文件上传下载前后端代码

以下是文件上传下载前后端代码的示例：

前端代码：

文件上传：

<template>
  <div>
    <input type="file" ref="file" @change="uploadFile"/>
  </div>
</template>

<script>
export default {
  methods: {
    uploadFile() {
      let file = this.$refs.file.files[0];
      let formData = new FormData();
      formData.append('file', file);
      axios.post('/upload', formData, {
        headers: {
          'Content-Type': 'multipart/form-data'
        }
      }).then(res => {
        console.log(res.data);
      }).catch(err => {
        console.log(err);
      });
    }
  }
}
</script>

文件下载：

<template>
  <div>
    <button @click="downloadFile">下载文件</button>
  </div>
</template>

<script>
export default {
 methods: {
    downloadFile() {
      axios({
        url: '/download',
        method: 'get',
        responseType: 'blob'
      }).then(res => {
        let blob = new Blob([res.data]);
        let downloadElement = document.createElement('a');
        let href = window.URL.createObjectURL(blob);
        downloadElement.href = href;
        downloadElement.download = 'file.txt';
        document.body.appendChild(downloadElement);
        downloadElement.click();
        document.body.removeChild(downloadElement);
        window.URL.revokeObjectURL(href);
      }).catch(err => {
        console.log(err);
      });
    }
  }
}
</script>

后端代码：

文件上传：

@PostMapping("/upload")
public String uploadFile(@RequestParam("file") MultipartFile file) {
    if (file.isEmpty()) {
        return "上传失败，请选择文件";
    }
    String fileName = file.getOriginalFilename();
    String filePath = "D:/upload/";
    File dest = new File(filePath + fileName);
    try {
        file.transferTo(dest);
        return "上传成功";
    } catch (IOException e) {
        e.printStackTrace();
    }
    return "上传失败！";
}

文件下载：

@GetMapping("/download")
public ResponseEntity<byte[]> downloadFile() throws IOException {
    String filePath = "D:/upload/";
    String fileName = "file.txt";
    File file = new File(filePath + fileName);
    HttpHeaders headers = new HttpHeaders();
    headers.setContentDispositionFormData("attachment", fileName);
    headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
    return new ResponseEntity<>(FileUtils.readFileToByteArray(file), headers, HttpStatus.CREATED);
}