Reactive programming met Java 8 en Java EE 7, transform a synchronous, blocking REST-service to a non-blocking, asychronous, reactive service with completable futures

1. Reactive programming
met Java SE 8 en Java EE 7
Martijn Blankestijn

2. Agenda
● Context
● Sequence, zonder futures
● Futures
● CompletableFuture
● Round-up

3. Context
Our
responsiblity

4. @Path("customers") public class DemoOverviewResource {
@GET @Path("{username}")
@Produces(APPLICATION_JSON)
public CustomerOverview retrieve(
@PathParam("username") String username) {
Customer customer = getCustomerInfo(username);
Contract[] contracts = getContracts(customer);
Communication[] communications = getCommunications(customer);
return createOverview(
customer,
contracts,
communications);
}

5. Customer
Contract
Communications
TIME
Sequential

6. A Future
represents
the result
of an
asynchronous computation

7. public interface Future<V> {
boolean isDone();
V get()
V get(long timeout, TimeUnit unit)

9. Customer
Contract
Communications
TIME
Sequential
Futures

11. Reactive programming
is a programming paradigm
oriented around
data flows
and the
propagation of change

13. CompletableFuture
A Future that may be
explicitly completed
and may trigger actions
upon its completion.

14. Chaining methods
run
thenAccept
thenApply
thenCompose
whenComplete

15. Joining methods
runAfterBoth
thenAcceptBoth
thenCombine
...
allOf

16. Model the flow

18. Customer
Contract
Communications
TIME
Sequential
Futures
Completable Futures

19. Links
● Demo:
https://github.com/martijnblankestijn/reactive-rest-demo
● JAX-RS
● Completable Future
● ManagedExecutor: JSR 236 Concurrency Utilities for Java EE
● Reactive Manifesto