JavaFX Form Validation

[Florian Brunner]

Hi,

I haven't worked with JSR-303, yet, but I would appreciate if the Java community could come up with a validation framework which can be used consistently on various layers.

If JSR-303 currently doesn't fit the needs of JavaFX, maybe the JavaFX team could get involved in JSR-303 to make sure it fits the needs of JavaFX as well?

Regards,
Florian

Am Montag 11 Juni 2012, 01:52:10 schrieb Jonathan Giles:
> Hi all,
> 
> I'm currently in the very, very early stages of developing a validation 
> API for future inclusion into JavaFX. I thought rather than get too far 
> into the research and development of a proof of concept, I would see 
> what you all think. Any feedback now would be very useful.
> 
> Essentially, there are a few common styles related to form validation. 
> Some of the more likely approaches include:
> 
>   * The 'JGoodies Validation framework' [1] approach, where the
>     developer provides a Validator that will then run over the form and
>     gather feedback to return to the user (for example, it would test
>     that the 'name field' is not empty, and that the email address is of
>     the correct style - if either of these rules are invalid, the
>     Validator would return ValidationMessage instances inside a
>     ValidationResult). If validation fails the user is shown the text
>     out of the ValidationMessage feedback, otherwise the form would
>     submit as per usual. This validation may happen at a number of times
>     (during form submission, when focus is lost, as a key is typed,
>     etc). The nice thing about this approach is that the Validator can
>     be a part of the domain model, the presentation model, or a separate
>     thing altogether.
>   * The JSR-303 approach which uses annotations to indicate the rules
>     applicable to each field. These annotations are on the domain model,
>     and therefore assumes that the form is directly tied to a domain
>     object (which may not always be correct). I think the JSR-303 API is
>     too complex for what is needed in JavaFX, but a similar
>     implementation could be developed with a simpler API that follows
>     this approach.
>   * For lack of a better reference point, the FXForm approach [3] which
>     encapsulates the validation inside a Form object that can be placed
>     in the scene. I know this isn't explicitly (in the case of FXForm)
>     about validation, but I think it is another approach to consider.
> 
> So, what does JavaFX need out of a validation framework? It's really 
> five things (I think):
> 
>  1. A way for developers to validate a form by providing some means of
>     specifying rules, as well as a way to specify when it runs, how it
>     is visually represented, etc.
>  2. A way for the validation to impact upon the visual state of the form
>     (using consistent CSS pseudoclass states / style classes, as well as
>     by showing custom overlays, error messages beside the component (or
>     grouped together at the top of the form)). There must be API to
>     specify all of this.
>  3. Convenient API to simplify the validation process [3] (e.g.
>     isEmpty(String), isAlphanumeric(String), etc, etc, etc).
>  4. An API that does not require it be integrated with UI controls.
>     Doing so would prevent 3rd party UI controls to be able to be
>     validated without also implementing the API, which may prove
>     burdensome. Instead, the validation API should be separate.
>  5. A means to integrate nicely with the bindings and properties API
>     present in JavaFX today.
> 
> Of the three approaches above, my personal preference is to follow the 
> JGoodies approach as I think it is the most powerful and flexible. 
> However, nothing is set in stone and I want to learn what others think.
> 
> Note that at present this research does not extend to considering 
> whether there should be API related to automatically generating a form 
> from a (JavaFX) bean (and making use of the validation API to ensure the 
> input is correct). However, I am not against discussing this topic as 
> well, as long as it too integrates nicely with the rules above, as well 
> as the validation API itself, obviously. This research may full into 
> requirement three above.
> 
> [1] http://www.jgoodies.com/freeware/libraries/validation/
> [2] https://github.com/dooApp/FXForm2
> [3] 
> http://www.jarvana.com/jarvana/view/com/jgoodies/validation/2.0.1/validation-2.0.1-javadoc.jar!/com/jgoodies/validation/util/ValidationUtils.html
> 
> Thanks,
> -- Jonathan
> 
>