getAccessToken() returns null

[RobinJayaswal]

try {
      ... get code ...

      System.out.println(code);
      Access access = client.exchangeCode(code);
      System.out.println(access.getAccessToken());
      Api.Vehicles vehicles = client.getVehicles(access.getAccessToken());

} catch (Exception e) {
     System.out.println(e);
}

This prints out

f7583f02-3a1c-4539-9a69-285799abf6f7
null
com.smartcar.sdk.Exceptions$AuthenticationException: {"error":"authentication_error","message":"Invalid or expired token provided."}

[RobinJayaswal]

Fixed, . The problem was with gson.fromJson(json, Access.class).

The json string has property names that are lower case with underscores, and gson looks for exact matches to the constructor parameters, which are camel case. You just have to configure gson to expect this capitalization:

private final Gson gson = new GsonBuilder().setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES).create();

Pr #10 fixes.