In Spring MVC it is possible to validate form fields using Bean Validation API (JSR 303 for Bean Vaidation 1.0 and JSR 349 for Bean Validation 1.1) that is used to define validation constraints of the JavaBean object.
Hibernate Validator is Bean Validation API reference implementation. Hibernate Validator offers additional value on top of the features required by Bean Validation. For example, a programmatic constraint configuration API as well as an annotation processor which plugs into the build process and raises compilation errors whenever constraint annotations are incorrectly used.