[hibernate-issues] [Hibernate-JIRA] Issue Comment Edited: (HV-421) Reconsider behavior of parameter validation for inheritance hierarchies
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http://opensource.atlassian.com/projects/hibernate/browse/HV-421?page=com...
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Hardy Ferentschik edited comment on HV-421 at 2/8/11 7:10 AM:
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{quote}
Other implementations choose to prohibit multiple preconditions in a hierarchy at all
(e.g. Microsoft's Code Contracts). Given the complexity of the matter at hand and the
chance we might get something wrong here, I feel we might well start with such a
conservative approach in 4.2 and add support for the inheritence scenario later on. WDYT?
{quote}
I prefer this approach as well.
was (Author: hardy.ferentschik):
{quote}
Other implementations choose to prohibit multiple preconditions in a hierarchy at all
(e.g. Microsoft's Code Contracts). Given the complexity of the matter at hand and the
chance we might get something wrong here, I feel we might well start with such a
conservative approach in 4.2 and add support for the inheritence scenario later on. WDYT?
{quote}
I think I prefer this approach as well.
Reconsider behavior of parameter validation for inheritance
hierarchies
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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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