Java - Scheduler holt Daten vom externen System ab und stellt sie für Dienste zur Verfügung ⇐ Java

[Anonymous]

Ich brauche einen Scheduler, der Daten von einer externen Quelle abruft und versucht, sie regelmäßig zu aktualisieren.
Es ist nicht bekannt, wenn die externen Daten zunächst verfügbar sind. Deshalb gibt GetCurrentData eine Zukunft zurück.

Code: Select all

@Slf4j
public class ScheduledProvider {

private static final Random RANDOM = new Random();

private final List futures = new ArrayList();

private final AtomicReference currentData = new AtomicReference();

public ScheduledProvider() {
final NamedThreadFactory namedThreadFactory = new NamedThreadFactory("scheduled-provider", (t, e) -> log.warn("Caught exception", e));
final ScheduledExecutorService scheduledExecutor = Executors.newSingleThreadScheduledExecutor(namedThreadFactory);
scheduledExecutor.scheduleAtFixedRate(this::tick, 1, 1, TimeUnit.SECONDS); // Simulate not initially available data by setting the initialdelay to 1 second
}

/** Prevent an exception to stop the scheduler */
private void tick() {
try {
updateData();
} catch (final Throwable t) {
log.warn("Swallow throwable", t);
}
}

private void updateData() {
final List list = List.of(getRandomIntBetween1And10(), getRandomIntBetween1And10(), getRandomIntBetween1And10());
log.info("Calculated new list={}", list);
final GatheredData newData = new GatheredData(list);
currentData.set(newData);
synchronized (futures) {
futures.forEach(future -> future.complete(newData));
futures.clear();
}
}

private int getRandomIntBetween1And10() {
return RANDOM.nextInt(10) + 1;
}

public CompletableFuture getCurrentData() {
final GatheredData data = currentData.get();
if (data != null) {
return CompletableFuture.completedFuture(data);
}
log.info("Data is loading...");
final CompletableFuture future = new CompletableFuture();
synchronized (futures) {
futures.add(future);
}
return future;
}

}