java下载文件前后端代码_java 附件上传、下载前后端代码

以下是Java后端的代码：

文件上传：

@PostMapping("/upload")
public String upload(@RequestParam("file") MultipartFile multipartFile) {
    try {
        // 获取文件名
        String fileName = multipartFile.getOriginalFilename();
        // 获取文件的字节数组
        byte[] bytes = multipartFile.getBytes();
        // 设置文件存储路径
        Path path = Paths.get("uploads/" + fileName);
        // 将文件写入磁盘
        Files.write(path, bytes);
        return "上传成功";
    } catch (IOException e) {
        e.printStackTrace();
        return "上传失败";
    }
}

文件下载：

@GetMapping("/download")
public ResponseEntity<Resource> download(@RequestParam("fileName") String fileName) throws IOException {
    // 获取文件的路径
    Path path = Paths.get("uploads/" + fileName);
    // 从磁盘读取文件内容
    ByteArrayResource resource = new ByteArrayResource(Files.readAllBytes(path));
    // 构建响应头
    HttpHeaders headers = new HttpHeaders();
    headers.add(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=" + fileName);
    headers.add(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_OCTET_STREAM_VALUE);
    headers.add(HttpHeaders.CONTENT_LENGTH, String.valueOf(resource.contentLength()));
    // 返回响应
    return ResponseEntity.ok()
            .headers(headers)
            .body(resource);
}

以下是前端的代码：

文件上传：

<form method="post" action="/upload" enctype="multipart/form-data">
  <input type="file" name="file"/>
  <button type="submit">上传</button>
</form>

文件下载：

function download(fileName) {
  var xhr = new XMLHttpRequest();
  xhr.open('GET', '/download?fileName=' + fileName, true);
  xhr.responseType = 'blob';
  xhr.onload = function(e) {
    if (this.status == 200) {
      var blob = this.response;
      var link = document.createElement('a');
      link.href = window.URL.createObjectURL(blob);
      link.download = fileName;
      link.click();
    }
  };
  xhr.send();
}