Intercept.java

public interface InterceptHandler {
    InterceptEnum beforePublish(ProtocolEvent evt, InterceptContinue continuation);
    InterceptEnum beforeSubscribe(ProtocolEvent evt, InterceptContinue continuation);
    InterceptEnum beforeConnect(ProtocolEvent evt, InterceptContinue continuation);
    
    void onConnect(ConnectMessage msg);
    void onPublish(PublishMessage msg);
    void onSubscribe(SubscribeMessage msg);
    void onUnsubscribe(SubscribeMessage msg);
}

public enum InterceptEnum {
    CONTINUE,
    BREAK,
}

public interface InterceptContinue {
    void doContinue(ProtocolEvent evt);
}