| 1 | package com.reallifedeveloper.common.domain.event; | |
| 2 | ||
| 3 | import java.util.ArrayList; | |
| 4 | import java.util.List; | |
| 5 | ||
| 6 | /** | |
| 7 | * A publisher of domain events that keeps track of subscribers on a per-thread basis. It is assumed that subscription and publishing are | |
| 8 | * done by the same thread, and publishing is handled synchronously. To handle events asynchronously, a subscriber could send a message to a | |
| 9 | * message queue, or store the event for later processing. | |
| 10 | * <p> | |
| 11 | * If threads are reused, it is important to call the {@link #reset()} method to clear any previous subscribers. | |
| 12 | * <p> | |
| 13 | * The normal use-case for this class is as follows: | |
| 14 | * <ul> | |
| 15 | * <li>A request comes in to an application service.</li> | |
| 16 | * <li>The application service creates or retrieves an instance of this class and calls the {@link #reset()} method.</li> | |
| 17 | * <li>The application service registers all necessary subscribers using the {@link #subscribe(DomainEventSubscriber)} method.</li> | |
| 18 | * <li>The application service delegates to domain services or aggregates, which publish events when something interesting happens in the | |
| 19 | * domain, using the {@link #publish(DomainEvent)} method.</li> | |
| 20 | * </ul> | |
| 21 | * | |
| 22 | * @author RealLifeDeveloper | |
| 23 | */ | |
| 24 | public class ThreadLocalDomainEventPublisher implements DomainEventPublisher { | |
| 25 | ||
| 26 | private static ThreadLocal<List<DomainEventSubscriber<DomainEvent>>> subscribers = ThreadLocal.withInitial(ArrayList::new); | |
| 27 | ||
| 28 | private static ThreadLocal<Boolean> publishing = ThreadLocal.withInitial(() -> false); | |
| 29 | ||
| 30 | /** | |
| 31 | * Registers an event handler with this publisher. | |
| 32 | * | |
| 33 | * @param subscriber the event handler to register | |
| 34 | * | |
| 35 | * @throws IllegalStateException if called while publishing events | |
| 36 | */ | |
| 37 | @Override | |
| 38 | public void subscribe(DomainEventSubscriber<? extends DomainEvent> subscriber) { | |
| 39 |
1
1. subscribe : removed call to com/reallifedeveloper/common/domain/event/ThreadLocalDomainEventPublisher::checkPublishing → KILLED |
checkPublishing(); |
| 40 | @SuppressWarnings("unchecked") | |
| 41 | DomainEventSubscriber<DomainEvent> s = (DomainEventSubscriber<DomainEvent>) subscriber; | |
| 42 | subscribers().add(s); | |
| 43 | } | |
| 44 | ||
| 45 | /** | |
| 46 | * Publishes a domain event, i.e., calls the {@link DomainEventSubscriber#handleEvent(DomainEvent)} method for each registered | |
| 47 | * subscriber. | |
| 48 | * | |
| 49 | * @param event the domain event to publish | |
| 50 | * | |
| 51 | * @throws IllegalStateException if called while already publishing events | |
| 52 | */ | |
| 53 | @Override | |
| 54 | public void publish(DomainEvent event) { | |
| 55 |
1
1. publish : removed call to com/reallifedeveloper/common/domain/event/ThreadLocalDomainEventPublisher::checkPublishing → KILLED |
checkPublishing(); |
| 56 | try { | |
| 57 |
1
1. publish : removed call to java/lang/ThreadLocal::set → KILLED |
publishing.set(true); |
| 58 | for (DomainEventSubscriber<DomainEvent> subscriber : subscribers()) { | |
| 59 |
1
1. publish : negated conditional → KILLED |
if (subscriber.eventType().isAssignableFrom(event.getClass())) { |
| 60 |
1
1. publish : removed call to com/reallifedeveloper/common/domain/event/DomainEventSubscriber::handleEvent → KILLED |
subscriber.handleEvent(event); |
| 61 | } | |
| 62 | } | |
| 63 | } finally { | |
| 64 |
1
1. publish : removed call to java/lang/ThreadLocal::set → KILLED |
publishing.set(false); |
| 65 | } | |
| 66 | } | |
| 67 | ||
| 68 | /** | |
| 69 | * Removes all subscribers. Since subscribers are stored on a per-thread basis, and since threads may be reused, this method should be | |
| 70 | * called when starting to handle a new request. | |
| 71 | * | |
| 72 | * @throws IllegalStateException if called while publishing events | |
| 73 | */ | |
| 74 | public void reset() { | |
| 75 |
1
1. reset : removed call to com/reallifedeveloper/common/domain/event/ThreadLocalDomainEventPublisher::checkPublishing → KILLED |
checkPublishing(); |
| 76 |
1
1. reset : removed call to java/util/List::clear → KILLED |
subscribers().clear(); |
| 77 | } | |
| 78 | ||
| 79 | private List<DomainEventSubscriber<DomainEvent>> subscribers() { | |
| 80 |
1
1. subscribers : replaced return value with Collections.emptyList for com/reallifedeveloper/common/domain/event/ThreadLocalDomainEventPublisher::subscribers → KILLED |
return subscribers.get(); |
| 81 | } | |
| 82 | ||
| 83 | private void checkPublishing() { | |
| 84 |
1
1. checkPublishing : negated conditional → KILLED |
if (publishing.get()) { |
| 85 | throw new IllegalStateException("Method should not be called while publishing events"); | |
| 86 | } | |
| 87 | } | |
| 88 | } | |
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