transport error", so handling session expiration from a servlet filter on the server and responding with a non-200 status code (let's say, for instance, a 401, or 400; make sure you don't redirect to your login page though!) should Just Work(tm).

To tell the difference between a real server failure and session expiration though, you'll have to make your own RequestTransport on the client (possibly extending DefaultRequestTransport) and define some kind of "protocol" (shared knowledge) with the server. Have a look at how it's done in the MobileWebApp sample in the GWT SDK: http://code.google.com/p/google-web-toolkit/source/browse/trunk/samples/mobilewebapp/src/main/java/com/google/gwt/sample/gaerequest/ It's specific to Google AppEngine but is really easy to adapt to whatever you use. The trick is to make sure you don't set a <security-constraint> on the RequestFactoryServlet in your web.xml, and instead handle the absence of authenticated user from code (in a servlet filter is the easiest)

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