Want to use reflection still work as it is eventhough the class is renamed

I store a fully qualified class name in a file. Let say in a xml file: mypackage.myclass

Then, somehowe refactoring is needed to change the package name. The new name is mynewpackage.myclass.

How can I still read the existing files because I dont want to change those files? What is the work around or is there any OO pattern that can be used here?

Thanks.