guava的@Subscribe的synchronized问题

[MingJunDuan]

Hi，你好，提个问题，guava的EventBus.register()注册时，会最终调用Subscriber.create()方法，如下，会判断方法上是否有AllowConcurrentEvents注解，来创建不同的Subscriber，如果没有AllowConcurrentEvents注解则创建SynchronizedSubscriber，而这个类的invokeSubscriberMethod方法中使用了synchronized作为同步，所以如果只是加上注解Subscribe在方法上，那么非真正的并发.

...
    static Subscriber create(EventBus bus, Object listener, Method method) {
        return (Subscriber)(isDeclaredThreadSafe(method) ? new Subscriber(bus, listener, method) : new Subscriber.SynchronizedSubscriber(bus, listener, method));
    }
...
    private static boolean isDeclaredThreadSafe(Method method) {
        return method.getAnnotation(AllowConcurrentEvents.class) != null;
    }

    @VisibleForTesting
    static final class SynchronizedSubscriber extends Subscriber {
        private SynchronizedSubscriber(EventBus bus, Object target, Method method) {
            super(bus, target, method, null);
        }

        void invokeSubscriberMethod(Object event) throws InvocationTargetException {
            synchronized(this) {
                super.invokeSubscriberMethod(event);
            }
        }
    }
...

[HaojunRen]

Nepxion Eventbus只是对Guava做了易用性的封装

[MingJunDuan]

了解