Policy Action -Update Custom Asset Problem-

Hi all,
İ am trying to update my custom asset at change lifecycle or pre-post update-create. i have a slot its type String and read only in my custom asset. i want to write who create the asset information to this slot value. i created a Java project and an action class. i created different package in this project and i put there my custom asset object which mapped with CSAF. i used my asset object in execute methot. i followed the documentation for create custom action and achive to do custom action. When i try to use this action occuring exception “java.lang.IllegalArgumentException: interface package.mymodel.ServisModel is not visible from class loader” so i cant update my custom asset ? Can anybody help me?