Is the command pattern compatible with RESTful web services?

Question

Google recommends the use of the command pattern when building complex GWT applications. The idea seems to have some merit and various frameworks have been developed to help. However, most of the examples I found are using GWT-RPC for client/server communication.

We are considering developing a RESTful web service for our Java backend -- and using that for client/server communication (possibly using a framework like Resty).

But is the command pattern even compatible with Rest web services? What would those Rest URLs look like? How would command batching and undo be supported?

Answer 1

The command pattern is/was a recommended pattern and is a massive step forward from building an RPC interface using the RemoteService and RemoteServiceServlet which is pretty much all that was available at the time of the Google I/O presentation you refer to.

The GWT-RPC approach is very good and works well and provides the batching and undo mechanism. I have to say I've never implemented a single undo() function on any of my handlers although I do make use of batching.

A newer approach would be to use RequestFactory and map your code onto your service. This does support batching but not undo. It's not a great deal of work to implement but does have its peculiarities. A nice example can be found here.

If you need a REST interface then making use of this in your GWT to save developing two interfaces seems like a sensible idea. But as @Riley Lark says you'll have to write your own batching (and undo() if you need to).

My feeling is that both batching and undo don't really fit with the REST approach, but that's just my opinion. There's some more info here from a similar question.

Perosnally I would probably make use of GWTs infrastructure and RequestFactory to do client to server comms and take advantage of the batching and the optomised protocol and the cross site scripting protection and write a separate REST interface for whatever needs to use it.

Answer 2

You would have to implement batching yourselves if you don't use some package that supports it. At our company we decided to go with a straight REST interface - the expense of writing our own batching over a single API was less than the expense of making a RequestFactory API and a public API.

You'd have to somehow encode your multiple rest urls and payloads into a single url and payload!