B4X

Refresh HMRC OAuth2 Access Token

See more OAuth2 Examples

Demonstrates how to refresh an HMRC access token. B4X

Dim success As Boolean = False

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

'  See Get HMRC Access Token 
'  for sample code showing how to obtain a HMRC access token for desktop apps.

'  It is assumed we previously obtained an OAuth2 access token for HMRC.

Dim jsonToken As ChilkatJsonObject
jsonToken.Initialize
success = jsonToken.LoadFile("qa_data/tokens/hmrc.json")
If success <> True Then
    Log("Failed to load hmrc.json")
    Return
End If


'  The access token JSON looks something like this:

'  {
'    "token_type": "Bearer",
'    "scope": "user_impersonation",
'    "expires_in": "3599",
'    "ext_expires_in": "0",
'    "expires_on": "1524783438",
'    "not_before": "1524779538",
'    "resource": "https://mydomain.api.crm.dynamics.com",
'    "access_token": "...",
'    "refresh_token": "...",
'    "id_token": "..."
'  }

Dim oauth2 As ChilkatOAuth2
oauth2.Initialize("oauth2")

oauth2.TokenEndpoint = "https://test-api.service.hmrc.gov.uk/oauth/token"

'  Replace these with actual values.
oauth2.ClientId = "HMRC-CLIENT-ID"
oauth2.ClientSecret = "HMRC-CLIENT-SECRET"

'  Get the "refresh_token"
oauth2.RefreshToken = jsonToken.StringOf("refresh_token")

'  Send the HTTP POST to refresh the access token..
success = oauth2.RefreshAccessToken
If success <> True Then
    Log(oauth2.LastErrorText)
    Return
End If


'  Load the access token response into the json object 
jsonToken.Load(oauth2.AccessTokenResponse)

'  If an "expires_on" member does not exist, then add the JSON member by
'  getting the current system date/time and adding the "expires_in" seconds.
'  This way we'll know when the token expires.
If jsonToken.HasMember("expires_on") = False Then
    Dim dtExpire As ChilkatDateTime
    dtExpire.Initialize
    dtExpire.SetFromCurrentSystemTime
    dtExpire.AddSeconds(jsonToken.IntOf("expires_in"))
    jsonToken.AppendString("expires_on", dtExpire.GetAsUnixTimeStr(False))
End If


'  Save the new JSON access token response to a file.
'  The access + refresh tokens contained in this JSON will be needed for the next refresh.
Dim sbJson As ChilkatStringBuilder
sbJson.Initialize
jsonToken.EmitCompact = False
jsonToken.EmitSb(sbJson)
sbJson.WriteFile("qa_data/tokens/hmrc.json", "utf-8", False)

Log("OAuth2 authorization granted!")
Log("New Access Token = " & oauth2.AccessToken)