StandardMessenger.java 文件源码

public Set<String> getIncomingChannels(Plugin plugin) {
    if (plugin == null) {
        throw new IllegalArgumentException("Plugin cannot be null");
    }

    synchronized (incomingLock) {
        Set<PluginMessageListenerRegistration> registrations = incomingByPlugin.get(plugin);

        if (registrations != null) {
            Builder<String> builder = ImmutableSet.builder();

            for (PluginMessageListenerRegistration registration : registrations) {
                builder.add(registration.getChannel());
            }

            return builder.build();
        } else {
            return ImmutableSet.of();
        }
    }
}