XML Validation vs Java validation

I'm using hibernate validation and am debating which would be a better form of validation for legacy Pojos. Hibernate allows for validation through XML http://docs.jboss.org/hibernate/validator/4.2/reference/en-US/html/validator-xmlconfiguration.html The new ones can be annotated with constraints which is easier to read. However, for older / generated code that cannot be annotated, putting it in