Expert Spring MVC and Web Flow

This controller has a complex work flow, and we will break it down into its core compo-
nents. Then, we will show you the best extension points for altering the work flow in the
controller. We begin by illustrating all possible paths through the controller.
Figure 6-1 illustrates the many paths through the work flow of handling forms with
SimpleFormController.

Figure 6-1.SimpleFormController activity diagram

We will focus on the initial retrieval of the HTML form first. The controller uses the
method isFormSubmission()to determine if the HTTP request is either a form viewing or
form submission. The default implementation of this method merely checks the HTTP
method, and if it is a POST then isFormSubmission()returns true. The controller does not
consider a HTTP GET request a form submission. However, this method is not final, so your
implementation is free to define whatever criteria is appropriate to indicate the request
should be treated as a submission. If indeed the request is not a form submission, the

Resource requested

Retrieve form object from session

Everything from AbstractController

Is a form submission?Yes Is a session form? YesIs form bean in session?Yes

Create form object

Create and init binder

No

Create NewForm object

Create and init binder

No No

Remove from session

Bind request parameters to form object

Bind to form object

Store form in session

Should bind on NewForm?

Yes

No

Validate form object

Yes

onBindAndValidate

Validate on bind? Suppress validation?

Yes No

No

Yes

Collect reference data

No

Is a session form?

Display form view

No Handle form submit

Errors from binding or validation?

Yes

Done

CHAPTER 6 ■THE CONTROLLER MENAGERIE 151