[bv-dev] Bean Validation and JavaFX

[Edward Burns]

>>>>> On Sat, 30 Jun 2012 19:53:20 +0200, Gunnar Morling <gunnar at hibernate.org> said:

EmmanuelB> It might make sense for us to add support of JavaFX types in
EmmanuelB> the spec.  Implementations could use some lazy "binding" in
EmmanuelB> case JavaFX is not there.  Are these types stable and few or
EmmanuelB> do they change every other morning?

GM> Personally, I find the option of adding support for types of specific
GM> APIs/frameworks to BV not really appealing. Maybe another API than
GM> JavaFX appears tomorrow?

GM> Another problem I see with GUI validation is that one typically wants
GM> to validate form values before putting them into the model. This works
GM> fine for property-level constraints (using Validator#validateValue()),
GM> but we have nothing to offer for class-level constraints here.

EmmanuelB> That would mean some small duplication but the form itself is
EmmanuelB> an object right? We could put the (class level) constraint
EmmanuelB> declarations on it.

GM> I'm not really sure. AFAICS the form/controller class would have
GM> members of types such as Label, TextField etc, while the a validator
GM> for a class level constraint of the model would operate on the bean's
GM> attribute types. One could think about creating a second validator for
GM> the form types. But I'm not really a JavaFX expert :)

For what it's worth, this "validate values before putting them into the
model" is *exactly* what the BV + JSF integration has always done, since
JavaEE 6.  Here's some text from the JSF spec about it [1].

  Obtain the ValidatorContext from the ValidatorFactory.

  Decorate the MessageInterpolator returned from
  ValidatorFactory#getMessageInterpolator with one that leverages the
  Locale returned from UIViewRoot.getLocale(), and store it in the
  ValidatorContext using ValidatorContext#messageInterpolator.

  Obtain the javax.validation.Validator instance from the
  validatorContext.

  Obtain a javax.validation.BeanDescriptor from the
  javax.validation.Validator. If hasConstraints() on the BeanDescriptor
  returns false, take no action and return. Otherwise proceed.

  Call javax.validation.Validator#validateValue, passing valueBaseClass,
  valueProperty, the value argument, and validatorGroupsArray as
  arguments.

  If the returned Set<ConstraintViolation> is non-empty, for each
  element in the Set, create a FacesMessage where the summary and detail
  are the return from calling ConstraintViolation#getMessage. Capture
  all such FacesMessage instances into a Collection and pass them to
  ValidatorException.ValidatorException(java.util.Collection), throwing
  the new exception.

>>>>> On Sun, 1 Jul 2012 13:00:52 +0200, Gunnar Morling <gunnar at hibernate.org> said:

GM> Today BV is focused on actual Java types adhering to the JavaBeans
GM> convention (types with getters/setters), but there are use cases where
GM> one may have another type model but still would like to use the BV
GM> validation approach.

GM> My thinking was to provide an SPI which allows to customize the way BV
GM> interacts with type models. This SPI would establish an abstract type
GM> model used by the BV runtime. This model would know about "types",
GM> "properties" and so on, but these wouldn't necessarily have to be
GM> actual Java types with bean properties.

Gunnar, is it possible for you to craft this usage of BV in terms of a
pattern of invoking the validateValue() method rather then inventing
another SPI, which, by its very nature of being "yet another SPI" is
bound to be seen as baroque at some level?

>>>>> On Sun, 1 Jul 2012 15:13:50 +0200, Emmanuel Bernard <emmanuel at hibernate.org> said:

EmmanualB> Yes I am not convinced there us such demand for such
EmmanualB> feature. And that would definitively be a big undertaking.
EmmanualB> What do others think?

I'd like to avoid it if possible.  It's hard enough for one to get one's
head around what we have already, when coming in from the outside, and
looking at JavaEE as a whole.

Ed

[1] https://maven.java.net/service/local/repositories/releases/archive/javax/faces/javax.faces-api/2.1/javax.faces-api-2.1-javadoc.jar/!/javax/faces/validator/BeanValidator.html#validate(javax.faces.context.FacesContext,%20javax.faces.component.UIComponent,%20java.lang.Object)

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