SprigMvc文件下载

@RequestMapping(method = RequestMethod.GET ,value = "/down")
public ResponseEntity<byte[]>  DownLoad(HttpServletRequest request,String filename ){

    // 获取文件的真实路径
    String realPath = request.getServletContext().getRealPath("/WEB-INF/download/" + filename);
    HttpHeaders  httpHeaders ;
    byte[]  file ;
    try {
        InputStream inputStream=new FileInputStream(realPath);
        try {
           httpHeaders=new HttpHeaders();
            file  =new byte[inputStream.available()];
            inputStream.read(file);
             httpHeaders.add("Content-Disposition","attachment;filename="+filename);
            httpHeaders.setContentDispositionFormData("Content-Disposition",  URLEncoder.encode(filename, "utf-8"));
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    } catch (FileNotFoundException e) {
        throw new RuntimeException(e);
    }

    //需要传入的三个参数  文件名 文件的的字节读入数组 文件的请求头  文件的状态
    ResponseEntity<byte[]> responseEntity = new ResponseEntity<byte[]>(file, httpHeaders, HttpStatus.OK);
    return  responseEntity;

}