Java HTTP client常见库

前言

每种编程语言里最常用的库恐怕是Http请求库了，如python里的requests包，nodejs里的request模块。
在Java世界里，也是百花齐放，山头林立。常用的有：

HttpURLConnection: 最早的JDK提供的类
Java 11提供的HttpClient
Apache HttpComponents项目中的HTTPClient
Square提供的OkHttpClient
Spring 自带的WebClient

Apache HttpComponents

该组件提供了两个核心类：

HttpCore: 更底层的传输处理类
HttpClient：基于HttpCore实现的HTTP-compliant 处理类

JDK 11+ HTTP Client使用举例

Post同步的json数据：

public void invokePost() {try {String requestBody = prepareRequest();HttpClient client = HttpClient.newHttpClient();HttpRequest request = HttpRequest.newBuilder().uri(URI.create("https://reqbin.com/echo/post/json")).POST(HttpRequest.BodyPublishers.ofString(requestBody)).header("Accept", "application/json").build();HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());System.out.println(response.body());} catch (IOException | InterruptedException e) {e.printStackTrace();}}private String prepareRequest() throws JsonProcessingException {var values = new HashMap<String, String>() {{put("Id", "12345");put("Customer", "Roger Moose");put("Quantity", "3");put("Price","167.35");}};var objectMapper = new ObjectMapper();String requestBody = objectMapper.writeValueAsString(values);return requestBody;}

发送异步请求：

public void invoke() throws URISyntaxException {HttpClient client = HttpClient.newBuilder().version(Version.HTTP_2).followRedirects(Redirect.NORMAL).build();HttpRequest request = HttpRequest.newBuilder().uri(new URI(URLConstants.URL)).GET().header(URLConstants.API_KEY_NAME, URLConstants.API_KEY_VALUE).timeout(Duration.ofSeconds(10)).build();client.sendAsync(request, BodyHandlers.ofString()).thenApply(HttpResponse::body).thenAccept(System.out::println).join();}

HTTP Client包装库

cVurl

cVurl is an open-source wrapper for the Java HTTP client. It is written in Java 11 and can be used with any JDK 11.0.2 or newer.

public void cVurl() {CVurl cVurl = new CVurl();//POSTResult result = cVurl.post("https://api.imgflip.com/caption_image").queryParams(Map.of("template_id", "112126428","username", "test-user","password", "123test321","text0", "text0","text1", "text1")).asObject(Result.class);System.out.println("CVurl POST: " + result);
}