(C++) Refresh a Dynamics CRM OAuth2 Access Token

Demonstrates how to refresh an expiring Dynamics CRM access token using the refresh token. endpoint.

(If a REST API call fails with a 401 unauthorized error, an application can auto-recover by refreshing the access token, and then re-send the request using the new token.)

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#include <CkJsonObject.h>
#include <CkDateTime.h>
#include <CkHttpRequest.h>
#include <CkHttp.h>
#include <CkHttpResponse.h>
#include <CkFileAccess.h>

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

    //  We previously obtained an access token and saved the JSON to a file using this example:
    //  Get Dynamics CRM OAuth2 Access Token

    //  This example will examine the JSON and expiration date, and if near expiration will
    //  refresh the access token.

    CkJsonObject json;
    bool success = json.LoadFile("qa_data/tokens/dynamicsCrm.json");
    if (success != true) {
        return;
    }

    //  The contents of the JSON look 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": "..."
    //  }

    //  The "expires_on" value is a Unix time.
    CkDateTime dtExpire;
    dtExpire.SetFromUnixTime(false,json.IntOf("expires_on"));

    //  If this date/time expires within 10 minutes of the current system time, refresh the token.

    //  OK, we need to refresh the access token by sending a POST...
    // 

    CkHttpRequest req;
    req.AddParam("grant_type","refresh_token");
    req.AddParam("redirect_uri","http://localhost:3017/");
    req.AddParam("client_id","DYNAMICS-CRM-CLIENT-ID");
    req.AddParam("client_secret","DYNAMICS-CRM-SECRET-KEY");
    req.AddParam("refresh_token",json.stringOf("refresh_token"));
    req.AddParam("resource","https://mydynamicsdomain.api.crm.dynamics.com");

    CkHttp http;

    CkHttpResponse *resp = http.PostUrlEncoded("https://login.microsoftonline.com/DYNAMICS-ENDPOINT-GUID/oauth2/token",req);
    if (http.get_LastMethodSuccess() != true) {
        std::cout << http.lastErrorText() << "\r\n";
        return;
    }

    //  Load the JSON response.
    json.Load(resp->bodyStr());
    json.put_EmitCompact(false);

    //  Show the JSON response.
    std::cout << json.emit() << "\r\n";

    std::cout << "Response status code: " << resp->get_StatusCode() << "\r\n";

    //  If the response status code is not 200, then it's an error.
    if (resp->get_StatusCode() != 200) {
        return;
    }

    delete resp;

    //  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 (json.HasMember("expires_on") != true) {
        dtExpire.SetFromCurrentSystemTime();
        dtExpire.AddSeconds(json.IntOf("expires_in"));
        json.AppendString("expires_on",dtExpire.getAsUnixTimeStr(false));
    }

    //  Save the refreshed access token JSON to a file for future requests.
    CkFileAccess fac;
    fac.WriteEntireTextFile("qa_data/tokens/dynamicsCrm.json",json.emit(),"utf-8",false);
    }