Head First Servlet and JSP - MVC download JAR example

Hi all,
I am studying from Head First Servlet and JSP...which I consider the best book ever about programmig, I am doing all the examples...but now I have a problem:
I have followed the whole tutorial about MVC in chapter 3, at page 129 (chapter 4) there is an example of a servlet used to download a JAR file; I wrote a simple MVC application that uses the code in the book.
These are the files I wrote:
form.html

RetrieveJAR.java

/**
 * Controller
 */
package com.example.controller;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
 
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
import com.example.model.Utilities;
 
public class RetrieveJAR extends HttpServlet {
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("application/jar");        
        String fileName = "/" + request.getParameter("fileName");
        Utilities util = new Utilities();
        ServletContext ctx = getServletContext();
        InputStream is = ctx.getResourceAsStream(fileName);
        OutputStream os = response.getOutputStream();        
        String result = util.streamToStream(is, os, 1024);       
        request.setAttribute("result", result);
        RequestDispatcher view = request.getRequestDispatcher("result.jsp");
        view.forward(request, response);
    }
}

Utilities.java

result.jsp

web.xml

If the file exists the user can download it, but if it doesn't exists the web app crashes...I would like the result.jsp to show the user the "result" string returned by the Model Utilities.java.

Is this architecture a good MVC implementation?
Is this a "real world" example?

Thank you for your time.
Giovanni