As I had to some pages to get this information together, here’s to to set up a single tomcat webapp as the root of an apache server (on Debian, but should work similarly on other systems).
Assuming you’re configuring the server for the domain abc123.com
Setup your tomcat whereever you like. Per default, it already has the necessary AJP connector configured on port 8009.
In order for your webapp to be the root webapp, delete the existing ROOT directory, and rename your war file to ROOT.war and put it in the webapps directory, then start Tomcat. That’s it for Tomcat.
For the Apache configuration (being root), go to /etc/apache2/sites-available, create a file named abc123.com (yes, .com not .conf. But abc123.com.conf might work too) and put the following in it
<VirtualHost *:80> ServerName abc123.com ServerAlias *.abc123.com ProxyPreserveHost on ProxyRequests off ProxyPass / ajp://localhost:8009/ ProxyPassReverse / ajp://localhost:8009/ </VirtualHost>
and run
a2ensite abc123.com a2enmod proxy_ajp service apache2 restart
After this, you webapp should be available at abc123.com