Generate mapping files from pre-existing POJO java files

Hello Experts,

I am looking forward for a way to generate mapping files from pre-existing JAVA classes. JAVA files for these classes don’t have any annotations, but they have some kind of hierarchy.
I know that it is possible to generate mapping files from DB tables, but I don’t have any pre-existing DB tables, but would like to create them using mapping file.

Thanks,
Kailas