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{span:style=font-size:2em;font-weight:bold} Continuations {span}

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h1. Continuations API 

CXF offers Continuations API to manage asynchronous (suspended) invocations.

[ContinuationProvider|http://svn.apache.org/repos/asf/cxf/trunk/core/src/main/java/org/apache/cxf/continuations/ContinuationProvider.java] represents a transport capable of suspending and resuming the invocations on request. 

CXF offers Servlet3 and legacy Jetty Continuations HTTP as well as JMS ContinuationProvider implementations. 
ContinuationProvider can be used to get [Continuation|http://svn.apache.org/repos/asf/cxf/trunk/core/src/main/java/org/apache/cxf/continuations/Continuation.java] which representrepresents a current active or suspended invocation. 

The provider and continuations can be obtained from the current CXF message like this: 

{code:java}
import org.apache.cxf.continuations.ContinuationProvider;
import org.apache.cxf.continuations.Continuation;

ContinuationProvider provider = (ContinuationProvider)message.get(ContinuationProvider.class.getName())
Continuation continuation = (Continuation)provider.getContinuation();
{code} 

The continuation can be suspended and resumed. 

Calling Continuation.suspend() and returning from the current method/code is enough to get CXF suspending the request. Additionally throwing [SuspendedInvocationException|http://svn.apache.org/repos/asf/cxf/trunk/core/src/main/java/org/apache/cxf/continuations/SuspendedInvocationException.java] was required originally but is no longer required/recommended.

Resuming the continuation will get the suspended thread returning, this is typically done by a thread which has completed an asynchronous task. 

Advanced applications can register [ContinuationCallback|http://svn.apache.org/repos/asf/cxf/trunk/core/src/main/java/org/apache/cxf/continuations/ContinuationCallback.java] with the current exchange in order to get the notifications that a given Continuation has completed its work by returning the data to the client. 

The custom applications can interact directly with Continuations API. CXF also offers higher-level support for asynchronous invocations built on top of Continuations API.

 
h1. UseAsyncMethod

JAX-WS frontend supports this annotation, please check the [CXF Annotations|http://cxf.apache.org/docs/annotations.html] page for more information.

h1. JAX-RS 2.0 AsyncResponse

JAX-RS 2.0 AsyncResponse is implemented in terms of Continuations API. Please see [this section|http://cxf.apache.org/docs/jax-rs-basics.html#JAX-RSBasics-Suspendedinvocations] for more information. 

h1. Suspending invocations from CXF interceptors

Advanced custom CXF interceptors can suspend the incoming requests and resume them when needed. 
Example:

{code:java}
//TODO
{code}