App Module's method return type and parameters must implement java.io.Serializable to be exposed

If you want to expose a app modules method, then it's return type and parameters must implement java.io.Serializable.
Otherwise the wizard we used to expose the method  does not even show it.

 If you know that the Class of the return type and parameters of your method's  can be Serializable, then add "implements Serializable"  in the class declaration to continue.