REST is a powerful architecture because of its loose coupling design that facilitates a high level of interoperability. However, even the dissertation that defines REST states that one of the trade-offs of REST is that it “degrades efficiency, since information is transferred in a standardized form rather than one which is specific to an application’s needs”. That is, you might be able to achieve more efficient operation using a mechanism that goes beyond REST’s uniform interface, that is more specific to your application. This comes at the price of a loss of interoperability and should only be used if necessary, but with this in mind, let’s look at a good way to use RPCs that integrate with Dojo‘s REST module, the JsonRestStore. This approach builds on the REST architecture, while allowing exceptions as needed.
There is growing support in browsers for offline capabilities with the HTML 5 specification for local storage, offline notifications, and offline application cache, but adapting an application to store changes locally and do synchronization when connectivity is restored remains a major challenge for developers. Dojo 1.2’s new dojox.rpc.OfflineRest module automates the local storage of data and synchronization by leveraging the Dojo Data and REST abstractions. The OfflineRest module augments the JsonRest service in Dojo such that requests are cached in local storage for offline access, and modification requests (put, post, and delete) modify the cache and are recorded for delivery to the server; immediately if online, otherwise when connectivity is restored. Furthermore, JsonRest is the core engine used by JsonRestStore. Consequently, you can simply use the standard Dojo Data API with the JsonRestStore and effortlessly add offline capability with no modifications to your data interaction code. The underlying Rest service automates the handling of caching, storing data locally, and syncing changes. In addition the new OfflineRest module has no dependency on plugins, but rather progressively utilizes offline features that are available, while still operating properly on legacy browsers without offline support.