/** 
 * This program is an example from the book "Internet 
 * programming with Java" by Svetlin Nakov. It is freeware. 
 * For more information: http://www.nakov.com/books/inetjava/ 
 */ 
import java.io.*; 
import javax.servlet.*; 
import javax.servlet.http.*; 
 
public class MainServlet extends HttpServlet { 
    public void doGet(HttpServletRequest aRequest, 
        HttpServletResponse aResponse) 
    throws IOException, ServletException { 
        HttpSession session = aRequest.getSession(); 
        String username = (String) session.getAttribute("USER"); 
        PrintWriter out = aResponse.getWriter(); 
        if (username == null) { 
            showMainForm("Not authenticated. Please " + 
                "<a href='login'>login</a> first.", out); 
        } else { 
            showMainForm("Welcome, " + username + "!", out); 
        } 
    } 
 
    private void showMainForm(String aText, PrintWriter aOut) { 
        aOut.println("<html>" + aText + "</html>"); 
    } 
}
Back to Internet Programming with Java books's web site