事件驱动架构模式【其他模式】

事件驱动架构模式

public class EventDriven {
    /**
     * 事件驱动架构模式：
     * Send and notify state changes of your objects to other applications
     * using an Event-driven Architecture.
     * 使用事件驱动的架构来发送通知【此对象状态的变更】给应用程序中的其他组件，解耦了事件源和事件处理器。
     */
    @Test
    public void all() {
        final EventDispatcher eventDispatcher = EventDispatcherImpl.builder().build();
        eventDispatcher.register(UserCreateEvent.class, new UserCreateHandler());
        eventDispatcher.dispacher(UserCreateEvent.of(User.of(Long.valueOf(1), "zxd")));
    }
}

/**
 * 1）事件抽象
 */
interface Event {
    Class<? extends Event> type();
}

abstract class BaseEvent implements Event {
    @Override
    public Class<? extends Event> type() {
        return getClass();
    }
}

/**
 * 2）事件处理器抽象
 */
interface EventHandler<T extends Event> {
    void handle(T event);
}

/**
 * 3）事件调度器抽象
 */
interface EventDispatcher {
    <E extends Event> void register(Class<? extends Event> type, EventHandler<E> hanlder);

    <E extends Event> void dispacher(E event);
}

/**
 * 4）事件调度器实现
 */
@Slf4j
@Builder
class EventDispatcherImpl implements EventDispatcher {
    @Default
    private final ConcurrentMap<Class<? extends Event>, EventHandler<? extends Event>> HANDLERS = new ConcurrentHashMap<>();

    @Override
    public <E extends Event> void register(Class<? extends Event> type, EventHandler<E> hanlder) {
        HANDLERS.putIfAbsent(type, hanlder);
    }

    @Override
    public <E extends Event> void dispacher(E event) {
        final EventHandler<E> handler = (EventHandler<E>) HANDLERS.get(event.getClass());
        if (handler != null) {
            handler.handle(event);
        } else {
            log.error("no handler for event {}", event);
        }
    }
}

@Value(staticConstructor = "of")
class User {
    private Long id;
    private String name;
}

/**
 * 5）具体的事件
 */
@Value(staticConstructor = "of")
class UserCreateEvent extends BaseEvent {
    private User user;
}

/**
 * 6）具体的事件处理器
 */
@Slf4j
class UserCreateHandler implements EventHandler<UserCreateEvent> {
    @Override
    public void handle(UserCreateEvent event) {
        log.info("id:{} name:{}", event.getUser().getId(), event.getUser().getName());
    }
}