Why GenericServlet has init() with no arg method?

Question

1)why GenericServlet has init() with no arg method also?.......when do we need this method, is there any such scenario?
2) why subclass of HttpServlet must override at least one DoXXX method and why we don't override service method? how does the server via "public service" method recognize to call the corresponding doXXX method like for get request call doGet() ?
Thanks in advance
Rahul

Answer 1

1) the javadocs explain exactly what the use of this method is. It's nothing more than a convenience method.
2) Technically you can override service() and ignore doGet() and doPost(). But that's just bad design, for all you know the service() method does more then just calling doGet() and doPost(). Do what the javadocs tell you, and they tell you to implement doGet() and/or doPost().
how does the server via "public service" method recognize to call the corresponding doXXX method like for get request call doGet()The answer is already in your question! The service() method checks the request method (get/post/put) and then calls the corresponding method in HttpServlet :s You can check this yourself, call HttpServletRequest.getMethod().