I think I indeed understood you correctly and my answer is still the same
What's the problem because HttpServlet is an abstract class? Usually you make a class abstract if you have no reasonable or just a partly default implementation and you want to define the structure of a concrete class together with the methods a concrete class should implement.
Exactly this is the case with HttpServlet. There's no reasonable implementation for the service methods like doGet(), doPost() etc. because this of course depends on what your concrete servlet in your application should do! The doGet(), doPost() and all the other methods are just declared as a skeleton for concrete servlets because these methods are expected to be called from the servlet container like Tomcat.
Perhaps I misunderstood your question so just tell what's exactly the problem for you with the class HttpServlet being abstract.