Java Reference
In-Depth Information
" + wae . getResponse (). getStatus ());
} else
else iif ( throwable instanceof
instanceof ResponseProcessingException ) {
ResponseProcessingException rpe = ( ResponseProcessingException ) cause ;
System . err . println ( "Failed with status:
" + rpe . getResponse (). getStatus ());
} else
else {
throwable . printStackTrace ();
This case is a little bit different than when we implement InvocationCallback with a Re-
sponse . If there is a successful HTTP response from the server (like 200, “OK”), JAX-RS
will attempt to unmarshal the response into an Order object. If there were an HTTP error re-
sponse, or the JAX-RS runtime failed to unmarshal the response body into an Order object,
then the failed() method is invoked with the appropriate exception. Basically, we see the
same kind of exceptions thrown by similar synchronous invocations or the Future example
we discussed earlier. You do not have to close the underlying Response object; JAX-RS will
do this after completed() or failed() is invoked.
Now that our callback classes have been implemented, let's finish our example by invoking
on some services:
Client client = ClientBuilder . newClient ();
Future < Response > future1 = client . target ( "" )
. request ()
. async (). get ( new
new CustomerCallback ());
Future < Order > future2 = client . target ( "" )
. request ()
. async (). get ( new
new OrderCallback ());
That's all we have to do. Notice that the get() methods return a Future object. You can ig-
nore this Future , or interact with it as we did previously. I suggest that you only use the Fu-
ture.cancel() and Future.isDone() methods, though, as you may have concurrency is-
sues with InvocationCallback .
Futures Versus Callbacks
Given that we have two different ways to do asynchronous client invocations, which style
should you use? Futures or callbacks? In general, use futures if you need to join a set of re-
quests you've invoked asynchronously. By join , I mean you need to know when each of the
Search WWH ::

Custom Search