Async Http Client
Copyright 2010 Ning Inc

DESCRIPTION
-----------
Javadoc: http://sonatype.github.com/async-http-client/apidocs/index.html
Getting started: http://is.gd/kexrN (PDF)
                 http://is.gd/ja6My (HTML)

Async Http Client library purpose is to allow Java applications to easily execute HTTP requests and asynchronously process the HTTP responses. The library also supports the WebSocket Protocol. The Async HTTP Client library is simple to use. First, in order to add it to your Maven project, simply add this dependency:

         <dependency>
             <groupId>com.ning</groupId>
             <artifactId>async-http-client</artifactId>
             <version>1.7.0</version>
         </dependency>

You can also download the artifact

    http://search.maven.org

Then in your code you can simply do:

    import com.ning.http.client.*;
    import java.util.concurrent.Future;

    AsyncHttpClient asyncHttpClient = new AsyncHttpClient();
    Future<Response> f = asyncHttpClient.prepareGet("http://www.ning.com/ ").execute();
    Response r = f.get();

You can also accomplish asynchronous operation without using a Future if you want to receive and process the response in your handler:

    import com.ning.http.client.*;
    import java.util.concurrent.Future;

    AsyncHttpClient asyncHttpClient = new AsyncHttpClient();
    asyncHttpClient.prepareGet("http://www.ning.com/ ").execute(new AsyncCompletionHandler<Response>(){
        
        @Override
        public Response onCompleted(Response response) throws Exception{
            // Do something with the Response
            // ...
            return response;
        }
        
        @Override
        public void onThrowable(Throwable t){
            // Something wrong happened.
        }
    });

You can also mix Future with AsyncHandler to only retrieve part of the asynchronous response

    import com.ning.http.client.*;
    import java.util.concurrent.Future;

    AsyncHttpClient asyncHttpClient = new AsyncHttpClient();
    Future<Integer> f = asyncHttpClient.prepareGet("http://www.ning.com/ ").execute(new AsyncCompletionHandler<Integer>(){
        
        @Override
        public Integer onCompleted(Response response) throws Exception{
            // Do something with the Response
            return response.getStatusCode();
        }
        
        @Override
        public void onThrowable(Throwable t){
            // Something wrong happened.
        }
    });
    
    int statuѕCode = f.get();

 You have full control on the Response life cycle, so you can decide at any moment to stop processing what the server is sending back:

      import com.ning.http.client.*;
      import java.util.concurrent.Future;

      AsyncHttpClient c = new AsyncHttpClient();
      Future<String> f = c.prepareGet("http://www.ning.com/ ").execute(new AsyncHandler<String>() {
          private StringBuilder builder = new StringBuilder();

          @Override
          public STATE onStatusReceived(HttpResponseStatus status) throws Exception {
              int statusCode = status.getStatusCode();
               // The Status have been read
               // If you don't want to read the headers,body or stop processing the response
               return STATE.ABORT;
          }

          @Override
          public STATE onHeadersReceived(HttpResponseHeaders h) throws Exception {
              Headers headers = h.getHeaders();
               // The headers have been read
               // If you don't want to read the body, or stop processing the response
               return STATE.ABORT;
          }

          @Override
          public STATE onBodyPartReceived(HttpResponseBodyPart bodyPart) throws Exception {
               builder.append(new String(bodyPart.getBodyPartBytes()));
               return STATE.CONTINUE
          }

          @Override
          public String onCompleted() throws Exception {
               // Will be invoked once the response has been fully read or a ResponseComplete exception
               // has been thrown.
               return builder.toString();
          }

          @Override
          public void onThrowable(Throwable t) {
          }
      });
      
      String bodyResponse = f.get();

Finally, you can also configure the AsyncHttpClient via it's AsyncHttpClientConfig object:

        AsyncHttpClientConfig cf = new AsyncHttpClientConfig.Builder().setProxyServer(new ProxyServer("127.0.0.1", 38080)).build();
        AsyncHttpClient c = new AsyncHttpClient(cf);

Async Http Client also support WebSocket by simply doing:

         WebSocket websocket = c.prepareGet(getTargetUrl())
                .execute(new WebSocketUpgradeHandler.Builder().addWebSocketListener(new WebSocketTextListener() {

                    @Override
                    public void onMessage(String message) {
                    }

                    @Override
                    public void onOpen(WebSocket websocket) {
                        websocket.sendTextMessage("...").sendBinaryMessage("...");
                    }

                    @Override
                    public void onClose(.WebSocket websocket) {
                        latch.countDown();
                    }

                    @Override
                    public void onError(Throwable t) {
                    }
                }).build()).get();

The library uses Java non blocking I/O for supporting asynchronous operations. The default asynchronous provider is build on top of Netty (http://www.jboss.org/netty), but the library exposes a configurable provider SPI which allows to easily plug in other frameworks like Grizzly (http://grizzly.java.net)

       AsyncHttpClientConfig config = new AsyncHttpClientConfig.Builder().build();
       AsyncHttpClient client = new AsyncHttpClient(new GrizzlyAsyncHttpProvider(config), config);

Keep up to date on the library development by joining the Asynchronous HTTP Client discussion group

        http://groups.google.com/group/asynchttpclient