[hibernate-issues] [Hibernate-JIRA] Commented: (HV-435) org.hibernate.validator.constraints.impl.PatternValidator rejecting empty strings

[Hardy Ferentschik (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HV-435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=39974#action_39974 ] 

Hardy Ferentschik commented on HV-435:
--------------------------------------

It is a border case. The reasoning behind the {{URL}} constraint implementation was that you can always use constraint composition ({{@NotNull}}, {{@NotEmpty}}, {{@URL}}). The BV spec in fact favors constraint composition (hence the recommendation to generally return {{true}} for {{null}}). Obviously the same argument could be made for {{@Pattern}}. 

The difference, however, is that {{@Pattern}} is part of the spec and the documentation does not mention the empty string as an exceptional case (only {{null}}). {{@URL}} is a Hibernate Validator specific constraint and we are more flexible to change the behavior. For a pattern an empty string seems also a valid input, since pattern can easily match the empty string. 

> org.hibernate.validator.constraints.impl.PatternValidator rejecting empty strings
> ---------------------------------------------------------------------------------
>
>                 Key: HV-435
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HV-435
>             Project: Hibernate Validator
>          Issue Type: Bug
>          Components: validators
>    Affects Versions: 4.1.0.Final
>         Environment: Hibernate Core 3.5.6 with MySql database (not relevant to this bug)
>            Reporter: Stephen Hiley
>   Original Estimate: 1h
>  Remaining Estimate: 1h
>
> The PatternValidator currently checks for a null value and returns true from isValid() in that case. An empty string should have the same effect. This is necessary for the same reason: to allow for an empty form submission (which commonly are submitted as empty strings rather than nulls) and only validate when some value is submitted. IMO, this should be standard behavior. If nothing else, provide an option to treat empty strings as ignored in the same manner that null values are treated today.
> Suggested modification:
> public boolean isValid(String value, ConstraintValidatorContext constraintValidatorContext) {
> 		if ( value == null || value.length() == 0) {
> 			return true;
> 		}
> Thanks,
> Stephen Hiley

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