Exception invalid stream header: 74000346

[Ricardo Prado]

Hello people.

Well, I'm having a problem ( https://coderanch.com/t/512605/Servlets/java/Why-servlet-not-answering-when ) and the way that I've found to solve it is a little bit (a lot actually) bizarre.

To keep my connection alive, I'm sending a message every 0.5 seconds to the servlet to stop him from closing the connection. (IF YOU KNOW HOW TO CONFIGURE HOW LONG AN APPLICATION WAITS FOR AN HTTP ANSWER, PLEASE TELL ME SO I DON'T HAVE TO MAKE THIS EXTREMELY BIZARRE SOLUTION!)

The problem is that I'm getting an invalid stream header. I think that I'm writing two things at the same time(messing up my object).

Well, I'll post my code here, please don't try to kill me. I would LOVE to hear constructive critics(is that right? I want to mean is "I know that it is bizarre, but when you comply please tell me how to make it better")

Thanks!

   /*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package br.ceptro.simet.analyzer.servlet;

import br.ceptro.simet.analyzer.applet.ObjetoSolicitacao;
import br.ceptro.simet.analyzer.graph.GeradorDeGraficos;
import br.ceptro.simet.analyzer.util.MensageiroAuxiliarDoServletQueEnviaObjetos;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
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.swing.Timer;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.plot.PiePlot;
import org.jfree.chart.plot.Plot;

/**
 *
 * @author ricardo
 */
@WebServlet(name = "EnviadorDeObjetosChartServlet", urlPatterns = {"/EnviadorDeObjetosChartServlet"})
public class EnviadorDeObjetosChartServlet extends HttpServlet {


    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        final MensageiroAuxiliarDoServletQueEnviaObjetos mensageiro = new MensageiroAuxiliarDoServletQueEnviaObjetos();
      
        response.setContentType("application/x-java-serialized-object");

        OutputStream out = response.getOutputStream();
        final ObjectOutputStream objectOut = new ObjectOutputStream(out);

        InputStream in = request.getInputStream();
        ObjectInputStream objectIn = new ObjectInputStream(in);
        try {
            ObjetoSolicitacao objetoSolicitacao = (ObjetoSolicitacao) objectIn.readObject();
   
            GeradorDeGraficos gerador = new GeradorDeGraficos();
            List<String> operadoras = objetoSolicitacao.getOperadoras();
            long inicio = obterMilis(objetoSolicitacao.getInicio());
            long fim = obterMilis(objetoSolicitacao.getFim());
            objectOut.writeObject("Aguarde");
            objectOut.writeObject("FIM");
            //UNTIL HERE IT IS OK!
            // Here I'll create a new thread to send the messages (it is below)
// I think(95% sure) that is here where the problem happens
            criarUmaThreadParaEnviarAsMensagens(objectOut, mensageiro);
            
            JFreeChart chart = gerador.gerarGraficoGeral(operadoras, inicio, fim, -1, -1);

            mensageiro.setStatus("Fim");
            escrever(chart, objectOut);

            objectOut.flush();


        } catch (Exception ex) {
            mensageiro.setStatus("EXCEPTION");
            ex.printStackTrace();
        } finally {
            objectOut.close();
            out.flush();
            out.close();
            in.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>

    private long obterMilis(String inicio) {
        SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yy");
        Date d = null;
        try {
            d = sdf.parse(inicio);
        } catch (ParseException ex) {
            d = new Date();
        }
        return d.getTime();
    }

    private synchronized void escrever(Object mensagem, ObjectOutputStream objectOut) throws IOException {
                    objectOut.writeObject(mensagem);
    }

    private void criarUmaThreadParaEnviarAsMensagens(final ObjectOutputStream objectOut, final MensageiroAuxiliarDoServletQueEnviaObjetos mensageiro) {

        Thread r = new Thread(new Runnable() {

            public void run() {
                Timer timer = new Timer(500, new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent ae) {
                        try {
                            escrever(mensageiro.getStatus(), objectOut);

                        } catch (IOException ex) {
                            Logger.getLogger(EnviadorDeObjetosChartServlet.class.getName()).log(Level.SEVERE, null, ex);
                        }
                    }


                });
                timer.start();

                if (mensageiro.getStatus().equals("FIM") || mensageiro.getStatus().equals("EXCEPTION")) {
                    timer.stop();
                    timer = null;
                    System.gc();
                    
                }
            }
        });
        r.start();
    }
}
 

[Joe Ess]

Let's keep the discussion in one topic. I'm locking this one.