What methods I should ovveride in a servlet ?

For creating a website, create a HTTP servlet.

• Extend HttpServlet (an Abstract class)
• Override at least one method (usually one of the following) :
• doGet : to support HTTP GET requests
• doPost :  for HTTP POST requests
• doPut :  for HTTP PUT requests

Don't override service method, as it handles HTTP requests by dispatching them to handler methods for each type of HTTP request.