What is the difference between GenericServlet, HttpServlet and a Servlet?

Question

I was searching for exact difference between javax.servlet.http.HttpServlet , javax.servlet.GenericServlet and javax.Servlet unable to

Answer 1

1. Servlet interface
   Its the super interface for GenericServlet and HttpServlet. It contains 5 abstract methods and all inherited by GenericServlet and HttpServlet.
   • Problem
     If you want to create servlet by implementing Servlet interface all the 5 abstract methods of the interface Servlet should be overridden eventhough Programmer is not interested
   • Usage
     Only implement Servlet interface if you like to develop your own container.
2. GenericServlet
   Its the immediate subclass of Servlet interface and super class of HttpServlet. In this class, one abstract method exist: service(). Other 4 abstract methods are implemented in this class.
   • Problem
     All methods are concrete except service() method, So you have to implement it as a callback method.
   • Usage
     It is protocol independent so Can be used with any protocol like FTP, SMTP, HTTP etc.
3. HttpServlet
   Its subclass of both GenericServlet and Servlet interface. Immediate super class of HttpServlet is GenericServlet. HttpServlet does not contain any abstract method. Eventhough the HttpServlet does not contain any abstract methods, it is declared as abstract class by the Designers to not to allow the anyone to create an object directly because a Servlet object is created by the Servlet Container.
   • Problem
     HttpServlet is protocol dependent and used specific to HTTP protocol only.
   • Usage
     service() method need not be overridden. It can be replaced by doGet() or doPost() methods with the same parameters. Its most used method to create servlet.
     
     
     hierarchy
     Reference: way2java.com