Java - Making multiple requests using HTTP2

Question

I have not been able to find any great examples to outline using Java 's new HTTP2 support.

In previous versions of Java ( Java 8 ) I was making many calls to a REST server using multiple threads.

I had a global list of parameters and I would go through the parameters to make different sorts of requests.

For example:

String[] params = {"param1","param2","param3" ..... "paramSomeBigNumber"};

for (int i = 0 ; i < params.length ; i++){

   String targetURL= "http://ohellothere.notarealdomain.commmmm?a=" + params[i];

   HttpURLConnection connection = null;

   URL url = new URL(targetURL);
   connection = (HttpURLConnection) url.openConnection();
   connection.setRequestMethod("GET");

   //Send request
   DataOutputStream wr = new DataOutputStream (
        connection.getOutputStream());
    wr.writeBytes(urlParameters);
    wr.close();

    //Get Response  
    InputStream is = connection.getInputStream();
    BufferedReader rd = new BufferedReader(new InputStreamReader(is));

//Do some stuff with this specific http response

}

In the previous code what I would do is construct multiple HTTP requests to the same server with just a little change in the parameter. This took a while to complete so I even would break up the work using threads so that each thread would work on some chunk of the param array.

With HTTP2 I would now not have to create a brand new connection every time. The problem is I do not quite understand how to implement this using the new versions of Java ( Java 9 - 11 ).

If I have an array param as I do previously how would I do the following:

1) Re-use the same connection?
2) Allow different threads to use the same connection?

Essentially I am looking for an example to do what I was doing previously but now utilizing HTTP2 .

Regards

Answer 1

This took a while to complete so I even would break up the work using threads so that each thread would work on some chunk of the param array.

With Java 11's HttpClient , this is actually very simple to achieve; all you need is the following snippet:

var client = HttpClient.newBuilder().version(HttpClient.Version.HTTP_2).build();

String[] params = {"param1", "param2", "param3", "paramSomeBigNumber"};

for (var param : params) {
    var targetURL = "http://ohellothere.notarealdomain.commmmm?a=" + param;
    var request = HttpRequest.newBuilder().GET().uri(new URI(targetURL)).build();
    client.sendAsync(request, HttpResponse.BodyHandlers.ofString())
          .whenComplete((response, exception) -> {
              // Handle response/exception here
          });
}

This uses HTTP/2 to send the request asynchronously and then handles the response String (or Throwable ) when it is received in a callback.