In addition to built-in converters and validators, JSF supports creating custom converters and validators. We can also extend the PrimeFaces CSV framework to support custom converters and validators, and perform conversions and validations on the client side, similar to the built-in converters and validators.
To create a custom JSF validator, we need to implement
javax.faces.validator.Validator. To make this custom validator work with the PrimeFaces CSV framework, we also need to implement the
org.primefaces.validate.ClientValidator interface to provide a client validator ID and validation metadata.