TOAuth2Authenticator: How do i refresh an expired token? - rest

Question

I must be missing something here!
I have been playing around trying to refresh an expired OAUTH2 token using the new ( new to me anyway, coming from delphi xe2 environment) TOAuth2Authenticator, TRESTClient, TRESTRequest, TRESTResponse components
I have set the following authenticator properties with the existing known values for
ClientID
ClientSecret
Scope
AccessTokenEndPoint
AuthorizationEndPoint
RedirectionEndPoint
AccessToken
AccessTokenExpiry
RefreshToken
and can successful access resources from the REST server, up until the token expires.
I presumed (wrongly, so it seems) if I try an execute a request against a server, and the token had expired, there should be enough detail for the component to realise the token has expired and refresh it as and when it need to.
I take it there is no hidden/undocumented "RefreshExpiredToken" method that I can call?
Any pointers in the right direction would be greatly appreciated :-)
Thanks

Answer 1

I eventually figured this out, by bastardising the publicTOAuth2Authticator.ChangeAuthCodeToAccessToken procedure, but thought I'd post my solution just in case it helps anyone else out:
LClient := TRestClient.Create(AccessTokenURI);
try
LRequest := TRESTRequest.Create(LClient); // The LClient now "owns" the Request and will free it.
LRequest.Method := TRESTRequestMethod.rmPOST;
LSecretBase64 := String(SZFullEncodeBase64(AnsiString(<myClientID>+ ':' + <MyClientSecret>)));
LRequest.AddAuthParameter('grant_type', 'refresh_token', TRESTRequestParameterKind.pkGETorPOST);
LRequest.AddAuthParameter('refresh_token', _AccessRefreshToken, TRESTRequestParameterKind.pkGETorPOST);
LRequest.AddAuthParameter('Authorization','Basic '+LSecretBase64, TRESTRequestParameterKind.pkHTTPHEADER, [TRESTRequestParameterOption.poDoNotEncode] );
LRequest.Execute;
//Memo1.Lines.Add(LRequest.Response.Content);
if LRequest.Response.GetSimpleValue('access_token', LToken) then
begin
_AccessToken := LToken;
end;
if LRequest.Response.GetSimpleValue('refresh_token', LToken) then
begin
_AccessRefreshToken := LToken;
//Memo1.Lines.Add('RefreshExpiredToken: New Refresh Token Extracted');
end;
// detect token-type. this is important for how using it later
if LRequest.Response.GetSimpleValue('token_type', LToken)
then _TokenType := OAuth2TokenTypeFromString(LToken);
// if provided by the service, the field "expires_in" contains
// the number of seconds an access-token will be valid
if LRequest.Response.GetSimpleValue('expires_in', LToken) then
begin
LIntValue := StrToIntdef(LToken, -1);
if (LIntValue > -1) then
_AccessTokenExpireDT := IncSecond(Now, LIntValue)
else
_AccessTokenExpireDT := 0.0;
//Memo1.Lines.Add('RefreshExpiredToken: New Token Expires '+formatdatetime('hh:nn:ss dd/mm/yyyy', _AccessTokenExpireDT));
end;
finally
LClient.DisposeOf;
end;