Apache Async Http Client

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This example demonstrates a basic asynchronous HTTP request / response exchange. Response content is buffered in memory for simplicity.

This example demonstrates an asynchronous HTTP request / response exchange with a full content streaming.

Apache HttpComponents AsyncClient License: Apache 2.0: Categories: HTTP Clients: Tags: apache client http: Used By: 629 artifacts: Central (16) AtlassianPkgs (2. Apache Async HTTP Client uses NIO. Jersey is a ReST client/server framework; the client API can use several HTTP client backends including URLConnection and Apache HTTP Client.

This example demonstrates an asynchronous HTTP request / response exchange with a full content streaming. Concurrent asynchronous HTTP exchanges This example demonstrates a fully asynchronous execution of multiple HTTP exchanges where the result of an individual operation is reported using a callback interface. Update to Apache Async HTTP client 4.1 when released. Update to version 4.1 of the Apache client. The test should pass again.

This example demonstrates how to avoid the illegal reflective access operation warning when running with Oracle JRE 9 or newer.

This example demonstrates a pipelined execution of multiple HTTP/1.1 request / response exchanges. Response content is buffered in memory for simplicity.

Apache Async Http Client Retry

This example demonstrates a multiplexed execution of multiple HTTP/2 request / response exchanges. Response content is buffered in memory for simplicity.

This example demonstrates how to insert custom request interceptor and an execution interceptor to the request execution chain.

This example demonstrates how to use a custom execution interceptor to add trailers to all outgoing request enclosing an entity..

This example demonstrates handling of HTTP/2 message exchanges pushed by the server.

This example demonstrates execution of an HTTP request against a target site that requires user authentication.

This example demonstrates how to create secure connections with a custom SSL context.

This example demonstrates how to evict expired and idle connections from the connection pool.

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By default, CXF uses a transport based on the in-JDK HttpURLConnection object to perform HTTP requests. The HttpURLConnection object uses a blocking model for all IO operations which requires a per-thread execution model. From a pure performance standpoint, this model generally performs very well, but it does have problems scaling when many requests need to be executed simultaneously.

Also, the JAX-WS specification allows for generation of asynchronous methods on generated proxies as well as using asynchronous methods on the Dispatch objects. These methods can take an AsyncHandler object and return a polling Future object so applications do not have to wait for the response. With the HttpURLConnection based transport, CXF was forced to consume a background thread for each outstanding request.


CXF also has an HTTP client transport that is based on the Apache HTTP Components HttpAsyncClient library. Its Maven artifactId is cxf-rt-transports-http-hc. The HttpAsyncClient library uses a non-blocking IO model. This allows many more requests to be outstanding without consuming extra background threads. It also allows greater control over things like Keep-Alive handling which is very difficult or impossible with the HttpURLConnection based transport. However, the non-blocking model does not perform quite as well as the blocking model for pure synchronous request/response transactions.

By default, if the cxf-rt-transports-http-hc module is found on the classpath, CXF will use the HttpAsyncClient based implementation for any Async calls, but will continue to use the HttpURLConnection based transport for synchronous calls. This allows a good balance of performance for the common synchronous cases with scalability for the asynchronous cases. However, using a contextual property of 'use.async.http.conduit' and set to true/false, you can control whether the async or blocking version is used. If 'true', the HttpAsyncClient will be used even for synchronous calls, if 'false', asynchronous calls will rely on the traditional method of using HTTPURLConnection along with a work queue to mimic the asynchronocity. And if TLSClientParameters sets an SSLSocketFactory, as SocketFactory class and SocketFactory#createSocket methods in particular are inherently blocking and sockets instantiated in such a way cannot be used for asynchronous, so this lead to use the HttpURLConnection based transport.

Another reason to use the asynchronous transport is to use HTTP methods that HttpURLConnection does not support. For example, the github.com REST API specifies the use of PATCH for some cases, but HttpURLConnection rejects PATCH.

Using the HTTP Components Transport from Java Code

Apache Async Http Client

To force global use of the HTTP Components transport, you can set a bus-level property:

The 'normal' CXF/JAX-WS method of setting user credentials via the BindingProvider.USERNAME_PROPERTY/PASSWORD_PROPERTY will work with the Async transport as well. However, the HttpAsyncClient library does have some additional capabilities around NTLM that can be leveraged. In order to use that, you need to:

  • Turn on the AutoRedirect and turn off the Chunking for the Conduit. This will allow CXF to cache the response in a manner that will allow the transport to keep resending the request during the authentication negotiation.
  • Force the use of the Async transport even for synchronous calls

  • Set the property 'org.apache.http.auth.Credentials' to an instance of the Credentials. For example:

Apache Async Http Client


The Asynchronous HTTP Transport has several options that can set using Bus properties or via the OSGi configuration services to control various aspects of the underlying Apache HTTP Components HttpAsyncClient objects.

Settings related to the underlying TCP socket (see java.net.Socket for a definition of these values):

org.apache.cxf.transport.http.async.TCP_NODELAY (Default true)




Settings related to Keep-Alive connection management:

Apache Async Http Client Keep Alive


Maximum time a connection to live(from creation to expiry). Default is 60000.


Maximum number of connections opened in total. Default is 5000.


Maximum number of connections opened per host. Default is 1000.

Settings related to Apache HttpAsyncClient threads and selectors:


Number of threads HttpAsyncClient uses to process IO events. Default is '-1' which means one thread per CPU core.


true/false for whether the interest ops are queues or process directly.


Default 1000 ms. How often the selector thread wakes up if there are no events to process additional things like queue expirations.

Apache Async Http Client Connection Pool

Setting to control which conduit is used



Similar in meaning to the 'use.async.http.conduit' context property described above. Whether to use the HttpAsyncClient: ALWAYS for both synchronous and asynchronous calls, ASYNC_ONLY (default) for asynchronous calls only, NEVER will use HTTPURLConnection for both types of calls.