Welcome to the JavaRanch, Anila! I've split your question out to a
thread of its own so that people won't get confused.
I have not worked with Tomahawk in a while, but tree controls often allow selecting more than one node at a time. Selection isn't a Model data attribute normally, it's part of the View State, just like being expanded/collapsed. So you'd need to capture that state someplace that the backend logic can know about it. Either by querying the control or by putting in support logic, such as adding a "selected" flag to the tree node model object and toggling it with a selection listener.
Don't forget that in HTTP systems such as
JSF, a listener event isn't a real-time event unless it's wired to an AJAX control. A listener listens when the form is submitted, not when people click on and off on the webpage.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.