Colocar arquivo para download

public static void imprimir(List<Relatorio> lista, String reportUrl, Map<String, Object> parametros){
		FacesContext facesContext = FacesContext.getCurrentInstance();
		
		HttpServletRequest request = (HttpServletRequest) facesContext.getExternalContext().getRequest();
		HttpServletResponse response = (HttpServletResponse) facesContext.getExternalContext().getResponse();
		OutputStream os = null;
		
		try {
			String reportUrlReal = request.getSession().getServletContext().getRealPath("relatorio" + File.separator + reportUrl);
			
			JRBeanCollectionDataSource ds = new JRBeanCollectionDataSource(lista);
			JasperPrint jasperPrint = JasperFillManager.fillReport(reportUrlReal, parametros, ds);
			byte[] pdf = JasperExportManager.exportReportToPdf(jasperPrint);
			
			os = response.getOutputStream();
			response.setContentType("application/pdf");
			response.setContentLength(pdf.length);
			response.setHeader("Content-disposition","attachment; filename=\""+ reportUrl.substring(0, reportUrl.length() - 7)+ ".pdf\"");
			os.write(pdf);
		} catch (Exception e) {
			e.printStackTrace();
		} finally{
			try {
				if(os != null){
					os.flush();
					os.close();
				}
				facesContext.responseComplete();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}