Java 9 HttpClient with sendAsyncMulti / multiResponseAsync

Question

I am trying to experiment with Java 9's HttpClient.

The basic example as in HttpRequest's javadoc works without problems:

HttpResponse response = HttpRequest.create(new URI("http://stackoverflow.com/"))
       .version(java.net.http.HttpClient.Version.HTTP_2)
       .followRedirects(HttpClient.Redirect.ALWAYS)
       .GET()
       .response();

       int statusCode = response.statusCode();
       String responseBody = response.body(HttpResponse.asString());

       System.out.println("statusCode = " + statusCode);
       System.out.println("responseBody = " + responseBody);

However, when trying to use sendAsyncMulti, it does not work. No files are created in E:\foo, the println after join is not reached, there is also no exception, although I basically copied the example from HttpResponse.multiFile's Javadoc. I expected that some HTTP responses will be saved in that directory. I also tried to remove the HTTP2 and followRedirects, other URLs like google etc, but it did not change anything. What am I doing wrong?

CompletableFuture<Map<URI,Path>> cf =
    HttpRequest.create(new URI("http://stackoverflow.com/"))
        .version(java.net.http.HttpClient.Version.HTTP_2)
        .followRedirects(HttpClient.Redirect.ALWAYS)
        .GET()
        .multiResponseAsync(HttpResponse.multiFile(Paths.get("E:\\foo")));
Map<URI,Path> results = cf.join();
System.out.println("after join");

If it is relevant, this is the version I am using (latest version of JDK 9):

java version "9-ea"
Java(TM) SE Runtime Environment (build 9-ea+126)
Java HotSpot(TM) Server VM (build 9-ea+126, mixed mode)

Hi. I'm facing some strange thing. Module java.httpclient does not exist at all in latest JDK 9 (build 9-ea+159) — S. Kadakov, Mar 03 '17 at 08:33
@S.Kadakov: The HttpClient was in previous JDK 9 versions part of official API, but is now an incubator module, which means it is not resolved by default. This is done because an official API can hardly be changed, even if it proves to be bad API. see http://openjdk.java.net/jeps/110 — user140547, Mar 03 '17 at 09:13

Erunafailaro · Answer 1 · 2017-03-22T08:29:53.393

The method sendAsyncMulti makes use of an HTTP2-feature named server push.

Most http2 clients, i.e. modern browsers and also the implementation in jdk9, only use the new features if the host is contacted via https.

Most http2-servers will only send push promises, if the initial client request was an http2 request.

The following snippet works with java 9 build 9-ea-153:

URI uri = new URI("https://blog.cloudflare.com/announcing-support-for-http-2-server-push-2/");
HttpRequest request = ExampleUtils.createHttpRequest(uri);
HttpClient client = ExampleUtils.createHttpClient();

MultiMapResult<String> multiMapResult = client.sendAsync(request, MultiProcessor.asMap((req) -> {
            Optional<BodyHandler<String>> optional = Optional.of(HttpResponse.BodyHandler.asString());
            if (optional.isPresent()) {
                System.out.println(" - " + req.uri());
            }
            return optional;
        }, false))

        .orTimeout(2, TimeUnit.SECONDS)
        .join();

The full working example can be found at github: https://github.com/janweinschenker/jdk9-jigsaw-http2

The snippet is taken from https://github.com/janweinschenker/jdk9-jigsaw-http2/blob/master/src/main/java/de/holisticon/jdk9showcase/http2client/ResponseAsyncMultiExample.java

+1 for making the connection to push promises and the github links. However, a better test URL for the example would be https://http2-push.io/ That's a HTTP/2 push test site that (currently) gives me *3* entries in the `MultiMapResult`: the html, a .css and a .js resource. — Stefan Zobel, Mar 30 '18 at 00:55

Java 9 HttpClient with sendAsyncMulti / multiResponseAsync

1 Answers1