How would I create an asynchronous notification system using RESTful web services?

Question

I have a Java application which I make available via RESTful web services. I want to create a mechanism so clients can register for notifications of events. The rub is that th

Answer 1

In the response to the RESTful request, you could supply an individualized RESTful URL that the client can monitor for updates.

That is, you have one URL (/Signup.htm, say), that accepts the client's information (id if appropriate, id of object to monitor) and returns a customized url (/Monitor/XYZPDQ), where XYZPDQ is a UUID created for that particular client. The client can poll that customized URL at some interval, and it will receive a notification if the update occurs.

If you don't care about who the client is (and don't want to create so many UUIDs) you could just have separate RESTful URLs for each object that might want to be monitored, and the "signup" URL would just return the correct one.

As John Saunders says, you can't really do a more straightforward publish/subscribe via HTTP.