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

[Hardy Ferentschik]

I find two annotations also more intuitive and easier to read/understand.

+1 for explicit @CrossParameterConstraint + @Constraint

--Hardy

On 16 Jan 2013, at 10:19 AM, Emmanuel Bernard <emmanuel at hibernate.org> wrote:

> I must admit I have not made my mind. The small advantage I find in having two annotations is that it is readable at a glance what the constraint is even just by reading its javadoc (assuming @Documented). In the second approach, you need to explicitly put it in the javadoc or have your users access to the source code and parse the @Constraint
> 
> What do others think?
> 
> On 15 janv. 2013, at 15:14, Gunnar Morling <gunnar at hibernate.org> wrote:
> 
>> 2013/1/15 Emmanuel Bernard <emmanuel at hibernate.org>
>> I can live with that but we must make it crystal clear that in case of
>> ambiguity, we raise an exception. Otherwise, someone changing the method
>> sig might have some nasty surprises.
>> 
>> And which of the options
>> 
>>     @CrossParameterConstraint(validatedBy=MyCrossParameterValidator.class)
>>     @Constraint(validatedBy=MyGenericValidator.class)
>>     public @interface MyConstraint { ... }
>> 
>> vs.
>> 
>>     @Constraint(
>>         validatedBy=MyGenericValidator.class,
>>         crossParameterValidatorType=MyCrossParameterValidator.class
>>     )
>>     public @interface MyConstraint { ... }
>> 
>> would you prefer?
>> 
>> Personally I'd lean towards the latter, since there would be exactly one meta-annotation denoting an annotation as constraint annotation type, with all attributes for the required configuration.
>> 
>> If following the 2nd approach, we should IMO add a default clause to validatedBy() (set to the empty array), allowing for the convenient definition of cross-parameter only constraints. According to [1] this change would be binary-compatible.
>> 
>> But this is no strong preference, I could also live with the two separate annotations.
>> 
>> --Gunnar
>> 
>> [1] http://wiki.eclipse.org/Evolving_Java-based_APIs_2#Evolving_API_interfaces_-_API_methods
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