HTTP Behind a Transport Seam

The HTTP client behind a seam

java.net.http.HttpClient (Java 11+) is the modern client:

HttpClient client = HttpClient.newBuilder()
    .connectTimeout(Duration.ofSeconds(5))
    .build();

HttpRequest req = HttpRequest.newBuilder()
    .uri(URI.create("https://api.example.com/users/1"))
    .header("Accept", "application/json")
    .timeout(Duration.ofSeconds(3))
    .GET()
    .build();

HttpResponse<String> res = client.send(req, HttpResponse.BodyHandlers.ofString());
if (res.statusCode() == 200) { /* body via res.body() */ }

But this course never puts a live client in a test — no network in the sandbox, and unit tests shouldn't need one anyway. The professional shape is the same as Module 8's Clock seam:

public interface HttpTransport {
    HttpResponse<String> send(HttpRequest req) throws Exception;
}

The service takes a transport; tests inject a canned-response transport. Everything about HTTP — status codes, headers, timeouts, retries — is then exercised deterministically. Real HttpClient usage belongs in integration tests on machines with a network.