RequestFactory and offline clients

[Gilad Egozi]

Hello,

I'm trying to create an application which is able to work even when network is down.

The idea is to store data returned from RequestFactory on the localStorage, and to use localStorage when network isn't available.

My problem - I'm not sure exactly how to differentiate between server errors(5XX, 4XX, ...) and network errors.

(I assume that on both cases my Receiver.onFailure() would be called, but I still don't know how to identify this situation)

Any help would be appreciated,

Thanks,

Gilad.

[Thomas Broyer]

Throwing out ideas:

• you can tell network errors from server errors at the RequestTransport level: server errors go through response received, while network errors go through onError. If you can work offline thogh, I'm not sure you should differentiate them: Receiver#onFailure should be enough to turn to using the localStorage.
• you could use offline events (use RootPanel.get().addBitlessDomHandler to subscribe) and/or navigator.onLine() (use JSNI) to detect when you're offline (on supported browsers); see http://www.html5rocks.com/en/tutorials/offline/whats-offline/#toc-detect-offline
• there are good advice for architecturing your app for offline use on the now-defunct Gears doc: http://code.google.com/apis/gears/architecture.html (not sure if they're still valid, double-check with HTML5Rocks)
• You should abstract your storage and use IndexedDB (through JSNI for now) if available (and possibly WebSQL), as localStorage has performance concerns: http://hacks.mozilla.org/2012/03/there-is-no-simple-solution-for-local-storage/