Viwer export error "The response has already been committed"

Question

Hi,
When use export report button from CrystalReportViewer, always download a html file with error message "The response has already been committed".
Why does this issue occur, and how can it be resolved?
I make a servlet which invoke to processHttpRequest. This is the code where viewer si configurated:
          Object rptSrc = null;
          rptSrc = factoryPS.openReportSource(oInfoObject, Locale.ENGLISH);
             // use reportsource to initialize viewer
             CrystalReportViewer viewer = new CrystalReportViewer();
               try {
               viewer.setReportSource(rptSrc);
               } catch (ReportSDKExceptionBase e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
             // initialize display characteristics
             viewer.setDisplayPage(true);
             viewer.setDisplayGroupTree(true);
             viewer.setDisplayToolbar(true);
             viewer.setGroupTreeWidthUnit(CrHtmlUnitEnum.crHtmlUnitPixel);
             viewer.setGroupTreeWidth(125);
             viewer.setHasRefreshButton(true);
             viewer.setHasExportButton(true);
             viewer.setHasGotoPageButton(true);
             viewer.setHasLogo(false);
             viewer.setHasPageNavigationButtons(true);
             viewer.setHasPrintButton(false);
             viewer.setHasSearchButton(true);
             viewer.setHasToggleGroupTreeButton(true);
             viewer.setOwnPage(true);
             viewer.setName("CrystalReportViewer");
             viewer.setProductLocale(Locale.ENGLISH);
             viewer.setPrintMode(CrPrintMode.ACTIVEX);
                 viewer.processHttpRequest(request,response,
                                getServletConfig().getServletContext(),null);
          response.flushBuffer ();
             viewer.dispose();         
thanks in advance...

Answer 1

I have discovered my error.
To make proofs and show traces defined and use out object.
PrintWriter out = response.getWriter();
And this collision with viewer.processHttpRequest(request, response, context, null)
Thank you for your help.