504使用Java HttpClient时的Gateaway超时

如何解决504使用Java HttpClient时的Gateaway超时

我有一个在POST调用的HTTP中侦听的服务。使用curl，Postman等软件，请求成功（状态码200）。

我需要从Java使用此服务。但是使用Java 11中的本机HttpClient，我得到了504网关超时...

HttpClient client = HttpClient.newHttpClient();
HttpRequest request = HttpRequest.newBuilder().
    header("Content-Type","application/json").
    uri(URI.create(service_url)).
    POST(HttpRequest.BodyPublishers.ofString(json_string)).build();
HttpResponse<String> res = client.send(request,HttpResponse.BodyHandlers.ofString());
System.out.println(res.statusCode()); // 504

尝试使用Apache HttpClient库，调用成功：

StringEntity requestEntity = new StringEntity(
    json_string,ContentType.APPLICATION_JSON);
CloseableHttpClient httpclient = HttpClients.createDefault();
HttpPost httpPost = new HttpPost(service_url);
httpPost.setEntity(requestEntity);
CloseableHttpResponse res = httpclient.execute(httpPost);
System.out.println(res.getStatusLine().getStatusCode()); //200

为什么它不适用于Java本机HttpClient？通话之间有什么区别？