Http/2 Client trong Java 9 là gì?

Http/2 Client API (Java 9 incubator module jdk.incubator.httpclient) cải tiến hiệu năng so với HTTP/1.1, hỗ trợ server push. Làm web nhanh hơn, hiệu quả hơn. Export package jdk.incubator.http chứa public API.

Kích hoạt trong JShell

C:\> jshell -v --add-modules jdk.incubator.httpclient
| Welcome to JShell -- Version 9.0.4

Ví dụ đầy đủ trong JShell

jshell> import jdk.incubator.http.*;
jshell> HttpClient httpClient = HttpClient.newHttpClient();
httpClient ==> jdk.incubator.http.HttpClientImpl@534df152

jshell> HttpRequest httpRequest = HttpRequest.newBuilder()
   ...>     .uri(new URI("https://www.google.com"))
   ...>     .GET()
   ...>     .build();
httpRequest ==> https://www.google.com GET

jshell> HttpResponse httpResponse = httpClient.send(httpRequest, HttpResponse.BodyHandler.asString());
httpResponse ==> jdk.incubator.http.HttpResponseImpl@609cd4d8

jshell> System.out.println(httpResponse.statusCode());
403

jshell> System.out.println(httpResponse.body());
<HTML response body>

3 lớp cốt lõi

Lớp	Mô tả
HttpClient	Tạo, cấu hình, gửi request (sync/async), quản lý connection pool, cookie, proxy, authenticator.
HttpRequest	Immutable builder: URI, method, headers, body (String, byte[], InputStream, Publisher), timeout, version (HTTP/1.1, HTTP/2).
HttpResponse<T>	Immutable: statusCode, headers, body (type T), version, URI. Body handler: asString(), asByteArray(), asInputStream(), discarding(), ofLines()...

Điểm mạnh

Hỗ trợ HTTP/2 (multiplexing, header compression HPACK, server push).
Async native: sendAsync() trả CompletableFuture<HttpResponse>.
Reactive Streams: body handler BodyHandler.asSubscriber() cho backpressure.
WebSocket support (Java 11+).
Không cần dependency external (Apache HttpClient, OkHttp).

Lưu ý

Java 9: incubator module (--add-modules jdk.incubator.httpclient). Java 11+: module chuẩn java.net.http, package java.net.http.