springboot实现返回文件流

@GetMapping (value = "/file/{fileName}" )

public ResponseEntity<FileSystemResource> getFile( @PathVariable ( "fileName" ) String fileName) throws FileNotFoundException {

     File file = new File(filePath, fileName);

     if (file.exists()) {

         return export(file);

     }

     System.out.println(file);

     return null ;

}

public ResponseEntity<FileSystemResource> export(File file) {

     if (file == null ) {

         return null ;

     }

     HttpHeaders headers = new HttpHeaders();

     headers.add( "Cache-Control" , "no-cache, no-store, must-revalidate" );

     headers.add( "Content-Disposition" , "attachment; filename=" + file.getName());

     headers.add( "Pragma" , "no-cache" );

     headers.add( "Expires" , "0" );

     headers.add( "Last-Modified" , new Date().toString());

     headers.add( "ETag" , String.valueOf(System.currentTimeMillis()));

     return ResponseEntity.ok().headers(headers).contentLength(file.length()).contentType(MediaType.parseMediaType( "application/octet-stream" )).body( new FileSystemResource(file));

}

@GetMapping ( "/getTemplateFile" )

@ApiOperation ( "数据模板下载" )

public ResponseEntity< byte []> downFile(HttpServletRequest request) throws IOException {

     File file = new File( "C/AA" );

     filename = getFilename(request, filename);

     //设置响应头

     HttpHeaders headers = new HttpHeaders();

     //通知浏览器以下载的方式打开文件

     headers.setContentDispositionFormData( "attachment" , filename);

     //定义以流的形式下载返回文件数据

     headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);

     //使用springmvc框架的ResponseEntity对象封装返回数据

     return new ResponseEntity<>(FileUtils.readFileToByteArray(file), headers, HttpStatus.OK);

}

/**

  * 根据浏览器的不同进行编码设置

  *

  * @param request  请求对象

  * @param filename 需要转码的文件名

  * @return 返回编码后的文件名

  * @throws IOException

  */

public String getFilename(HttpServletRequest request, String filename) throws IOException {

     //IE不同版本User-Agent中出现的关键词

     String[] IEBrowserKeyWords = { "MSIE" , "Trident" , "Edge" };

     //获取请求头代理信息

     String userAgent = request.getHeader( "User-Agent" );

     for (String keyWord : IEBrowserKeyWords) {

         if (userAgent.contains(keyWord)) {

             //IE内核浏览器，统一为utf-8编码显示

             return URLEncoder.encode(filename, "UTF-8" );

         }

     }

     //火狐等其他浏览器统一为ISO-8859-1编码显示

     return new String(filename.getBytes(StandardCharsets.UTF_8), StandardCharsets.ISO_8859_1);

}