[hibernate-issues] [Hibernate-JIRA] Commented: (HV-421) Reconsider behavior of parameter validation for inheritance hierarchies

[Hardy Ferentschik (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HV-421?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=39972#action_39972 ] 

Hardy Ferentschik commented on HV-421:
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{quote}
Parameter constraint checking currently happens when creating the meta-model (constructor of BeanMetaDataImpl). This means a bean with illegal method parameter constraints would cause an exception also if no method validation but only standard bean validation is performed on that bean. Personally I think such a fail fast approach is always preferrable (and if anyone annotes method parameters with constraint annotations he very likely will perform method validation at one point). WDYT?
{quote}
Generally I would also prefer with the fail fast approach. It is also consistent with the parsing/creating of BV constraints and we are talking about {{ConstraintDefinitionException}} here. 
Now comes the but. The method level validation is not part of the spec and potentially there could be other attempts to implement some form of method level validation. Or maybe some people used the constraints annotations on method parameters for "documentation" purposes. Maybe we have to be more conservative here to ensure we don't break pure Bean Validation behavior.

> Reconsider behavior of parameter validation for inheritance hierarchies
> -----------------------------------------------------------------------
>
>                 Key: HV-421
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HV-421
>             Project: Hibernate Validator
>          Issue Type: Bug
>          Components: engine
>            Reporter: Gunnar Morling
>            Assignee: Gunnar Morling
>             Fix For: 4.2.0.Beta2
>
>
> Let A extend B and A#foo() override B#foo(). When validating an invocation of A#foo() the current implementation will evaluate all parameter constraints defined at A#foo() *and* B#foo(). That way foo()'s preconditions defined in B are strengthened by A. 
> According to the ["Programming by contract"|http://en.wikipedia.org/wiki/Programming_by_contract] article on WP this is not allowed, subtypes may only weaken preconditions defined by supertypes. The common implementation pattern for this is to combine the preconditions within a hierarchy by a logical OR, meaning the weakest precondition in the hierarchy applies.
> Note that postconditions (return value constraints) may be strengthened (but not weakened) by subtypes. Therefore the current implementation (AND combination) should be correct here.

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