Java9新特性系列(HTTP 2 Client)

HTTP

HTTP,HyperText Transfer Protocol,即超文本传输协议。1999年6月定义了HTTP协议中现今广泛使用的一个版本——HTTP 1.1,HTTP/2标准于2015年5月正是发表。

HTTP/2与HTTP1.1的区别

  • HTTP/2采用二进制格式而非文本格式
  • 完全的多路复用
  • 使用头压缩,降低了开销
  • 让服务器可以主动推送(push)数据到客户端

Java9中新的Http Client

官方Feature

动机

The existing HttpURLConnection API and its implementation have numerous problems:

  • The base URLConnection API was designed with multiple protocols in mind, nearly all of which are now defunct (ftp, gopher, etc.).
  • The API predates HTTP/1.1 and is too abstract.
  • It is hard to use, with many undocumented behaviors.
  • It works in blocking mode only (i.e., one thread per request/response).
  • It is very hard to maintain.

摘要

Define a new HTTP client API that implements HTTP/2 and WebSocket, and can replace the legacy HttpURLConnection API. The API will be delivered as an incubator module, as defined in JEP 11, with JDK 9. This implies:

  • The API and implementation will not be part of Java SE.
  • The API will live under the jdk.incubtor namespace.
  • The module will not resolve by default at compile or run time.

总结

在Java9之前,都是使用HttpURLConnection,本身存在很多问题,比如只支持HTTP/1.1、很难用、只适用于blocking模式、很难维护等等。
在Java9中,提供了新的方式来处理HTTP调用,提供了新的HTTP Client,将替代HttpURLConnection,并提供对WebSocketHTTP/2的支持,且提供流和服务器推送等功能的API。

新的HTTP Client在jdk.incubtor.httpclient模块中,如果要使用,需要在模块声明文件(module-info.java)中引入:

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module main_module {
...
requires jdk.incubtor.httpclient;
...
}

使用举例

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HttpClient client = HttpClient.newHttpClient(); 
HttpRequest req = HttpRequest.newBuilder(URI.create("http://hellomypastor.net" )).GET().build();
HttpResponse<String> response = client.send(req, HttpResponse.BodyHandler.asString());
System.out.println(response.statusCode());
System.out.println(response.version().name());
System.out.println(response.body());
}
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