public CustomerSpecifications { public static Specification<Customer> customerHasBirthday() { return new Specification<Customer> { public Predicate toPredicate(Root<T> root, CriteriaQuery query, CriteriaBuilder cb) { return cb.equal(root.get(Customer_.birthday), today); } }; } public static Specification<Customer> isLongTermCustomer() { return new Specification<Customer> { public Predicate toPredicate(Root<T> root, CriteriaQuery query, CriteriaBuilder cb) { return cb.lessThan(root.get(Customer_.createdAt), new LocalDate.minusYears(2)); } }; } }

Okay I finally found an example: https://github.com/gothinkster/kotlin-spring-realworld-example-app/blob/master/src/main/kotlin/io/realworld/repository/specification/ArticlesSpecifications.kt

Thanks for your help anyway