Asynchronous JAX-RS - RESTful Java with JAX-RS 2.0 - page 194

try try {

Order result2 = future2 . get ( 5 , TimeUnit . SECONDS );
} catch catch ( TimeoutException timeout ) {

System . err . println ( "request timed out" );
} catch catch ( InterruptedException ie ) {

System . err . println ( "Request was interrupted" );
} catch

catch ( ExecutionException ee ) {
Throwable cause = ee . getCause ();

iif ( cause instanceof instanceof WebApplicationException ) {

( WebApplicationException ) wae = ( WebApplicationException ) cause ;
wae . close ();
} else instanceof ResponseProcessingException ) {

ResponseProcessingException rpe = ( ResponseProcessingException ) cause ;
rpe . close ();
} else

else iif ( cause instanceof

instanceof ProcessingException ) {
// handle processing exception
} else

else iif ( cause instanceof

else {
// unknown

}

}

}

As you can see, there's a few more try/catch blocks we need to add to make sure that the
response of each async request is closed.

Using Callbacks

The AsyncInvoker interface has an additional callback invocation style. You can register an
object that will be called back when the asynchronous invocation is ready for processing:

package package javax . ws . rs . client ;

public public interface AsyncInvoker {

< T > Future < T > get ( InvocationCallback < T > callback );
< T > Future < T > post ( Entity <?> entity , InvocationCallback < T > callback );
< T > Future < T > put ( Entity <?> entity , InvocationCallback < T > callback );
< T > Future < T > delete ( Entity <?> entity , InvocationCallback < T > callback );

interface AsyncInvoker

...

}

The InvocationCallback interface is a parameterized generic interface and has two simple
methods you have to implement—one for successful responses, the other for failures: