Manter formato relatorio ao exportar excel

public String executarExcel(HttpServletResponse response) {
		JasperPrint impressao;
		try {
			con = this.getConexao();

			impressao = JasperFillManager.fillReport(relatorio, hash, con);

			byte bytes[] = new byte[10];
			JRXlsExporter exporter = new JRXlsExporter();

			ByteArrayOutputStream xlsReport = new ByteArrayOutputStream();
			exporter.setParameter(JRExporterParameter.JASPER_PRINT, impressao);
			exporter.setParameter(JRExporterParameter.OUTPUT_STREAM, xlsReport);
			exporter.setParameter(JRExporterParameter.OUTPUT_FILE, url
					+ "\\relatorios\\");
			exporter.setParameter(JRExporterParameter.OUTPUT_FILE_NAME,
					nomeArquivo + ".xls");
			exporter.exportReport();
			System.out.println("Sixe of byte array:" + xlsReport.size());
			bytes = xlsReport.toByteArray();
			response.setContentType("application/vnd.ms-excel");
			response.setContentLength(bytes.length);
			xlsReport.close();
			OutputStream ouputStream = response.getOutputStream();
			ouputStream.write(bytes, 0, bytes.length);
			ouputStream.flush();
			ouputStream.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
		return "/" + this.nomeArquivo;

	}