*.do no sun-web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>TESTE</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <description></description>
    <display-name>ControleGeral</display-name>
    <servlet-name>ControleGeral</servlet-name>
    <servlet-class>br.com.guj.controle.ControleGeral</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ControleGeral</servlet-name>
    <url-pattern>*.do</url-pattern>
  </servlet-mapping>
</web-app>

package br.com.guj.controle;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class ControleGeraç
 */
public class ControleGeral extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    public ControleGeral() {
        super();
    }

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {		
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
	}

}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE sun-web-app PUBLIC "-//Sun Microsystems, Inc.//DTD GlassFish Application Server 3.0 Servlet 3.0//EN" "http://www.sun.com/software/appserver/dtds/sun-web-app_3_0-0.dtd">
<sun-web-app error-url="">
  <context-root>/3DImoveis</context-root>
  <class-loader delegate="true"/>
  <jsp-config>
    <property name="keepgenerated" value="true">
      <description>Keep a copy of the generated servlet class' java code.</description>
    </property>
  </jsp-config>
  
  <servlet>
    <servlet-name>FrontController</servlet-name>
    <principal-name>br.com.threedi.Controller.FrontController</principal-name>
  </servlet>
  
  <servlet-mapping>
    <servlet-name>FrontController</servlet-name>
    <url-pattern>*.do</url-pattern>
  </servlet-mapping>
  
  <session-config>
    <session-timeout>10</session-timeout>
  </session-config>
</sun-web-app>

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

package br.com.threedi.Controller;

import br.com.threedi.Utility.ExcessaoNegocio;
import br.com.threedi.Utility.RequestHelper;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.SQLException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 *
 * @author Thiaho Ventura NB
 */
@WebServlet(name="FrontController", urlPatterns={"/FrontController"})
public class FrontController extends HttpServlet {
   
   private static final long serialVersionUID = 1L;
    
   public FrontController(){
       super();
   } 
    
    /** 
     * Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {

        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();

        RequestDispatcher rd;
        String pagina = "erro.jsp";

        try {            

            RequestHelper helper = new RequestHelper(request);
            Command cmd = helper.getCommand();
            
            pagina = cmd.execute(request, response);
            
            rd = request.getRequestDispatcher(pagina);
            rd.forward(request, response);

        }
                
        catch(SQLException e){
            request.setAttribute("msgErro", e);
            pagina = "erro.jsp";
            rd = request.getRequestDispatcher(pagina);
            rd.forward(request, response);
        }
        
        catch(ExcessaoNegocio e){
            request.setAttribute("msgErro", e);
            
            if(!e.getPath().equals("")){
                pagina = e.getPath();
            }else{
                pagina = "erroNegocio.jsp";
            }

            rd = request.getRequestDispatcher(pagina);
            rd.forward(request, response);        
        }

        catch(Exception e){
            request.setAttribute("msgErro", e);
            pagina = "erro.jsp";
            rd = request.getRequestDispatcher(pagina);
            rd.forward(request, response);
        }

        finally {
            out.close();
        }
        
        

    } 

    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /** 
     * Handles the HTTP <code>GET</code> method.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        processRequest(request, response);
    } 

    /** 
     * Handles the HTTP <code>POST</code> method.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        processRequest(request, response);
    }

    /** 
     * Returns a short description of the servlet.
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>

}

<form action="cadastro.do" method="post">
            <input type="hidden" name="ac" id="ac" value="grvconta" />
            <div style="width:50%;">
            <fieldset>
                <legend>Cadastro de Usuário</legend>

...

protected void processRequest(HttpServletRequest request, HttpServletResponse response)  
    throws ServletException, IOException {  
	System.out.println("Chamou o Cadastro.do");