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

[Gunnar Morling (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HV-421?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=39980#action_39980 ] 

Gunnar Morling commented on HV-421:
-----------------------------------

The documentation use case you're mentioning is a good point. I'll keep the constraint check then in BeanMetaDataImpl's constructor, but I will actually raise the exception only if validateParameter()/validateAllParameters() is invoked. That way the validity check is still performed only once but an exception will only be thrown, if the method validation feature is actually used. And anyone using the constraints at parameters for documentation purposes in a way unsupported by HV won't get a problem, until he decides to perform method validation.

> 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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