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.