[hibernate-issues] [Hibernate-JIRA] Commented: (HV-390) Boolean composition of constraints

[Dag Hovland (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HV-390?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=38847#action_38847 ] 

Dag Hovland commented on HV-390:
--------------------------------

We have been thinking about an alternative solution to the error reporting: Using some easy transformations on boolean expressions (deMorgans laws), we can "push" the negations "down" to the level of basic (not composed) tests. In this way, we do not need to give error messages for negated composed tests, only for negated simple tests. (This form is called "negation normal form" in logic). If we do this, then we can add a second error message to simple tests, which should be returned in the cases when the test should have failed. The rest of the error reporting can the remain as today. 

> Boolean composition of constraints
> ----------------------------------
>
>                 Key: HV-390
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HV-390
>             Project: Hibernate Validator
>          Issue Type: New Feature
>          Components: engine
>            Reporter: Federico Mancini
>            Assignee: Hardy Ferentschik
>             Fix For: 4.2.0
>
>         Attachments: modified classes.zip
>
>
> By adding a built-in annotation @Bool (or some other name) with element values OR, ALLFALSE and AND (which would be the default) it would be possible to 
> compose constraints in a boolean fashion.
> For example:
> {code}
> //Specify that at least one of the patterns must match
> @Bool(OR)
> @List({@Pattern(regexp="pat1"), at Pattern(regexp="pat2"), at Pattern(regexp="pat3"), at Pattern(regexp="pat4")})
> @interface WhiteList{..}
> {code}
> {code}
> //Specify that none of the patterns must match
> @Bool(ALLFALSE)
> @List({@Pattern(regexp="pat1"), at Pattern(regexp="pat2"), at Pattern(regexp="pat3"), at Pattern(regexp="pat4")})
> @interface BlackList{..}
> {code}
> {code}
> //At least on valid contact method must match
> @Bool(OR)
> @Email
> @Address
> @Phone
> @interface ContactDetails{...}
> {code}
> This would greatly increase the type of new constraints that can be defined just by reusing some existing ones.
> Possible extensions might be for example further operators like XOR (meaning exactly one of the constraints must hold) or similar.
> It seems like it is possible to implement this feature by adding very little code to just a couple of classes, and adding the new @Bool annotation to the API.

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