Asynchronous JAX-RS - RESTful Java with JAX-RS 2.0 - page 195

package package javax . rs . ws . client ;

public public interface interface InvocationCallback InvocationCallback < RESPONSE > {

public public void void completed ( RESPONSE response );

public public void void failed ( Throwable throwable );

}

JAX-RS introspects the application class that implements InvocationCallback to determ-
ine whether your callback wants a Response object or if you want to unmarshal to a specific
type. Let's convert our Future example to use callbacks. First, we'll implement a callback
for our initial request:

public public class class CustomerCallback CustomerCallback implements implements InvocationCallback < Response > {

public public void void completed ( Response response ) {

iif ( response . getStatus () == 200 ) {
Customer cust = response . readEntity ( Customer . class );
} else else {

System . err . println ( "Request error: " + response . getStatus ());

}

}

public public void void failed ( Throwable throwable ) {

throwable . printStackTrace ();

}

}

The CustomerCallback class implements InvocationCallback with a Response generic
parameter. This means JAX-RS will call the completed() method and pass in an untouched
Response object. If there is a problem sending the request to the server or the JAX-RS
runtime is unable to create a Response , the failed() method will be invoked with the ap-
propriate exception. Otherwise, if there is an HTTP response, then completed() will be
called.

Next, let's implement a different callback for our second parallel request. This time we want
our successful HTTP responses to be converted into Order objects:

public public class class OrderCallback OrderCallback implements implements InvocationCallback < Order > {

public public void void completed ( Order order ) {

System . out . println ( "We received an order." );

}

public public void void failed ( Throwable throwable ) {

iif ( throwable instanceof instanceof WebApplicationException ) {

WebApplicationException wae = ( WebApplicationException ) throwable ;
System . err . println ( "Failed with status: