RequestFactory : Get deltas from server's changes?

[JB]

Hi,

from what I read, I understood that RF allows to easily fire changes from client with only "deltas" in the payload.

What about the reverse? 

I'm trying to implement a service that would automatically fire changes coming from server side to the client.

Thanks for your help

[Thomas Broyer]

Basically, RF keeps 2 copies of your proxies: the immutable one you received from the server, and the mutable one created by RequestContext#edit(). Both proxies have a reference on each other (the immutable one using its reference to the mutable proxy as a "lock" to prevent creating two mutable proxies of the same immutable proxy).

When you fire() your RequestContext, RF uses AutoBeanUtils.diff() to get the differences between the immutable and the mutable proxy (after using AutoBeanUtils.getAutoBean() to retrieve the AutoBean for each proxy), and uses that map to build the request payload.

On the server-side, when receiving the diff, the servlet retrieves the entity (using its find static method or a locator) and then loops through the diff to call setters on the object. Note that at this time, RF works on the @ProxyFor-ed entity, not a proxy (a proxy is created to wrap the entity at a later time, to easily traverse its properties, for building the response).

So if you can do that swapping the client and server sides, then you're all done. I believe it's possible, maybe not that easy though. First, it implies that you keep a "cache" (on the client side) of all proxies that could have changes applied to them, then you need to apply those changes without the need to edit() the proxies (that's easy, go down to the AutoBean level); but you'd then (probably) have to be careful if you are also edit()ing a given proxy at the same time.