springMVC导出excel并提供下载

@Controller
public class PoiController {
    
    //返回一个ResponseEntity类型
    @RequestMapping("poidownloadtest.html")
    public ResponseEntity<byte[]> poiDownloadTest() throws UnsupportedEncodingException{
        //创建一个excel并写入测试内容
        HSSFWorkbook workbook=new HSSFWorkbook();
        HSSFSheet sheet=workbook.createSheet("downloadTestSheet");
        HSSFRow row=sheet.createRow(0);
        HSSFCell cell=row.createCell(0);
        cell.setCellValue("downTest");
　　　　 //创建结束

　　　　 //创建一个字节数组输出流对象
        ByteArrayOutputStream outputStream=new ByteArrayOutputStream();
        try {
　　　　　　  //将excel写入输出流
            workbook.write(outputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
        
        HttpHeaders headers=new HttpHeaders();
        String fileName=new String("downloadTest.xls".getBytes("UTF-8"),"iso-8859-1");
        headers.setContentDispositionFormData("attachment", fileName);
        headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
        
        ResponseEntity<byte[]> returnFile=new ResponseEntity<byte[]>
                            (outputStream.toByteArray(),headers,HttpStatus.CREATED);
        try {
            outputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return returnFile;
    }
}