public void testSend() {
        
        String url = "http://localhost:8080/TestRestServer/webresources/entities.customer/";        
        Client client = ClientBuilder.newClient();               
        JsonObject jsonObject = TestJsonObject.createJson(); //Ну тут я делаю в другом классе просто объект для примера
        WebTarget clientTarget = client.target(url);                
        Builder invocationBuilder  = clientTarget.request(MediaType.APPLICATION_JSON);
        invocationBuilder.header("some-header", "true");        
        Response response = invocationBuilder.post(Entity.entity(jsonObject.toString(), MediaType.APPLICATION_JSON));                
        System.out.println(response.getHeaderString("some-header"));
    }