ofNode in ParameterGroup

Hello People,
I´m looking for a way to save my class parameters in a JSON-File. For dynamical reasons I try to make them all ofParamters and put them in a group. Is there a way to include the ofNode in a similar way? I saw that node.position, node.orientation, node.scale are ofParamters but private members. Making them public could cause other problems, is there a general solution for that? Thanks ahead!