The service method is the one responsible to call doGet, doPost, doPut, depending on the request type. In this case, it is just not calling these methods (but it's handling the requests anyway). Is it clear?
There is no Hard and fast rule to override service method if you extend HttpServlet.Since service method implementation is provided in HttpServlet class.Container will call this service method if you don't override it. Here there is logic which will call your doXxx() methods depending on its method type.If your overriding service method you are telling the container please call my service method rather than service method of HttpServlet class please correct me if i m wrong