What is a keytab, and how do I use one?
Introduction to Kerberos for Managers
Crash Course to Kerberos
Appendix D. Troubleshooting
JAAS authentication with Kerberos
http://www.roguelynn.com/words/explain-like-im-5-kerberos/
KDC = Kerberos Key Distribution Center
TGT = Ticket Granting Ticket
TGS = Ticket Granting Server

For the configuration below (just a copy from spring security reference):

The file /path/to/krb5.ini could be an exact copy of /etc/krb5.conf from the KDC machine. You'll have to make sure the host names used in krb5.ini's default_realm are accessible for the application.