使用INDY检测远程服务器上文件的MIME类型 [英] Detecting the Mime-Type of a file on a remote server with INDY

问题描述

我一直在使用Synapse库从互联网上下载文件，但是最近我将应用程序转换为使用INDY，而我却错过了Synapse库中更好的功能之一，即可以轻松获取Mime的功能. -在将文件保存到本地计算机之前从服务器下载的文件的类型. INDY是否具有此功能，如果可以，我该如何访问它?

I have been using the Synapse library to download files from the internet, but I have recently converted my application to use INDY instead and I am missing one of the nicer features in the Synapse library which is the ability to easily get the Mime-Type of a file that I was downloading from a server before saving it to my local machine. Does INDY have this feature and if so how do I go about accessing it?

推荐答案

您可以发出HTTP HEAD请求并检查Content-Type标头.实际GET文件(下载)之前:

You can issue an HTTP HEAD request and check the Content-Type header. Before you actually GET the file (download) :

procedure TForm1.Button1Click(Sender: TObject);
var
  Url: string;
  Http: TIdHTTP;
begin
  Url := 'http://yoursite.com/yourfile.png';
  Http := TIdHTTP.Create(nil);
  try
    Http.Head(Url);
    ShowMessage(Http.Response.ContentType); // "image/png"
  finally
    Http.Free;
  end;
end;

您收到的ContentType取决于Web服务器的实现，并且不能保证每台服务器上的ContentType都相同.

The ContentType you receive back depends on the web server implementation and is not guaranteed to be the same on each and every server.

另一种选择是实际GET文件并将其内容保存到诸如TMemoryStream之类的内存流中(而不是保存到本地文件中). Indy提供了重载:

The other option, is to actually GET the file and save it's content to a memory stream such as TMemoryStream (not to a local file). Indy provides an overload:

Http.Get(Url, AStream);

然后您检查Http.Response.ContentType，并将流保存到文件:AStream.SaveToFile.

Then you check the Http.Response.ContentType, and Save the stream to file: AStream.SaveToFile.

不确定此处的相关性，但还要注意，Indy也可以返回/猜测本地文件的mime类型(给定文件扩展名).使用GetMIMETypeFromFile(使用IdGlobalProtocols).另请参见此处.

Not sure about the relevancy here, but note also that Indy can return/guess the mime type of a local file as well (given a file extension). with GetMIMETypeFromFile (uses IdGlobalProtocols). See also here.

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