Building RESTful Web Services with Java EE 8

CompletableFuture

Finally, we can use CompletableFuture as an alternative syntactic sugar way of using those asynchronous REST APIs. Again, we use a ManagedExecutorService instance here. The next thing we want to do is use CompletableFuture to run the Fibonacci calculation asynchronously and then apply the asyncResponse::resume method. The code will look as follows. Using CompletableFuture, we call the runAsync method, run our Fibonacci calculation using the supplied executorService, and then apply the asyncResponse::resume method:

    @GET    @Path("/{i}")    public void completable(@Suspended final AsyncResponse       asyncResponse, @PathParam("i") final int i) {        CompletableFuture                .runAsync(() -> fibonacci(i), executorService) .thenApply(asyncResponse::resume); ...