javaFx事件总线EventBus示例

管理事件的订阅和发布 示例（1）

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import java.util.function.Consumer;
public interface EventBus {

  /**
     * 订阅事件类型。
     *
     * @param eventType 事件类型，可以是所有要订阅的事件的超类。
     * @param subscriber 将消耗事件的 subscriber。
     * @param <T> 事件类型类。
     */
    <T extends Event> void subscribe(Class<? extends T> eventType, Consumer<T> subscriber);

    /**
     * Unsubscribe from all event types.
     *
     * @param subscriber the subscriber to unsubscribe.
     */
    <T extends Event> void unsubscribe(Consumer<T> subscriber);
/**
     * 取消订阅事件类型。
     *
     * @param eventType 为事件类型，可以是所有要退订的事件的超类。
     * @param subscriber 订阅者 取消订阅。
     * @param <T> 事件类型类。
     */
    <T extends Event> void unsubscribe(Class<? extends T> eventType, Consumer<T> subscriber);

  /**
     * 向所有订阅者发布事件。
     *
     * <p>事件类型是<code>事件</code>的类。该事件将发布到订阅了
     * 此事件类型或任何超类。
     *
     * @param事件。
     */
    <T extends Event> void publish(T event);

}

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import java.util.Map;
import java.util.Objects;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArraySet;
import java.util.function.Consumer;

public final class DefaultEventBus implements EventBus {

    private final Map<Class<?>, Set<Consumer<?>>> subscribers = new ConcurrentHashMap<>();
    private DefaultEventBus() {}

    @Override
    public <E extends Event> void subscribe(Class<? extends E> eventType, Consumer<E> subscriber) {
        Objects.requireNonNull(eventType, "事件类型不能为 null");
        Objects.requireNonNull(subscriber, "订阅者不能为 null");
        Set<Consumer<?>> eventSubscribers = getOrCreateSubscribers(eventType);
        eventSubscribers.add(subscriber);
    }

    private <E> Set<Consumer<?>> getOrCreateSubscribers(Class<E> eventType) {
        return subscribers.computeIfAbsent(eventType, k -> new CopyOnWriteArraySet<>());
    }

    @Override
    public <E extends Event> void unsubscribe(Consumer<E> subscriber) {
        Objects.requireNonNull(subscriber, "订阅者不能为 null");

        subscribers.values().forEach(eventSubscribers -> eventSubscribers.remove(subscriber));
    }

    @Override
    public <E extends Event> void unsubscribe(Class<? extends E> eventType, Consumer<E> subscriber) {
        Objects.requireNonNull(eventType, "事件类型不能为 null");
        Objects.requireNonNull(subscriber, "订阅者不能为 null");

        subscribers.keySet().stream()
                .filter(eventType::isAssignableFrom)
                .forEach(type -> subscribers.get(type).remove(subscriber));
    }

    @Override
    public <E extends Event> void publish(E event) {
        Objects.requireNonNull(event, "事件不能为空");

        Class<?> eventType = event.getClass();
        subscribers.keySet().stream()
                .filter(type -> type.isAssignableFrom(eventType))
                .flatMap(type -> subscribers.get(type).stream())
                .forEach(subscriber -> publish(event, subscriber));
    }

    @SuppressWarnings("unchecked")
    private <E extends Event> void publish(E event, Consumer<?> subscriber) {
        try {
            ((Consumer<E>) subscriber).accept(event);
        } catch (Exception e) {
            Thread.currentThread().getUncaughtExceptionHandler().uncaughtException(Thread.currentThread(), e);
        }
    }

    // Singleton instance
    private static class InstanceHolder {
        private static final DefaultEventBus INSTANCE = new DefaultEventBus();
    }

    public static DefaultEventBus getInstance() {
        return InstanceHolder.INSTANCE;
    }
}

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public final class BrowseEvent extends Event {

    private final URI uri;

    public BrowseEvent(URI uri) {
        this.uri = uri;
    }

    public URI getUri() {
        return uri;
    }

    @Override
    public String toString() {
        return "BrowseEvent{"
            + "uri=" + uri
            + "} " + super.toString();
    }

    public static void fire(String url) {
        Event.publish(new BrowseEvent(URI.create(url)));
    }
}

管理事件的订阅和发布 示例（2）
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