Asynchronous JAX-RS - RESTful Java with JAX-RS 2.0 - page 193

exceptions from the JAX-RS error exception hierarchy (i.e., NotFoundException or
BadRequestException ). If an exception is thrown while you're unmarshalling the response
to a Order , then ResponseProcessingException is thrown.

WARNING

You should always make sure that the underlying JAX-RS response is closed. While most JAX-RS
containers will have their Response objects implement a finalize() method, it is not a good idea
to rely on the garbage collector to clean up your client connections. If you do not clean up your con-
nections, you may end up with intermittent errors that pop up if the underlying Client or operating
system has exhausted its limit of allowable open connections.

In fact, if we examine our initial example a bit further, there's a lot of code we have to add to
ensure that we are being good citizens and closing any open Response objects. Here's what
the final piece of code would look like:

Client client = ClientBuilder . newClient ();

Future < Response > future1 = client . target ( "http://example.com/service" )
. request ()
. async (). get ();

Future < Order > future2 = null null ;

try try {

future2 = client . target ( "http://foobar.com/service2" )
. request ()
. async (). get ( Order . class );

} catch catch ( Throwable ignored ) {

ignored . printStackTrace ();

}

// block until complete
Response res1 = future1 . get ();
try try {

Customer result1 = res . readEntity ( Customer . class );
} catch catch ( Throwable ignored ) {

ignored . printStackTrace ();
} finally

finally {
res1 . close ();

}

// if we successfully executed 2nd request
iif ( future2 != null

null ) {
// Wait 5 seconds