delphi - 我希望能够将附件数据保存到我的 mysql 数据库中。我猜这意味着我必须将附件数据保存到 TStream 中

Question

我正在尝试使用 TBlobStream 方法将附件数据从 IMAP 服务器插入到 MySQL 数据库。

procedure TForm1.Button1Click(Sender: TObject);
var
  imap_message_count:Integer;
  current_record:Integer;
  imap_id:String;

  email_parts_count:Integer;
  current_email_part:Integer;


  attachment_stream:TStream;
  blob_stream:TStream;
  final_stream:TStream;

  attachment_data_set:TDataSet;
  attachment_data:TFDQuery;
  blob_field:TField;
begin
  IdIMAP41.Connect();
  if IdIMAP41.SelectMailBox('INBOX') then
  BEGIN
    imap_message_count := IdIMAP41.MailBox.TotalMsgs;
    for current_record := 1 to imap_message_count - 1 do
    begin
      IdIMAP41.GetUID(current_record, imap_id);
      IdIMAP41.UIDRetrieve(imap_id, IdMessage1);
      email_parts_count := IdMessage1.MessageParts.Count;
      for current_email_part := 1 to email_parts_count - 1 do
      begin
        if IdMessage1.MessageParts.Items[current_email_part] is TIdAttachment then
        begin
          attachment_stream := TIdAttachment(IdMessage1.MessageParts.Items[current_email_part]).OpenLoadStream;
          try
           AttachmentsTable.Insert;
           blob_field := AttachmentsTable.FieldByName('attachment');
            blob_stream := AttachmentsTable.CreateBlobStream(blob_field, bmWrite);
              try
                blob_stream.CopyFrom(attachment_stream, 0);
              finally
                AttachmentsTable.Post;
                blob_stream.Free;
              end;
           finally
            TIdAttachment(IdMessage1.MessageParts.Items[current_email_part]).CloseLoadStream;
           end;
        end;
      end;
    end;
  END;

end;

目前，我可以插入一个 ID，因为它是自动增量的，但是当我查看我的数据库附件字段时，我最终得到的结果为 Null。我的问题可能是什么？

我猜我没有正确访问我的 blob_stream 数据。

提前致谢

Answer 1

你走在正确的轨道上，但你做事的方式是错误的。

要访问附件的现有数据，请使用其OpenLoadStream()方法，例如:

var
  att_stream: TStream;

if IdMessage1.MessageParts.Items[current_email_part] is TIdAttachment then
begin
  att_stream := TIdAttachment(IdMessage1.MessageParts.Items[current_email_part]).OpenLoadStream();
  try
    // use att_stream data as needed, 
    // such as saving it to a DB... 
  finally
    TIdAttachment(IdMessage1.MessageParts.Items[current_email_part]).CloseLoadStream();
  end;
end;

PrepareTempStream() 用于将新数据保存到附件。 OpenLoadStream() 用于从附件中读取数据。