附件下载：
后台接口返回文件流：

前端调取后台API接口：一定要注意写上： responseType: “blob”，否则下载后内容为乱码

export function downloadFile(query) {
  return request({
    url: "/assess/file/download",
    method: "get",
    params: query,
    **responseType: "blob"**
  });
}
```在vue 页面中引入api ,接口处理部分：

// 后台返回文件流转为blob,创建a标签，去下载
getdoen (index) {
  let urls = {
    url: index,
  }
  downloadFile(urls).then(response => {
    const fileName =index
    const bolb = new Blob([response], { type: '' })
    if ('download' in document.createElement('a')) {
      const link = document.createElement('a')
      link.download = fileName
      link.style.display = 'none'
      link.href = URL.createObjectURL(bolb)
      document.body.appendChild(link)
      link.click()
      URL.revokeObjectURL(link.href)
      document.body.removeChild(link)
    }
  });
},