REST server callbacks

As the asynchronous operations in some cases can take a long time and often don't end inside a single method invocation of a resource, the JAX-RS specifications provide utilities to register callbacks to invoke on suspended asynchronous response state changes. We can register two types of callbacks in RESTEasy:

• Completion callbacks executed at the end of the requests or when they fail
• Connection callbacks executed when a client connection is closed or lost

Here a sample of registration of a completion callback:

@GET
@Path("/withCallback")
public void asyncGetWithCallback(@Suspended final AsyncResponse asyncResponse) {
  asyncResponse.register(new CompletionCallback() {
      @Override
      public void onComplete(Throwable throwable) {
       if (throwable == null) {
            numberOfSuccessResponses++;
         } else {
            numberOfFailures...