WebFlow idea.

[klr8]

This "end current flow and retry in parent" logic is indeed supprisingly robust. The original Ervacon web flow system provided a "SubFlowBackNavigationExceptionResolver" that also implemented this.

Anyway, it's still not a 100% solution and it does feel a bit "dirty". That's why we didn't add anything like that so far.

Erwin

[klr8]

Just letting you guys know that we have added continuations support to the web flow system recently. This should be included in the preview 2 release that's coming in a few days.

(For those not aware of continuations, read http://www-128.ibm.com/developerwork.../j-contin.html.)

Continuations allow you to make the flow 100% robust during free navigation (refresh, back button, ...), even when using sub flows. They also make it possible to do cool things like have multiple browser windows open in the same flow (e.g. using CTRL-N)!

We now have a system with pluggable flow execution storage strategies, so all of this is completely pluggable:

* classic storage in the HttpSession (like in SWF preview 1)
* server side continuations (stored in the HttpSession)
* client side continuations (stored on the client)
* ...

And all of this even without any impact on the pages! Each flow in your app can also have a different storage strategy!

So far we have only found 1 issue with this: application transactions don't work anymore when you're using continuations. We're not sure yet how we're going to tackle this. You could even argue "free browsing -- made possible by continuations -- is not compaticle with application transaction", so basically not supporting it. An advaced continuations storage strategy might also be able to work around the issue (e.g. clearing the token in all 'cloned' continuations in the storage when an application transaction ends).

Any input you guys might have would be much appreciated!

Erwin