Very hazardous. Looking at the generated Java code will give you some answers (I think so). In fact, accessing to some objects properties is possible (there is blogs and articles about this) but changing anything seems to be dangerous (IMHO).
You don't have total control over other components at runtime, but you can take some control. An example of this is switching Connections (DB and FTP, for example) at runtime. This tutorial shows how this is achieved by using Java (https://www.rilhia.com/quicktips/quick-tip-dynamically-change-db-connection). As @TRF suggests, it is not necessarily the safest thing to be trying. But sometimes it can actually be quite useful. However this is not really documented anywhere and would probably be considered "hacking". Remember to look at the code that is generated. If you can read Java, you will learn a lot.
