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

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Url, JsonObject, OAuth2, StringBuilder, BinData, Stream, Rest;

...

procedure TForm1.Button1Click(Sender: TObject);
var
rest: HCkRest;
success: Boolean;
oauth2: HCkOAuth2;
uriPath: PWideChar;
statusCode: Integer;
discard: HCkBinData;
redirectUrl: HCkUrl;
sbJson: HCkStringBuilder;
jsonErr: HCkJsonObject;
localPath: PWideChar;
stream: HCkStream;

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

rest := CkRest_Create();

// 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 := CkRest_Connect(rest,'graph.microsoft.com',443,True,True);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    Exit;
  end;

// (Make sure your token was obtained with the FilesRead or Files.ReadWrite scope.)
oauth2 := CkOAuth2_Create();
CkOAuth2_putAccessToken(oauth2,'MICROSOFT_GRAPH_ACCESS_TOKEN');
CkRest_SetAuthOAuth2(rest,oauth2);

// Send the GET request to download the file.
uriPath := '/v1.0/me/drive/root:/Misc/wildlife/penguins.jpg:/content';
success := CkRest_SendReqNoBody(rest,'GET',uriPath);
if (CkRest_getLastMethodSuccess(rest) <> True) then
  begin
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    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 := CkRest_ReadResponseHeader(rest);
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 := CkBinData_Create();
    CkRest_ReadRespBd(rest,discard);
    CkRest_Disconnect(rest,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.
    CkRest_ClearAuth(rest);

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

    success := CkRest_Connect(rest,CkUrl__host(redirectUrl),CkUrl_getPort(redirectUrl),CkUrl_getSsl(redirectUrl),True);
    if (success <> True) then
      begin
        Memo1.Lines.Add(CkRest__lastErrorText(rest));
        Exit;
      end;

    // Send the request..
    success := CkRest_SendReqNoBody(rest,'GET',CkUrl__path(redirectUrl));
    CkUrl_Dispose(redirectUrl);
    if (CkRest_getLastMethodSuccess(rest) <> True) then
      begin
        Memo1.Lines.Add(CkRest__lastErrorText(rest));
        Exit;
      end;

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

  end;

if (statusCode >= 300) then
  begin

    // Read the error response body.
    sbJson := CkStringBuilder_Create();
    success := CkRest_ReadRespSb(rest,sbJson);
    if (success <> True) then
      begin
        Memo1.Lines.Add(CkRest__lastErrorText(rest));
        Exit;
      end;

    jsonErr := CkJsonObject_Create();
    CkJsonObject_putEmitCompact(jsonErr,False);
    CkJsonObject_LoadSb(jsonErr,sbJson);
    Memo1.Lines.Add(CkJsonObject__emit(jsonErr));

    Exit;
  end;

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

stream := CkStream_Create();
CkStream_putSinkFile(stream,localPath);

success := CkRest_ReadRespBodyStream(rest,stream,True);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    Exit;
  end;

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

CkRest_Dispose(rest);
CkOAuth2_Dispose(oauth2);
    CkBinData_Dispose(discard);
    CkStringBuilder_Dispose(sbJson);
    CkJsonObject_Dispose(jsonErr);
CkStream_Dispose(stream);

end;