Validating initial input parameters for a pageflow

[sonstone]

I would like to require an initial set of request parameters that get passed into a pageflow. Depending on whether those parameters are valid, I'd like to redirect to an error page. Ideally, I'd like to map those parameters to a model and use annotations to define the validation rules. Does anyone have any advice on the cleanest way of doing this?

The three biggest questions in my head are:

1) how do I map the initial set of parameters to a model because I can't use the h:inputText at this point?
2) if I were to get it in a model how could I manually run the validation rules on the model within a decision node?
3) is it even possible to start a flow with a decision? All of the examples I have seen begin with a start-page.

These questions admittedly imply a very specific approach to the problem. I am open to any other suggestions that would provide the same result.

Thanks in advance,

Daniel

[gavin.king]

1) Use Seam page parameters
2) Try using Validators.instance().....
3) No, but you can do the validation in a Seam page action, and if the validation succeeds, begin the pageflow

Note that I have never tried to do this, but I believe that the above will work.