[bv-dev] Distinguishing cross-parameter and generic constraints

[Emmanuel Bernard]

After letting this idea rest for a while, I still like it.

In the issue, you also proposed to go a step further and get rid of
@CrossParameterConstraint altogether. I sort of remember not being keen
on the idea to protect future evolutions on the type-safe
cross-parameter way. Have you thought about it more? What is your
opinion?

Emmanuel

On Mon 2013-01-07 23:21, Gunnar Morling wrote:
> Hi all,
> 
> As per the latest spec draft, a constraint must be either a cross-parameter
> *or* a generic constraint, but not both at the same time, as otherwise it
> would be ambiguous whether a constraint on a method refers to the method
> parameters or return value.
> 
> Most of the time this does not really pose a limitation, but some
> constraints actually might be both, cross-parameter *and* generic,
> depending on the specific context. Examples are @ScriptAssert in Hibernate
> Validator or generic constraints such as this:
> 
> @EqualPasswords
> public void register(String userName, String password, String
> confirmedPassword) {
> }
> 
> @EqualPasswords
> public class ResetPasswordRequest {
>     String userName;
>     String password;
>     String confirmedPassword;
> }
> 
> Based on a recent BVAL issue [1], I'm proposing to introduce a special
> constraint annotation attribute, "validationAppliesTo", allowing to specify
> the required behavior at the usage site:
> 
> @EqualPasswords(validationAppliesTo=PARAMETERS)
> public void register(String username, String password, String
> confirmPassword) {
> }
> 
> @EqualPasswords(validationAppliesTo=ANNOTATED_ELEMENT)
> public class ResetPasswordRequest {
>     String password;
>     String confirmedPassword;
> }
> 
> The following rules would apply:
> 
> * If a constraint is annotated with @Constraint and
> @CrossParameterConstraint, it must define a member "validationAppliesTo".
> The default value should be ANNOTATED_ELEMENT.
> * If a constraint is annotated with only one
> of @Constraint/@CrossParameterConstraint, defining a "validationAppliesTo"
> member doesn't have any special effect
> * Specifying validationAppliesTo=PARAMETERS anywhere except a method causes
> ConstraintDeclarationException
> 
> Any thoughts?
> 
> --Gunnar
> 
> [1] https://hibernate.onjira.com/browse/BVAL-340

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