@Override
    public void validate(FacesContext context, UIComponent component, Object value) throws ValidatorException {
        if (value == null) {
            return;
        }

        if (!pattern.matcher(value.toString()).matches()) {
            throw new ValidatorException(new FacesMessage(FacesMessage.SEVERITY_ERROR, "Validation Error",
                    value + " is not a valid email;"));
        }
    }
Custom Faces Validator for Email input
primefaces-showcase/src/main/java/org/primefaces/showcase/view/csv/EmailValidator.java