Delphi DLL

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. Delphi DLL

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, StringBuilder, Rest, AuthAzureStorage, Xml;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
rest: HCkRest;
bTls: Boolean;
port: Integer;
bAutoReconnect: Boolean;
azAuth: HCkAuthAzureStorage;
sb: HCkStringBuilder;
xml: HCkXml;

begin
success := False;

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

rest := CkRest_Create();

// Connect to the Azure Storage Blob Service
bTls := True;
port := 443;
bAutoReconnect := True;
// In this example, the storage account name is "chilkat".
success := CkRest_Connect(rest,'chilkat.blob.core.windows.net',port,bTls,bAutoReconnect);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    Exit;
  end;

// Provide Azure Cloud credentials for the REST call.
azAuth := CkAuthAzureStorage_Create();
CkAuthAzureStorage_putAccessKey(azAuth,'AZURE_ACCESS_KEY');
// The account name used here should match the 1st part of the domain passed in the call to Connect (above).
CkAuthAzureStorage_putAccount(azAuth,'chilkat');
CkAuthAzureStorage_putScheme(azAuth,'SharedKey');
CkAuthAzureStorage_putService(azAuth,'Blob');
// This causes the "x-ms-version: 2021-08-06" header to be automatically added.
CkAuthAzureStorage_putXMsVersion(azAuth,'2021-08-06');
success := CkRest_SetAuthAzureStorage(rest,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 := CkStringBuilder_Create();
success := CkRest_FullRequestNoBodySb(rest,'GET','/test/helloWorldajdfadf.txt?comp=tags',sb);
if (success = False) then
  begin
    // Examine the request/response to see what happened.
    Memo1.Lines.Add('response status code = ' + IntToStr(CkRest_getResponseStatusCode(rest)));
    Memo1.Lines.Add('response status text = ' + CkRest__responseStatusText(rest));
    Memo1.Lines.Add('response header: ' + CkRest__responseHeader(rest));
    Memo1.Lines.Add('---');
    Memo1.Lines.Add('LastRequestStartLine: ' + CkRest__lastRequestStartLine(rest));
    Memo1.Lines.Add('LastRequestHeader: ' + CkRest__lastRequestHeader(rest));
    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>

Memo1.Lines.Add(CkStringBuilder__getAsString(sb));

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

// Examine the tag..
if (CkXml_TagEquals(xml,'Tags') = True) then
  begin
    Memo1.Lines.Add('Blob exists!');
  end
else
  begin

    if (CkXml_ChildContentMatches(xml,'Code','BlobNotFound',True) = True) then
      begin
        Memo1.Lines.Add('Blob does not exist.');
      end
    else
      begin
        Memo1.Lines.Add('Some other error...');
      end;

  end;

Memo1.Lines.Add('Success.');

CkRest_Dispose(rest);
CkAuthAzureStorage_Dispose(azAuth);
CkStringBuilder_Dispose(sb);
CkXml_Dispose(xml);

end;