org.asynchttpclient

Interface AsyncHandler<T>

Type Parameters:

T - Type of object returned by the Future.get()

All Known Subinterfaces:

ProgressAsyncHandler<T>, StreamedAsyncHandler<T>

All Known Implementing Classes:

AsyncCompletionHandler, AsyncCompletionHandlerBase, BodyDeferringAsyncHandler, ExtendedAsyncHandler, ResumableAsyncHandler, TransferCompletionHandler, WebDavCompletionHandlerBase, WebSocketUpgradeHandler

public interface AsyncHandler<T>

An asynchronous handler or callback which gets invoked as soon as some data is available when processing an asynchronous response.
Callback methods get invoked in the following order:

1. onStatusReceived(HttpResponseStatus),
2. onHeadersReceived(HttpResponseHeaders),
3. onBodyPartReceived(HttpResponseBodyPart), which could be invoked multiple times,
4. onCompleted(), once the response has been fully read.

Returning a AsyncHandler.State.ABORT from any of those callback methods will interrupt asynchronous response processing, after that only onCompleted() is going to be called.
AsyncHandler aren't thread safe, hence you should avoid re-using the same instance when doing concurrent requests. As an example, the following may produce unexpected results:

   AsyncHandler ah = new AsyncHandler() {....};
   AsyncHttpClient client = new AsyncHttpClient();
   client.prepareGet("http://...").execute(ah);
   client.prepareGet("http://...").execute(ah);
 

It is recommended to create a new instance instead. Do NOT perform any blocking operation in there, typically trying to send another request and call get() on its future. There's a chance you might end up in a dead lock. If you really to perform blocking operation, executed it in a different dedicated thread pool.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	AsyncHandler.State

Method Summary

Modifier and Type	Method and Description
AsyncHandler.State	onBodyPartReceived(HttpResponseBodyPart bodyPart) Invoked as soon as some response body part are received.
T	onCompleted() Invoked once the HTTP response processing is finished.
AsyncHandler.State	onHeadersReceived(HttpResponseHeaders headers) Invoked as soon as the HTTP headers has been received.
AsyncHandler.State	onStatusReceived(HttpResponseStatus responseStatus) Invoked as soon as the HTTP status line has been received
void	onThrowable(Throwable t) Invoked when an unexpected exception occurs during the processing of the response.

Method Detail

onThrowable

void onThrowable(Throwable t)

Invoked when an unexpected exception occurs during the processing of the response. The exception may have been produced by implementation of onXXXReceived method invocation.

Parameters:

t - a Throwable

onBodyPartReceived

AsyncHandler.State onBodyPartReceived(HttpResponseBodyPart bodyPart)
                               throws Exception

Invoked as soon as some response body part are received. Could be invoked many times. Beware that, depending on the provider (Netty) this can be notified with empty body parts.

Parameters:

bodyPart - response's body part.

Returns:

a AsyncHandler.State telling to CONTINUE or ABORT the current processing. Aborting will also close the connection.

Throws:

Exception - if something wrong happens

onStatusReceived

AsyncHandler.State onStatusReceived(HttpResponseStatus responseStatus)
                             throws Exception

Invoked as soon as the HTTP status line has been received

Parameters:

responseStatus - the status code and test of the response

Returns:

a AsyncHandler.State telling to CONTINUE or ABORT the current processing.

Throws:

Exception - if something wrong happens

onHeadersReceived

AsyncHandler.State onHeadersReceived(HttpResponseHeaders headers)
                              throws Exception

Invoked as soon as the HTTP headers has been received. Can potentially be invoked more than once if a broken server sent trailing headers.

Parameters:

headers - the HTTP headers.

Returns:

a AsyncHandler.State telling to CONTINUE or ABORT the current processing.

Throws:

Exception - if something wrong happens

onCompleted

T onCompleted()
       throws Exception

Invoked once the HTTP response processing is finished.
Gets always invoked as last callback method.

Returns:

T Value that will be returned by the associated Future

Throws:

Exception - if something wrong happens