[PROPOSAL] New annotation for nullable @NotBlank / @NotEmpty validation

I've noticed an inconsistency in the default behavior of the constraint API. With the exception of @Null, almost all constraints in the jakarta.validation.constraints package consider a null value as valid. This is a well-documented and generally useful behavior, as it allows developers to handle optional fields by combining constraints with @NotNull only when required.

However, the @NotEmpty and @NotBlank constraints are notable exceptions to this rule. They explicitly fail on null values.

This creates an inconvenience when validating optional fields. For example, if I have an optional string field that should be non-blank if it's present, there is no clear and declarative way to express this.

The cleanest workaround is creating a custom constraint, which adds boilerplate and complexity for a seemingly common use case.

I understand that changing the default behavior of @NotBlank and @NotEmpty would be a massive breaking change and is not feasible for backward compatibility reasons.

Therefore, I would like to propose the introduction of a new annotation, for example:

• @NotBlankOrNull
• @NotBlankIfPresent

This new annotation would validate that a string is not blank only if it is present (i.e., not null). A null value would be considered valid. This would bring the behavior in line with other constraints, providing a consistent and declarative way to validate optional, non-blank strings.

If this is better suited for incubation in a specific provider (like Hibernate Validator) first, please let me know, and I would be happy to open an issue there instead.

Thank you for your time and consideration.

Start by reviewing the Jakarta Validation constraint API and the existing @NotBlank and @NotEmpty semantics described in the issue. Determine whether a new nullable non-blank constraint belongs in the specification or should incubate in a provider such as Hibernate Validator; agreement on the annotation and its behavior would define done.