• 不用設置content-length，會自動設置
• 設置ContentDisposition，瀏覽器下載時的名字，中文的話不用url編碼也不會亂碼，ContentDisposition會根據(jù)傳入的Charsets.UTF_8自動編碼

    @RequestMapping("home")
    public ResponseEntity<byte[]> test() throws IOException {
        byte[] bytes = Files.asByteSource(new File("/Users/lfz/favicon.ico")).read();
        HttpHeaders headers=new HttpHeaders();
        //設置MIME類型
        headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
        headers.setContentDisposition(ContentDisposition.builder("attachment").filename("漢字.ico", Charsets.UTF_8).build());
        return new ResponseEntity<>(bytes, headers, HttpStatus.OK);
    }

     // 原封不動返回上傳的文件
    @PostMapping("/upload")
    public ResponseEntity<byte[]> upload(MultipartFile file) throws IOException {
        if (file.isEmpty()) {
            return ResponseEntity.ok().build();
        }
        HttpHeaders headers=new HttpHeaders();
        //設置MIME類型
        headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
        headers.setContentDisposition(ContentDisposition.builder("attachment").filename(StringUtils.isEmpty(file.getOriginalFilename()) ? "下載文件" : file.getOriginalFilename(), StandardCharsets.UTF_8).build());
        return new ResponseEntity<>(file.getBytes(), headers, HttpStatus.OK);
    }