@@ -0,0 +1,299 @@
+package at.ac.tuwien.inso.service.validator;%0A%0Aimport at.ac.tuwien.inso.exception.ValidationException;%0A%0Apublic class SubjectValidator %7B%0A%0A    public void validateSubjectId(Long id) %7B%0A        if(id == null %7C%7C id %3C 1) %7B%0A            throw new ValidationException(%22Subject invalid id%22);%0A        %7D%0A    %7D%0A%7D%0A

add a subject validator