Use Annotation Processor

[KangoV]

Using annotation processors at compile time would simplify the whole process and you could also immediately see changes in the generated code in your ide.

For example:

@Passport(link="libforeign")
public interface Linked {
   int string_length(String s);
   double sumArrD(double[] arr, int count);
}

Styles could be added to modify how the generated class is named etc. See how styling is implemented in the Immutibles library as an example to how this could be achieved.