Virtually all J2EE servlet containers come bundled with an HTTP server, and setting one of them up is usually very simple. Despite the conveniece, I've found many reasons not to use these bundled HTTP servers in even a development/testing environment. In production, the decision is simple: the Apache HTTPD server is faster, more stable, more secure, more configurable and more powerful than any bundled HTTP server. In development and testing, I've found the configurability of Apache to be an enormous asset, offsetting the additional challenge of using mod_jk to link Apache and the servlet container.

Downloading mod_jk

The mod_jk package is closely connected to the development of Jakarta Tomcat, and can be downloaded most easily by finding a tomcat mirror site. From the Tomcat site, make your way to a download mirror (via the download links), and then browse to jakarta/tomcat-connectors/jk/binaries/ once inside the mirror (paths may be slightly different due to mirror uniquenesses). From the binaries directory for your platform, download the newest version of mod_jk that matches your Apache version. Note that there are separate packages for the Apache 1.x and 2.x release cycles.

Placing the Module

After downloading the .so file, you'll need to place it in your Apache modules directory. Rename the file mod_jk.so and place it in %APACHE_ROOT%/modules.

Notifying Apache

Create a file d:/www-config/mod_jk-apache.conf, and place the following statements in it.



LoadModule jk_module "modules/mod_jk.so"


#
# Standard mod_jk mappings
#
JkMount /*.jsp java1
JkMount /servlet/* java1
JkUnMount /servlet/*.gif java1


That file is imported using the Apache configuration recommended in another post, where Apache's httpd.conf includes all .conf files in d:/www-config. Note: the documentation for mod_jk directives is available.

The workers.properties file referenced above is a listing of "workers" (instances of a Java servlet container). Create the file d:/www-config/mod_jk-workers.properties.


worker.list=java1

worker.java1.port 8009
worker.java1.host localhost
worker.java1.type ajp13


The complete chain works like this: 1) The Apache JkMount and JkUnmount directives tell Apache which request patterns to forward on to the servlet container by its "worker" name. 2) The servlet container with the worker name in question receives the request as if it came directly from the client computer. 3) The servlet container's response is retrieved by Apache and returned to the end user. The trick is that only portions of the hosting tree are mapped to Java. Ideally, static HTML, Javascript, CSS and images are handled by Apache directly, without having to consult the servlet container.