@Stateless
@Path("entities.customer")
public class CustomerFacadeREST extends AbstractFacade<Customer> {
    @PersistenceContext(unitName = "TestRestServerPU")
    private EntityManager em;

    public CustomerFacadeREST() {
        super(Customer.class);
    }

    @POST
    @Consumes({"application/json"})
    public void create(JsonObject jsonObj) {
        System.out.println("I got JSON:   " + jsonObj.toString());
    }

public class TestRestClient {

    public static void main(String[] args) {        
        TestRestClient testRest = new TestRestClient();
        testRest.testSend();
    }
    
    public void testSend() {
        JsonObject jsonObject = Json.createObjectBuilder()
                .add("userName", "user")
                .add("password", "secret")
                .build();
        System.out.println(jsonObject.toString());        

        String url = "http://localhost:8080/TestRestServer/webresources/entities.customer/";
        
        Client client = ClientBuilder.newClient();          
        client.register(jsonObject);
        WebTarget clientTarget = client.target(url);
        
        Builder invocationBuilder  = clientTarget.request(MediaType.APPLICATION_JSON);
        
        Response response = invocationBuilder.post(Entity.entity(jsonObject.toString(), MediaType.APPLICATION_JSON));
    }
}