URL masking in Apache Tomcat 5.5

Hi,

at my office we have a web application installed on an Apache Tomcat
5.5.
Is there a way to mask the url to a subsite in Tomcat?

Example:
site adress: http://10.10.10.10/application/servlet/APP?wp=EN
and subsite http://app.example.com

I want the subsite adress to open the site and keeping the subsite
adress
all the time. So if I work in the web application the adress should
always be
http://app.example.com. Is this possible?

regards

Mikael