The "Nested controllers" example in http://docs.oracle.com/javase/8/javafx/api/javafx/fxml/doc-files/introduction_to_fxml.html#nested_controllers should clearly say that the injection point variable annotated with @FXML in fact must end be named following the pattern "fx:id" + "Controller".

It is confusing to FXML beginners that there is a convention existing about the name's "Controller" suffix which in fact is not told anywhere in that document other than an an example.