DropWizard/Jersey API Clients

Question

DropWizard uses Jersey under the hood for REST. I am trying to figure out how to write a client for the RESTful endpoints my DropWizard app will expose.

For the sake of this example, let's say my DropWizard app has a CarResource, which exposes a few simple RESTful endpoints for CRUDding cars:

@Path("/cars")
public class CarResource extends Resource {
    // CRUDs car instances to some database (DAO).
    public CardDao carDao = new CarDao();

    @POST
    public Car createCar(String make, String model, String rgbColor) {
        Car car = new Car(make, model, rgbColor);
        carDao.saveCar(car);

        return car;
    }

    @GET
    @Path("/make/{make}")
    public List<Car> getCarsByMake(String make) {
        List<Car> cars = carDao.getCarsByMake(make);
        return cars;
    }
}

So I would imagine that a structured API client would be something like a CarServiceClient:

// Packaged up in a JAR library. Can be used by any Java executable to hit the Car Service
// endpoints.
public class CarServiceClient {
    public HttpClient httpClient;

    public Car createCar(String make, String model, String rgbColor) {
        // Use 'httpClient' to make an HTTP POST to the /cars endpoint.
        // Needs to deserialize JSON returned from server into a `Car` instance.
        // But also needs to handle if the server threw a `WebApplicationException` or
        // returned a NULL.
    }

    public List<Car> getCarsByMake(String make) {
        // Use 'httpClient' to make an HTTP GET to the /cars/make/{make} endpoint.
        // Needs to deserialize JSON returned from server into a list of `Car` instances.
        // But also needs to handle if the server threw a `WebApplicationException` or
        // returned a NULL.
    }
}

But the only two official references to Drop Wizard clients I can find are totally contradictory to one another:

• DropWizard recommended project structure - which claims I should put my client code in a car-client project under car.service.client package; but then...
• DropWizard Client manual - which makes it seem like a "DropWizard Client" is meant for integrating my DropWizard app with other RESTful web services (thus acting as a middleman).

So I ask, what is the standard way of writing Java API clients for your DropWizard web services? Does DropWizard have a client-library I can utilize for this type of use case? Am I supposed to be implementing the client via some Jersey client API? Can someone add pseudo-code to my CarServiceClient so I can understand how this would work?

Answer 1

Here is a pattern you can use using the JAX-RS client.

To get the client:

javax.ws.rs.client.Client init(JerseyClientConfiguration config, Environment environment) {
    return new JerseyClientBuilder(environment).using(config).build("my-client");
}

You can then make calls the following way:

javax.ws.rs.core.Response post = client
        .target("http://...")
        .request(MediaType.APPLICATION_JSON)
        .header("key", value)
        .accept(MediaType.APPLICATION_JSON)
        .post(Entity.json(myObj));