Calculadora jsp em mvc

Front-end
#1

Boa tarde galera,
to precisando de uma ajuda… tenho está calculadora abaixa em java web.
Não estou conseguindo retornar o valor inteiro para a jsp.
podem me dizer como faço isso?
obrigado.

Pagina da servlet…

[code]/*

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

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;
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;
import javax.servlet.http.HttpSession;
import modelo.vo_calculadora;

@WebServlet(name = “sv_calculadora”, urlPatterns = {"/sv_calculadora"})
public class sv_calculadora extends HttpServlet {

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException, SQLException {
    response.setContentType("text/html;charset=UTF-8");
    PrintWriter out = response.getWriter();

  //HttpSession sessao = request.getSession(true);
  String opcao = request.getParameter("act");

  vo_calculadora obj_calc_vo = new vo_calculadora();

 // dao_calculadora obj_calc_dao = new dao_calculadora();

        String num1 = request.getParameter("n1");
        String num2 = request.getParameter("n2");
        //String resultado = request.getParameter("");

        int result;
    if (opcao.equals("soma")) {

      int n1 = Integer.parseInt(num1);
      int n2 = Integer.parseInt(num2);
      //int result = Integer.parseInt(resultado);
       
        obj_calc_vo.setValor1(n1);
        obj_calc_vo.setValor2(n2);

        result = n1 + n2;
       // out.println(result);
        request.setAttribute("result", result);
       
        RequestDispatcher rd = request.getRequestDispatcher("index.jsp");
        rd.forward(request, response);
    }

}

// <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 {
    try {
        processRequest(request, response);
    } catch (SQLException ex) {
        Logger.getLogger(sv_calculadora.class.getName()).log(Level.SEVERE, null, ex);
    }
}

/** 
 * 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 {
    try {
        processRequest(request, response);
    } catch (SQLException ex) {
        Logger.getLogger(sv_calculadora.class.getName()).log(Level.SEVERE, null, ex);
    }
}

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

}

pagina da jsp
[/code]

<%@page import=“javax.naming.spi.DirStateFactory.Result”%>
<%@page import=“modelo.vo_calculadora”%>

<%@page import=“java.util.List”%>
<%@taglib prefix=“sql” uri=“http://java.sun.com/jsp/jstl/sql”%>
<%@page contentType=“text/html” pageEncoding=“ISO-8859-1”%>

Calculadora 
<form action="/calculadora/sv_calculadora" method="post">
        <p>1° Número:
            <input type="text" name="n1"></p>

        <p>2° Número:
            <input type="text" name="n2"></p>

        
        <p>
            <input type="radio" name="act" value="soma"> Soma<br>
            <input type="radio" name="act" value="subtrai"> Subtração<br>
            <input type="radio" name="act" value="divide"> Divisão<br>
            <input type="radio" name="act" value="multiplica"> Multiplicação<br>
        </p>
        <p><input type="submit" value="calcular"></p>

        <h3>Resultado: </h3>
	<%

            //String num2 = request.getParameter("result");
            //int n1 = Integer.parseInt(num1);
                
                String result = (String) request.getParameter("result");
                
                int resultado = Integer.parseInt(result);
                
                System.out.print(resultado);         //if (session.getAttribute("obj_calc_vo") != null) {
                        //vo_calculadora obj_calc_vo = (vo_calculadora) session.getAttribute("obj_calc_vo");
        %>
    </form>

Erro que esta dando

HTTP Status 500 -

type Exception report

message

descriptionThe server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: java.lang.NumberFormatException: null
root cause

java.lang.NumberFormatException: null
note The full stack traces of the exception and its root causes are available in the GlassFish Server Open Source Edition 3.0.1 logs.

GlassFish Server Open Source Edition 3.0.1

#2

OK, já consegui resolver o problema… eu tinha que transformar o valor inteiro do resultado da soma para String novamente para pode retornar para a servlet.

#3