springframework-developer

[Springframework-developer] MultiActionController & Validation

[Tom N. <tom...@gm...>]

Hi spring devs --  I've got a suggestion that I'd like some help with.

I'm using the MultiActionController's binding and validation
capabilities (which by the way, I'd be glad to help there document a
little better...  )

Anyway, I'm trying to use the 'lazy' implementation, where my action
methods have the command object as the third parameter.  The problem
is, if there are validation errors, an exception is thrown (when
binder.closeNoCatch() is called on line 499 (rev 1.33).  The only way
to handle validation errors are:

1.  Don't do it the lazy way, and manually do binding/ validation
or
2.  override getExceptionHandler(Throwable exception) and create a
custom Exception handler for a ServletRequestBindingException.

Both of these could get tedious, so I'm wondering if we could make an
extension point, maybe call it handleValidationError(...) and call it
at the end of MultiActionController.bind(...) if there are validation
errors.  The default implementation could then call
binder.closeNoCatch().

Then the problem becomes, we'd normally want to return to the previous
view and display form errors....  That's where my idea fails.  Does
anyone else see this as an opportunity for enhancement?  I was going
to post an issue on JIRA, but I wanted to get others' input first.

Thanks!
-Tom

[Springframework-developer] MultiActionController & Validation

[Tom N. <tom...@gm...>]

Hi,  this is a post I originally sent to the springframework dev list,
and I never heard anything back -- I don't know if I didn't send it
correctly or what, but it appears that most of the action is on the
'user' list, so here's my original question:

---------------------------------------
Hi spring devs --  I've got a suggestion that I'd like some help with.

I'm using the MultiActionController's binding and validation
capabilities (which by the way, I'd be glad to help document a
little better...  )

Anyway, I'm trying to use the 'lazy' implementation, where my action
methods have the command object as the third parameter.  The problem
is, if there are validation errors, an exception is thrown (when
binder.closeNoCatch() is called on line 499 (rev 1.33).  The only way
to handle validation errors are:

1.  Don't do it the lazy way, and manually do binding/ validation
or
2.  override getExceptionHandler(Throwable exception) and create a
custom Exception handler for a ServletRequestBindingException.

Both of these could get tedious, so I'm wondering if we could make an
extension point, maybe call it handleValidationError(...) and call it
at the end of MultiActionController.bind(...) if there are validation
errors.  The default implementation could then call
binder.closeNoCatch(). (This all makes sense if you look @ the
MultiActionController source code, BTW.)

Then the problem becomes, when validation errors occur, we'd normally
want to return to the previous view and display form errors....  That's
where my idea fails, since we would want to be able to return a
ModelAndView (and MultiActionController.bind(..) returns void.  Does
anyone else see this as an opportunity for enhancement?  I was going
to post an issue on JIRA, but I wanted to get others' input first.

Thanks!
-Tom

Re: [Springframework-developer] MultiActionController & Validation

[Colin S. <co...@ex...>]

On 8/27/2006 10:38 PM, Tom Nichols wrote:
> Hi,  this is a post I originally sent to the springframework dev list,
> and I never heard anything back -- I don't know if I didn't send it
> correctly or what, but it appears that most of the action is on the
> 'user' list, so here's my original question:
>
> ---------------------------------------
> Hi spring devs --  I've got a suggestion that I'd like some help with.
>
> I'm using the MultiActionController's binding and validation
> capabilities (which by the way, I'd be glad to help document a
> little better...  )
>   
Help in this area is welcome. You could attach any doc patches to a JIRA 
issue.
> Anyway, I'm trying to use the 'lazy' implementation, where my action
> methods have the command object as the third parameter.  The problem
> is, if there are validation errors, an exception is thrown (when
> binder.closeNoCatch() is called on line 499 (rev 1.33).  The only way
> to handle validation errors are:
>
> 1.  Don't do it the lazy way, and manually do binding/ validation
> or
> 2.  override getExceptionHandler(Throwable exception) and create a
> custom Exception handler for a ServletRequestBindingException.
>
> Both of these could get tedious, so I'm wondering if we could make an
> extension point, maybe call it handleValidationError(...) and call it
> at the end of MultiActionController.bind(...) if there are validation
> errors.  The default implementation could then call
> binder.closeNoCatch(). (This all makes sense if you look @ the
> MultiActionController source code, BTW.)
>
> Then the problem becomes, when validation errors occur, we'd normally
> want to return to the previous view and display form errors....  That's
> where my idea fails, since we would want to be able to return a
> ModelAndView (and MultiActionController.bind(..) returns void.  Does
> anyone else see this as an opportunity for enhancement?  I was going
> to post an issue on JIRA, but I wanted to get others' input first.
>   
Fundamentally, the MultiActionController was never meant to be used with 
a form. It doesn't know anything about form lifecycles. Now it didn't 
really have to be this way; the current split is somewhat unfortunate, 
basically as far as I'm concerned, the whole hierarchy above but not 
including SimpleFormController could have supported multi-action and 
multi-command (binding to many objects) handling, while 
SimpleFormController could have limited that down to multi-action and 
single command (binding to the one form object). The current split where 
multi-action is in a separate hierarchy reflects the organic way those 
classes evolved.

That said, I think it would possibly be simpler for you to extend 
SimpleFormController, and delegate yourself to a multi action 
strategy... You would not then have to worry about reimplementing any of 
the form lifecycle stuff.

Colin

---
Colin Sampaleanu
Principal, Interface21
Spring Training, Consulting and Support - "From the Source"
http://www.interface21.com

Re: [Springframework-developer] MultiActionController & Validation

[Tom N. <tmn...@gm...>]

Colin,

Thanks for the quick reply.  I'll take another look at adding
multi-action delegation to the SimpleFormController.  Is there any
plan to add an implementaiton to the Spring library?

I suspect if I were to extend SimpleFormController, I could re-use the
action resolver strategy but I would have to re-implement the handler
registering in MultiActionController.

Thanks again for the help.
-Tom