Now that the Java application has an authorization code, it can exchange it for an access_token required to make a request to a vehicle.

1. Obtain an access token

In the previous section, we retrieved an authorization code. The Java application must exchange the code for an access_token to make a request.

The access_token represents your application’s access to a vehicle on behalf of the vehicle owner.

After receiving the access_token, the user can be redirected to the /vehicle route which we will implement in the next step.

  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18
  • 19
  • 20
  • 21
  • 22
  • 23
  • 24
  • 25
  • 26
  • 27
  • 28
  • 29
  • 30
  • 31
  • 32
  • 33
  • 34
  • 35
  • 36
  • 37
  • 38
  • 39
  • 40
  • 41
  • 42
  • 43
  • 44
  • 45
  • 46
  • 47
  • 48
  • 49
  • 50
// src/main/java/Main.java

// global variable to save our accessToken
private static String access;

public static void main(String[] args) {

    get("/exchange", (req, res) -> {
        String code = req.queryMap("code").value();

        // TODO: Request Step 1: Obtain an access token
        Auth auth = client.exchangeCode(code);
        
        // in a production app you'll want to store this in some kind of persistent storage
        access = auth.getAccessToken();
        
        return "";
    })
}

2. Get vehicle attributes

Once the application has the access_token, it can send requests to a vehicle using Smartcar’s API.

Once we have the vehicle attributes, we'll serialize them as JSON to return to the client.

  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18
  • 19
  • 20
  • 21
  • 22
  • 23
  • 24
  • 25
  • 26
  • 27
  • 28
  • 29
  • 30
  • 31
  • 32
  • 33
  • 34
  • 35
  • 36
  • 37
  • 38
  • 39
  • 40
  • 41
  • 42
  • 43
  • 44
  • 45
  • 46
  • 47
  • 48
  • 49
  • 50
get("/vehicle", (req, res) -> {
    // TODO: Request Step 2: Get vehicle information
    VehicleIds vehiclesResponse = Smartcar.getVehicles(access);
    // the list of vehicle ids
    String[] vehicleIds = vehiclesResponse.getVehicleIds();
    
    // instantiate the first vehicle in the vehicle id list
    Vehicle vehicle = new Vehicle(vehicleIds[0], access);

    // Make a request to Smartcar API
    VehicleAttributes attributes = vehicle.attributes();
    System.out.println(gson.toJson(attributes));
    
    // {
    //     "id": "36ab27d0-fd9d-4455-823a-ce30af709ffc",
    //     "make": "TESLA",
    //     "model": "Model S",
    //     "year": 2014
    // }
    
    res.type("application/json");
    
    return gson.toJson(attributes);
}

Try it out

Make sure the server is running -

  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
  • $
./gradlew run

Now you can go to localhost:8000/login to see your Java app running!

Next steps