How to prevent direct ip address

[Jaakko Taipale]

I have specified domain eg. www.myapp.com and I have tomcat running my
machine that have IP address 123.123.123.123. Now I can access to my app
with two address:
 
http://www.myapp.com/myapp or
http://123.123.123.123/myapp
 
How can I prevent tomcat to response when somebody is trying to access with
direct ip?
 
--
Jaakko