Currently the used script language must be set using the lang attribute with each usage of the @ScriptAssert constraint. As often it makes sense to use one and the same language in all constraints of an application, it seems useful to provide a global configuration option for setting a default language:

Validator validator = Validation
    .byProvider( HibernateValidator.class )
    .configure()
    .defaultScriptAssertLanguage("ruby")
    .buildValidatorFactory()
    .getValidator();

The mandatory attribute ScriptAssert#lang)() would be required to have a default value, allowing to omit it when using the constraint.