How to configure mod_proxy_ajp with Tomcat ?

mod_proxy_ajp is an Apache module which can be used to forward a client HTTP request to an internal Tomcat application server using the AJP protocol.

To respond to the question "Why should I use mod_proxy_ajp rather than a classic mod_proxy ?", here is a small recap:

• You can gain a lot of flexibility (lot of the apache modules/features can be used especially "name-based virtual hosting")
• Practical for those who need to support Java applications along with PHP / Perl … (only one apache server is needed)
• Certificates management is easier in apache configuration (this argument is a lot subjective)
• It's not Tomcat's main objective to serve http static resources (not optimized for that)
• Load balancing/cluster management is easier with an apache frontend

You just have to create the AJP connector in the conf/server.xml file like that:

<Connector port="8009" enableLookups="false" redirectPort="8443" protocol="AJP/1.3" />

This line will enable AJP connections to the 8009 port of your tomcat server (localhost for example).

One way (useful if this apache is a global front end) is to create a virtual host for this application.

Listen 1979
NameVirtualHost *:1979
<VirtualHost *:1979>
   ServerName localhost
   ErrorLog /var/log/apache2/ajp.error.log
   CustomLog /var/log/apache2/ajp.log combined
 
   <Proxy *>
     AddDefaultCharset Off
     Order deny,allow
     Allow from all
   </Proxy>
 
   ProxyPass / ajp://localhost:8009/
   ProxyPassReverse / ajp://localhost:8009/
</VirtualHost>

• ProxyPass and ProxyPassReverse are classic reverse proxy directives used to forward the stream to another location.
• ajp://... is the AJP connector location (your tomcat's server host/port)

A web client will connect through HTTP to http://localhost:1979/ (supposing your apache2 server is running on localhost), the mod_proxy_ajp will forward you request transparently using the AJP protocol to the tomcat application server on localhost:8009.