Pascal (Lazarus/Delphi)

Azure Blob - Get Tags (Check if Blob Exists)

See more Azure Cloud Storage Examples

Gets the user-defined tags for a specified blob. This can also be used as a way to check to see if a blob exists. Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.StringBuilder,
  Chilkat.Rest,
  Chilkat.AuthAzureStorage,
  Chilkat.Xml;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  rest: TRest;
  bTls: Boolean;
  port: Integer;
  bAutoReconnect: Boolean;
  azAuth: TAuthAzureStorage;
  sb: TStringBuilder;
  xml: TXml;

begin
  success := False;

  //  This example requires the Chilkat API to have been previously unlocked.
  //  See Global Unlock Sample for sample code.

  rest := TRest.Create;

  //  Connect to the Azure Storage Blob Service
  bTls := True;
  port := 443;
  bAutoReconnect := True;
  //  In this example, the storage account name is "chilkat".
  success := rest.Connect('chilkat.blob.core.windows.net',port,bTls,bAutoReconnect);
  if (success <> True) then
    begin
      WriteLn(rest.LastErrorText);
      Exit;
    end;

  //  Provide Azure Cloud credentials for the REST call.
  azAuth := TAuthAzureStorage.Create;
  azAuth.AccessKey := 'AZURE_ACCESS_KEY';
  //  The account name used here should match the 1st part of the domain passed in the call to Connect (above).
  azAuth.Account := 'chilkat';
  azAuth.Scheme := 'SharedKey';
  azAuth.Service := 'Blob';
  //  This causes the "x-ms-version: 2021-08-06" header to be automatically added.
  azAuth.XMsVersion := '2021-08-06';
  success := rest.SetAuthAzureStorage(azAuth);

  //  Note: The application does not need to explicitly set the following
  //  headers: Content-Length, x-ms-date, Authorization.  These headers
  //  are automatically set by Chilkat.

  //  The Azure blob container is "test", the file is "helloWorld.txt"
  //  Add "?comp=tags" to get the user-defined tags instead of the actual blob content.
  sb := TStringBuilder.Create;
  success := rest.FullRequestNoBodySb('GET','/test/helloWorldajdfadf.txt?comp=tags',sb);
  if (success = False) then
    begin
      //  Examine the request/response to see what happened.
      WriteLn('response status code = ' + rest.ResponseStatusCode);
      WriteLn('response status text = ' + rest.ResponseStatusText);
      WriteLn('response header: ' + rest.ResponseHeader);
      WriteLn('---');
      WriteLn('LastRequestStartLine: ' + rest.LastRequestStartLine);
      WriteLn('LastRequestHeader: ' + rest.LastRequestHeader);
      Exit;
    end;

  //  A typical blob with no tags will return this:

  //  <?xml version="1.0" encoding="utf-8"?>
  //  <Tags><TagSet/></Tags>

  //  If the blob does not exist, you get this:

  //  <?xml version="1.0" encoding="utf-8"?>
  //  <Error>
  //      <Code>BlobNotFound</Code>
  //      <Message>The specified blob does not exist.
  //  	RequestId:fcfefdd9-301e-001a-2135-3a23d2000000
  //  	Time:2023-02-06T14:17:00.7805577Z
  //      </Message>
  //  </Error>

  WriteLn(sb.GetAsString());

  //  To see if we got Tags or an Error, then examine the XML.
  xml := TXml.Create;
  xml.LoadSb(sb,True);

  //  Examine the tag..
  if (xml.TagEquals('Tags') = True) then
    begin
      WriteLn('Blob exists!');
    end
  else
    begin

      if (xml.ChildContentMatches('Code','BlobNotFound',True) = True) then
        begin
          WriteLn('Blob does not exist.');
        end
      else
        begin
          WriteLn('Some other error...');
        end;

    end;

  WriteLn('Success.');


  rest.Free;
  azAuth.Free;
  sb.Free;
  xml.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.