How do you consume http response content asynchronously with Apache's HTTP async client?

Question

I'm new to Java NIO. I'm using it to make HTTP Get requests. The requests executes properly, but I am unable to figure out how to get the content of the response.

For example,

CloseableHttpAsyncClient httpClient = HttpAsyncClients.createDefault();
httpClient.start();
url = buildUrl(); //builds the url for the GET request
BasicAsyncResponseConsumer consumer = new BasicAsyncResponseConsumer();
 Future<HttpResponse> future = httpClient.execute(HttpAsyncMethods.createGet(url), consumer, null)

Now how do I get the content of the response? On printing future, I get the following:

HTTP/1.1 200 OK [Content-Type: application/json, Date: Fri, 24 Jun 2016 20:21:47 GMT, Content-Length: 903, Connection: keep-alive] [Content-Length: 903,Chunked: false]

My response (on the browser) is 903 characters, so I know the it makes the request correctly. However, how do I print out the json content of the result?

Which library are you using? you don't appear to be using NIO. — Peter Lawrey, Jun 24 '16 at 20:38
You might have used NIO before, but not in the code you mention here. hint: are you using any classes in the `java.nio` package? — Peter Lawrey, Jun 25 '16 at 10:21

score 1 · Answer 1 · answered Jun 25 '16 at 01:31

There are a couple of ways for you to approach this.

One, call get() on the Future returned by execute, blocking until a result is ready. Once the result is ready, get() will return the HttpResponse object which you can use to retrieve the content with getEntity. The HttpEntity has an InputStream. Read it however you think is appropriate.

Two, provide a smarter HttpAsyncResponseConsumer implementation than BasicAsyncResponseConsumer which reads (and closes) the HttpResponse's HttpEntity and produces a value that can be consumed by the FutureCallback value that is expected as the third argument to HttpAsyncClient#execute. This solution will not block your current thread.

get() will be called only when all the response content has been stored in a local buffer if we use BasicAsyncResponseConsumer . But thats not what the ask is. We want to stream the response body directly and not store it in local buffer. — lostintranslation, May 07 '18 at 13:25

How do you consume http response content asynchronously with Apache's HTTP async client?

1 Answers1