If you want to use this as frontend for a Tomcat or JBoss with embedded tomcat, you need to install mod_jk.
The canonical way is to use the macports port. Unfortunately will this a) try to install apache2 and b) fail building (at least for me).
Fortunately there is a blog entry out there that explains how to do it by hand.
Note, that the link to the apache download is outdated. The best is to go to the root of the dowloads and just download the latet version.
When you are using mo_jk in front of a embedded tomcat in JBossAS, you also don't need the workers.tomcat_home directive in the config file.
Ah, and when this works, don't forget to trim down the loglevel in httpd.conf from trace to info. Else you will end up with gigabytes of logs.