Yes Abhishek, you instructor is right: it must be a unique servlets that acts like the controller. As you already heard Struts is a very popular (although far from being perfect) framework that could help you implementing an MVC paradigm. But I got the feeling this is only a training project and you won�t like using other frameworks.
From what I understood your architecture looks like this:
JSP1 -> Servlet1 -> EJB1
JSP2 -> Servlet2 -> EJB2
JSP3-> Servlet3 -> EJB3
Having a controller will make it look something like this:
JSP1 -> Controller Servlet -> Servlet1 -> EJB1
JSP2 -> Controller Servlet -> Servlet2 -> EJB2
JSP3 -> Controller Servlet -> Servlet3 -> EJB3
(Here the Controller Servlet is one and the same instance for every scenario). You might ask then why would you need the Servlet1, Servlet2 and Servlet3 anyway? Finally you might like changing your architecture like this:
JSP1 -> Controller Servlet -> EJB1
JSP2 -> Controller Servlet -> EJB2
JSP3 -> Controller Servlet -> EJB3
The ultimate challenge will be how to design the way your controller servlet locates the EJBs, invokes business methods and returns the result back to the clients. Having a huge servlet that implements all this logic is definitely something that you�d like to avoid. Finally you might consider developing your own framework of plain
java classes that do the job. You can develop and
test the framework independently of your struts controller, etc.