ReportClientDocument clientDoc = new ReportClientDocument();
clientDoc.open(reportPath,  0 );

IReportSource oReportSource = (IReportSource)clientDoc.getReportSource();

ExportOptions exportOptions = new ExportOptions();
exportOptions.setExportFormatType(ReportExportFormat.PDF);
        
        
ReportExportControl rex = new ReportExportControl();
        
rex.setReportSource(oReportSource);
rex.setExportOptions(exportOptions);
rex.setExportAsAttachment(true);

rex.processHttpRequest(request, response, request.getSession().getServletContext(), null);