public void PPT(ActionEvent actionEvent) throws JRException, IOException{
init();
HttpServletResponse httpServletResponse=(HttpServletResponse)FacesContext.getCurrentInstance().getExternalContext().getResponse();
httpServletResponse.addHeader("Content-disposition", "attachment; filename=report.pptx");
ServletOutputStream servletOutputStream=httpServletResponse.getOutputStream();
JRPptxExporter docxExporter=new JRPptxExporter();
docxExporter.setParameter(JRExporterParameter.JASPER_PRINT, jasperPrint);
docxExporter.setParameter(JRExporterParameter.OUTPUT_STREAM, servletOutputStream);
docxExporter.exportReport();
}