I have scanned through the internet and also stackoverflow and I'm still not sure of the purpose of proxypass and proxypassreverse.
Why do we need proxypass (instead of using mod_jk) for apache server to connect to tomcat?
Nice link on SO:: apache to tomcat: mod_jk vs mod_proxy
1.One reason can be to use mod_proxy to include other servers while maintaining fancy URLs.
2.Other advantage can be that when you are using tomcat as server, the mod_proxy_ajp module has the ProxyPassReverseCookiePath directive, which allows you to map the session cookies of a Tomcat web application (other than the root application) into the root of a virtual host.
3.Mod_proxy simply redirects requests for certain URLs to another web server, so it typically requires no additional configuration on the application server.
Also, see http://www.humboldt.co.uk/2009/02/the-mystery-of-proxypassreverse.html