The mod_proxy_ajp module for Apache has many advantages over mod_jk for connecting a Tomcat server to an Apache front. For me, the crucial advantage was the ProxyPassReverseCookiePath directive, which allows me to map the session cookies of a Tomcat web application (other than the root application) into the root of a virtual host.

Unfortunately, many tutorials contain misleading advice, and recommend this pattern for the ProxyPassReverse, which will break if the web application issues a redirect:

ProxyPass /jspdir ajp://localhost:8009/jspdir
ProxyPassReverse /jspdir ajp://localhost:8009/jspdir