So, this is kinda like saying "I need to be able to drink
coffee while driving a car. I know how to drink coffee. Can you teach me how to drink coffee while driving a car?" Sure, you can do both at the same, but you've got to focus one one at a time, and when you get a handle on both, do them both at the same time.
You can learn hibernate completely independent of Tomcat or any
Servlet engine. When you understand Hibernate, and you also understand Servlet development, you'll find it very easy to pull them together.
Focus on some simple Hibernate tutorials. Here's a few tutorials I put together that are very easy to understand and step through:
Learning Hibernate
Good luck!
-Cameron McKenzie