Applet Servlet Comm. Problem

Question

Dear friends,
i have an applet that sends a serialized object to the servlet,the Servlet creates another object and passes it back to the applet.
Everything works fine, till i read the object with:
ObjectInputStream objInputStream = new ObjectInputStream(in);
        show("got object input stream");
         chart = new ChartPanel((JFreeChart)objInputStream.readObject());At this point, i got nothing back.Instead i get a "null"returned on my Java Console.
From JBuilder it works fine
Here is the code
//This is called from the applet in order to load a chart in a panel
private JPanel getChartFromServlet(Object[] parameters) throws Throwable {
  ChartPanel chart=null;
  String server;
   try {
///////////////////////create URL Connection to SERVLET
    if (this.remoteServerMode) {
      this.show("http://10.30.1.38:8080/AppletToServlet/DbServlet");
       server="http://10.30.1.38:8080/AppletToServlet/DbServlet";
     else {
       server="http://localhost:8083/DbServlet";
     //SEND DATA TO SERVLET
     URLConnection servletCon=this.getServletConnection(server);
     // servletCon.setRequestProperty("Content-Type","application/octet-stream");
      //send the query parameters  using serialization
       ObjectOutputStream out=new ObjectOutputStream(servletCon.getOutputStream());
       out.writeObject( parameters);
       out.flush();
       out.close();
       this.show("Finish with send to servlet");
       //GET DATA FROM SERVLET
       InputStream in=servletCon.getInputStream();
       show("got input stream");
       ObjectInputStream objInputStream = new ObjectInputStream(in);
        show("got object input stream");
         chart = new ChartPanel((JFreeChart)objInputStream.readObject());
         show("got chart");
        objInputStream.close();
        in.close();
        chart.setPreferredSize(new Dimension(734, 370));
   catch (Exception ex) {
     System.err.println("Exception caught");
     this.show(ex.getMessage());
     this.show(ex.getMessage());
     System.err.println(ex.getMessage());
     ex.printStackTrace(System.err);
   throw new Exception( ex.getCause());
return chart;
//Servlet Side Code
public void doGet(HttpServletRequest request, HttpServletResponse response) throws
      ServletException, IOException {
    ObjectInputStream inputStreamFromApplet=null;
    Object[] queryParams;
  JFreeChart chart=null;
    try {
      response.setContentType("application/x-java-serialized-object");
      //////////////////////////READ INPUT//////////////////////////////////////
      InputStream in=request.getInputStream();
      inputStreamFromApplet=new ObjectInputStream(in);
      //Read applet's serialised object passed in Input Stream
      queryParams = (Object[]) inputStreamFromApplet.readObject();
      //do something with serialized object
      chart=getRequestedChart(queryParams);
      //////////////////////////WRITE OUTPUT////////////////////////////////////
      //open an output stream
      ObjectOutputStream out = new ObjectOutputStream(response.getOutputStream());
      //write to output stream
      out.writeObject(chart);
      out.flush();
      //close output stream
      out.close();
    catch (Exception ex) {
      ex.printStackTrace();
      System.err.println(ex.getMessage());
  }Do you have any ideas?
Apart from the null value,i saw also some SocketException
Is there a security issue involved?Both Servlet and Applet come from the same ip.
Thank you very much in advance,
Chris

Answer 1

A Chart constructor takes as an arg a JFreeChart.
Chart is a JComponent so i cannot serialize it.
That's why the servlet passes a JFreechart object and
the applet constructs a chart from it.
I cast the object to a jfreechart and pass it to the constructor of the chart.
The strange thing also is that, wghile initially with a non perfectly designed UI,everything worked fine but when i modified the applet's UI ,problems started...
Something with serialization and versions of classes?