(Delphi ActiveX) OneDrive -- Streaming REST Download to File

Downloads the contents of a DriveItem directly to a file in the local filesystem using the Chilkat REST class.

Note: This example requires Chilkat v9.5.0.69 or greater.

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_v9_5_0_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
rest: TChilkatRest;
success: Integer;
oauth2: TChilkatOAuth2;
uriPath: WideString;
statusCode: Integer;
discard: TChilkatBinData;
redirectUrl: IChilkatUrl;
sbJson: TChilkatStringBuilder;
jsonErr: TChilkatJsonObject;
localPath: WideString;
stream: TChilkatStream;

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

rest := TChilkatRest.Create(Self);

// Use your previously obtained access token here:
// See the following examples for getting an access token:
//    Get Microsoft Graph OAuth2 Access Token (Azure AD v2.0 Endpoint).
//    Get Microsoft Graph OAuth2 Access Token (Azure AD Endpoint).
//    Refresh Access Token (Azure AD v2.0 Endpoint).
//    Refresh Access Token (Azure AD Endpoint).

// First connect to graph.microsoft.com.  If there's a connectivity problem, we'll find out here.
success := rest.Connect('graph.microsoft.com',443,1,1);
if (success <> 1) then
  begin
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;

// (Make sure your token was obtained with the FilesRead or Files.ReadWrite scope.)
oauth2 := TChilkatOAuth2.Create(Self);
oauth2.AccessToken := 'MICROSOFT_GRAPH_ACCESS_TOKEN';
rest.SetAuthOAuth2(oauth2.ControlInterface);

// Send the GET request to download the file.
uriPath := '/v1.0/me/drive/root:/Misc/wildlife/penguins.jpg:/content';
success := rest.SendReqNoBody('GET',uriPath);
if (rest.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;

// NOTE: This way of doing the HTTP GET (i.e. download) may be more cumbersome, but it 
// allows for finer control of handling errors.  The connection establishment, the sending of the
// request, the reading of the response header, and the reading of the response body (i.e. the file data)
// are handled by separate method calls.  If the response header indicates an error, we can read
// the response body and treat it differently than if reading the file data.

// Read the response header.
statusCode := rest.ReadResponseHeader();
Memo1.Lines.Add('Response Status Code = ' + IntToStr(statusCode));
if (statusCode = 302) then
  begin
    // This is a redirect.  Read the response body, if any, and then follow the redirect.
    // Usually the response body will be empty for a redirect, but we need to be sure to read
    // the response body just in case it exists.
    discard := TChilkatBinData.Create(Self);
    rest.ReadRespBd(discard.ControlInterface);
    rest.Disconnect(10);

    // For OneDrive, the redirect URL does not need authorization because the only way
    // to have obtained the direct download URL is from an authenticated request.
    // In fact, if we leave the authentication present, the GET request to the redirect URL will fail.

    // Note: The ClearAuth method is introduced in v9.5.0.69.
    rest.ClearAuth();

    // Follow the redirect URL...
    redirectUrl := rest.RedirectUrl();
    Memo1.Lines.Add('Redirect Host: ' + redirectUrl.Host);
    Memo1.Lines.Add('Redirect URI Path: ' + redirectUrl.PathWithQueryParams);

    success := rest.Connect(redirectUrl.Host,redirectUrl.Port,redirectUrl.Ssl,1);
    if (success <> 1) then
      begin
        Memo1.Lines.Add(rest.LastErrorText);
        Exit;
      end;

    // Send the request..
    success := rest.SendReqNoBody('GET',redirectUrl.Path);

    if (rest.LastMethodSuccess <> 1) then
      begin
        Memo1.Lines.Add(rest.LastErrorText);
        Exit;
      end;

    statusCode := rest.ReadResponseHeader();
    Memo1.Lines.Add(rest.LastErrorText);
    Memo1.Lines.Add('Redirect Response Status Code = ' + IntToStr(statusCode));

  end;

if (statusCode >= 300) then
  begin

    // Read the error response body.
    sbJson := TChilkatStringBuilder.Create(Self);
    success := rest.ReadRespSb(sbJson.ControlInterface);
    if (success <> 1) then
      begin
        Memo1.Lines.Add(rest.LastErrorText);
        Exit;
      end;

    jsonErr := TChilkatJsonObject.Create(Self);
    jsonErr.EmitCompact := 0;
    jsonErr.LoadSb(sbJson.ControlInterface);
    Memo1.Lines.Add(jsonErr.Emit());

    Exit;
  end;

// Stream the response body directly to a local file.
localPath := 'qa_output/penguins.jpg';

stream := TChilkatStream.Create(Self);
stream.SinkFile := localPath;

success := rest.ReadRespBodyStream(stream.ControlInterface,1);
if (success <> 1) then
  begin
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('Successfully streamed a OneDrive file to the local filesystem.');
end;