Django 连接腾讯云COS

最近在写 Desert 这个音游项目，为了不占用服务器带宽，我选择使用 COS 而不是存储在服务器本地。我的设计是不开放单独的上传接口，只让管理员登陆 Admin Site 手动创建数据库 record 并上传曲目文件。这么设计的话我们就需要使 Admin Site 的文件上传组件能被我们实现，然而这样很困难，而且不符合规范。

通过观察 model.FileField() 可以发现其中可传参数 storage。该参数实现了 Storage 类，描述了文件存储方式。

通过翻阅 Storage 类的代码，可以发现它需要实现若干方法。我们的需求也就是上传腾讯云COS仅需实现save()、url()、generate_filename()。库中源码如下：

def save(self, name, content, max_length=None):
  """
  Save new content to the file specified by name. The content should be
  a proper File object or any Python file-like object, ready to be read
  from the beginning.
  """
  # Get the proper name for the file, as it will actually be saved.
  if name is None:
    name = content.name
    if not hasattr(content, "chunks"):
      content = File(content, name)
      name = self.get_available_name(name, max_length=max_length)
      name = self._save(name, content)
      # Ensure that the name returned from the storage system is still valid.
      validate_file_name(name, allow_relative_path=True)
      return name
      
def generate_filename(self, filename):
  """
  Validate the filename by calling get_valid_name() and return a filename
  to be passed to the save() method.
  """
  filename = str(filename).replace("\\", "/")
  # `filename` may include a path as returned by FileField.upload_to.
  dirname, filename = os.path.split(filename)
  if ".." in pathlib.PurePath(dirname).parts:
    raise SuspiciousFileOperation(
      "Detected path traversal attempt in '%s'" % dirname
    )
  return os.path.normpath(os.path.join(dirname, self.get_valid_name(filename)))
    
  
  def url(self, name):
    """
    Return an absolute URL where the file's contents can be accessed
    directly by a web browser.
    """
    raise NotImplementedError("subclasses of Storage must provide a url() method")

在我们的需求中，save() 所做的是将文件上传到腾讯云 COS 上，generate_filename() 需要生成文件名，url() 则返回一个文件直链，供 302 跳转。实现代码如下：

secret_id = settings.COS_SECRET_ID # secret_id
secret_key = settings.COS_SECRET_KEY # secret_key
region = settings.REGION # bucket region
bucket = settings.BUCKET # bucket name
config = CosConfig(Region=region, Secret_id=secret_id, Secret_key=secret_key) # build a config
client = CosS3Client(config) # get a client object
host = 'https://' + bucket + '.cos.' + region + '.myqcloud.com/'
'''
以上的部分字段需自行写入 setting.py 中
'''


@deconstructible
class TencentStorage(Storage):
    def save(self, name, content, max_length=None):
        client.put_object(
            Bucket=bucket,
            Key='song/' + name,
            Body=content.read()
        )
        return name
      
    # 因为没有修改文件名的需求所以不实现，有需要的可以自行在这里构造字符串
    def generate_filename(self, filename):
      pass

    def url(self, name):
        file_url = client.get_object_url(bucket, 'song/' + name)
        return str(file_url)

有关腾讯云 COS SDK 的 API 使用可以自行阅读文档，这里不做解释。

实现好 Storage 后，只需传入 model.FileField 即可。

song_file = models.FileField(storage=TencentStorage(), null=True)

然后登陆 Admin Site，编辑对象即可上传。成品图：