Java Development Tools

Hey guys,

I'm trying to develop this example: http://www.oracle.com/technetwork/developer-tools/adf/learnmore/59-table-filter-by-data-range-176653.pdf in OEPE with a few variations. Since I don't want to use databases I dynamically create a table via a managed bean. That table has 4 columns but only the first one named "Id" is relevant to my problem. The java classes I've created so far are:
"TableRow": Represents a single row containing 4 columns
"TableController": This class is my managed bean for the table itself. It dynamically creates the table content und has 1 getter and 1 setter method for the list of TableRow's created to access them later in the .jspx page.
"QueryEventListener": This class is also a managed bean and should use the filter described in the tutorial above in its "onQuery(QueryEvent event)" method.

I've even created 3 classes that extend "ViewObject", "ViewObjectImpl" and "ViewUsageImpl" as in the JDeveloper example but I think I must have missed a few lines in a .xml file since my onQuery-Method is called but the "MethodExpression.invoke"-method throws a NullPointerEception. (All parameters of the invoke method are != null).

Did anyone of you try to use this tutorial in OEPE and how did you make it work?

Any help is appreciated