Problemas com aplicação WEB (JSP e Tomcat)

package loja;
import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class Controller extends HttpServlet {

  // initialise the stock bean
  // note that it is done from the controller not a JSP
  public void init(ServletConfig config) throws ServletException {
    super.init(config);
    ServletContext application = getServletContext();
    application.setAttribute("stock",new Stock());
  }

  // this is where is the controller allocates the appropriate redirection
  public void doGet(HttpServletRequest req, HttpServletResponse res)
            throws ServletException, IOException {
    ServletContext application = getServletContext();
    
    if (req.getParameter("page") != null) {
        boolean browsing = (req.getParameter("browsing")) != null;
        String page = req.getParameter("page");
        String nextURL = "";
        // the logic here could be factored out
        // into separate request handler classes
        if (page.equals("book") )
            nextURL="/book.jsp";
        else if (page.equals("cd"))
            nextURL="/cd.jsp";
        else if (page.equals("dvd"))
            nextURL="/dvd.jsp";
        else
            nextURL="/errorPage.jsp";

        // now forward the request to the appropriate page
        RequestDispatcher dispatcher = application.getRequestDispatcher(nextURL);
        dispatcher.forward(req,res);
    }
    else {
        RequestDispatcher dispatcher = application.getRequestDispatcher("/welcome.jsp");
        dispatcher.forward(req,res);
    }
  }
}

<FORM name="form1" method="get" ACTION="controller?page=/PAGINA_DE_DESTINO.jsp">

<form name="form1" method="get" action="controller?page=/PAGINA_DE_DESTINO.jsp">

<servlet-mapping>

		<servlet-name>Controller</servlet-name>

		  <url-pattern>/controller</url-pattern>

</servlet-mapping>