Customizing Validator Messages
Bean Validation includes a resource bundle of default messages for the built-in constraints. These messages can be customized, and localized for non-English speaking locales.
The ValidationMessages Resource Bundle
The Validationmessages resource bundle and the locale variants of this resource bundle contain strings that override the default validation messages. The ValidationMessages resource bundle is typically a properties file, ValidationMessages.properties, in the default package of an application.
Localizing Validation Messages
Locale variants of ValidationMessages.properties are added by appending an underscore and the locale prefix to the base name of the file. For example, the Spanish locale variant resource bundle would be ValidationMessages_es.properties.