(DataFlex) Refresh GMail SMTP OAuth2 Access Token

Demonstrates how to refresh an access token for sending email via GMail (SMTP).

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

Use ChilkatAx-win32.pkg

Procedure Test
    Handle hoJsonToken
    Boolean iSuccess
    Handle hoOauth2
    Variant vSbJson
    Handle hoSbJson
    String sTemp1

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

    // See Get GMail SMTP Access Token 
    // for sample code showing how to obtain a GMail SMTP access token for desktop apps.

    // It is assumed we previously obtained an OAuth2 access token for GMail (one with a scope for sending email).

    Get Create (RefClass(cComChilkatJsonObject)) To hoJsonToken
    If (Not(IsComObjectCreated(hoJsonToken))) Begin
        Send CreateComObject of hoJsonToken
    End
    Get ComLoadFile Of hoJsonToken "qa_data/tokens/_gmailSmtp.json" To iSuccess
    If (iSuccess <> True) Begin
        Showln "Failed to load _gmailSmtp.json"
        Procedure_Return
    End

    // The access token JSON looks something like this:

    // 	{ 
    // 	 "access_token": "abac.Ci-ZabcdF37-NUrmSzxbHxTsMbtlN-uPfabcdAQN_2ekzj0s5ofCzRabcdTDMGaa2Q",
    // 	 "token_type": "Bearer",
    // 	 "expires_in": 3600,
    // 	 "refresh_token": "1/lEe5abcdNJ77eOSDBabcdkQGVmDalkwabcdR2Hatbo"
    // 	}
    // 

    Get Create (RefClass(cComChilkatOAuth2)) To hoOauth2
    If (Not(IsComObjectCreated(hoOauth2))) Begin
        Send CreateComObject of hoOauth2
    End

    Set ComTokenEndpoint Of hoOauth2 To "https://www.googleapis.com/oauth2/v4/token"

    // Replace these with actual values.
    Set ComClientId Of hoOauth2 To "GOOGLE-CLIENT-ID"
    Set ComClientSecret Of hoOauth2 To "GOOGLE-CLIENT-SECRET"

    // Get the "refresh_token"
    Get ComStringOf Of hoJsonToken "refresh_token" To sTemp1
    Set ComRefreshToken Of hoOauth2 To sTemp1

    // Send the HTTP POST to refresh the access token..
    Get ComRefreshAccessToken Of hoOauth2 To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoOauth2 To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // The response contains a new access token, but we must keep
    // our existing refresh token for when we need to refresh again in the future.
    Get ComAccessToken Of hoOauth2 To sTemp1
    Get ComUpdateString Of hoJsonToken "access_token" sTemp1 To iSuccess

    // Save the new JSON access token response to a file.
    Get Create (RefClass(cComChilkatStringBuilder)) To hoSbJson
    If (Not(IsComObjectCreated(hoSbJson))) Begin
        Send CreateComObject of hoSbJson
    End
    Set ComEmitCompact Of hoJsonToken To False
    Get pvComObject of hoSbJson to vSbJson
    Get ComEmitSb Of hoJsonToken vSbJson To iSuccess
    Get ComWriteFile Of hoSbJson "qa_data/tokens/_gmailSmtp.json" "utf-8" False To iSuccess

    Showln "OAuth2 authorization granted!"
    Get ComAccessToken Of hoOauth2 To sTemp1
    Showln "New Access Token = " sTemp1


End_Procedure