StandardMessenger.java 文件源码

public Set<PluginMessageListenerRegistration> getIncomingChannelRegistrations(Plugin plugin, String channel) {
    if (plugin == null) {
        throw new IllegalArgumentException("Plugin cannot be null");
    }
    validateChannel(channel);

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

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

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

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