HttpAsyncClient Quick Start

  • Download ‘Binary’ package of the latest HttpAsyncClient 4.1 release or configure dependency on HttpAsyncClient module using a dependency manager of your choice as described here.

  • HttpAsyncClient 4.1 requires Java 1.6 or newer.

  • The code fragment below illustrates the most fundamental aspects of asynchronous request execution with HttpAsyncClient.

CloseableHttpAsyncClient httpclient = HttpAsyncClients.createDefault();
try {
    // Start the client
    httpclient.start();

    // Execute request
    final HttpGet request1 = new HttpGet("http://www.apache.org/");
    Future<HttpResponse> future = httpclient.execute(request1, null);
    // and wait until a response is received
    HttpResponse response1 = future.get();
    System.out.println(request1.getRequestLine() + "->" + response1.getStatusLine());

    // One most likely would want to use a callback for operation result
    final CountDownLatch latch1 = new CountDownLatch(1);
    final HttpGet request2 = new HttpGet("http://www.apache.org/");
    httpclient.execute(request2, new FutureCallback<HttpResponse>() {

        public void completed(final HttpResponse response2) {
            latch1.countDown();
            System.out.println(request2.getRequestLine() + "->" + response2.getStatusLine());
        }

        public void failed(final Exception ex) {
            latch1.countDown();
            System.out.println(request2.getRequestLine() + "->" + ex);
        }

        public void cancelled() {
            latch1.countDown();
            System.out.println(request2.getRequestLine() + " cancelled");
        }

    });
    latch1.await();

    // In real world one most likely would also want to stream
    // request and response body content
    final CountDownLatch latch2 = new CountDownLatch(1);
    final HttpGet request3 = new HttpGet("http://www.apache.org/");
    HttpAsyncRequestProducer producer3 = HttpAsyncMethods.create(request3);
    AsyncCharConsumer<HttpResponse> consumer3 = new AsyncCharConsumer<HttpResponse>() {

        HttpResponse response;

        @Override
        protected void onResponseReceived(final HttpResponse response) {
            this.response = response;
        }

        @Override
        protected void onCharReceived(final CharBuffer buf, final IOControl ioctrl) throws IOException {
            // Do something useful
        }

        @Override
        protected void releaseResources() {
        }

        @Override
        protected HttpResponse buildResult(final HttpContext context) {
            return this.response;
        }

    };
    httpclient.execute(producer3, consumer3, new FutureCallback<HttpResponse>() {

        public void completed(final HttpResponse response3) {
            latch2.countDown();
            System.out.println(request3.getRequestLine() + "->" + response3.getStatusLine());
        }

        public void failed(final Exception ex) {
            latch2.countDown();
            System.out.println(request3.getRequestLine() + "->" + ex);
        }

        public void cancelled() {
            latch2.countDown();
            System.out.println(request3.getRequestLine() + " cancelled");
        }

    });
    latch2.await();

} finally {
    httpclient.close();
}
  • Take a look at the HttpCore tutorial for introduction to fundamentals of asynchronous HTTP communication with HttpComponents 4.x.

  • Another good way of getting started with HttpAsyncClient is by seeing it in action. Take a look at the samples shipped with the release package or available online.