JSR303 custom validators being called twice

You can just add this property in your application.property files to disable hibernate validation spring.jpa.properties.javax.persistence.validation.mode=none

Maybe the second validation is done by hibernate when you are sending your bean to the datastore. To turn it off add this to your persistence.xml:

<property name="javax.persistence.validation.mode" value="none"/>

https://docs.jboss.org/hibernate/entitymanager/3.5/reference/en/html/configuration.html says:

By default, Bean Validation (and Hibernate Validator) is activated. When an entity is created, updated (and optionally deleted), it is validated before being sent to the database. The database schema generated by Hibernate also reflects the constraints declared on the entity.

You can fine-tune that if needed:

AUTO: if Bean Validation is present in the classpath, CALLBACK and DDL are activated.

CALLBACK: entities are validated on creation, update and deletion. If no Bean Validation provider is present, an exception is raised at initialization time.

DDL: (not standard, see below) database schemas are entities are validated on creation, update and deletion. If no Bean Validation provider is present, an exception is raised at initialization time.

NONE: Bean Validation is not used at all

The first one is obviously done by your Spring controller because of @Valid annotation.