Servlet Pass Predicate

Use a servlet pass predicate to define which requests should be forwarded to the servlet

In a traditional server setup, you are used to two separate pieces of software

  • A web server like NGinx, Apache, or IIS which serves static files, performs URL rewrites, and proxies some requests off to a servlet

  • A Servlet container like Tomcat or CommandBox receiving the proxied requests on another port (HTTP or AJP) and processing CF code

In CommandBox, now we have the ability to combine both of those bullets together into a single piece of software. No reverse proxy is needed, nor is a second port to proxy to.

In all cases with the legacy setup, there is always a check of some kind that decides which requests will get sent to the servlet. This is usually checking for URLs ending in .cfm or .cfc. Common implementations of this are:

  • Adobe's CF connector

  • The mod_cfml module for Apache

  • BonCode for IIS

  • A custom proxy directive in your web server.

As of CommandBox 6, we have the same setting and it can be set as web.servletPassPredicate which is simply an Undertow Predicate. By default, CommandBox uses the following predicate for the servletPassPredicate:

regex( '^/(.+?\\.cf[cm])(/.*)?$' )

So the URI /index.cfm will get sent to the servlet, but /test.txt would just get sent by the static file resource handler. You can customize this if necessary with any valid Undertow predicate. It can even be different on a per-site basis by setting it inside the sites object or .site.json file for a given site.

# Send ALL traffic to the servlet (the servlet's default handler will serve static files)
server set web.servletPassPredicate=true

# Only serve CF files out of the cgi folder
server set web.servletPassPredicate="regex( '^/cgi/(.+?\\.cf[cm])(/.*)?$' )"

# process CFM files or anything in the /REST/ directory
server set web.servletPassPredicate="regex( '^/(.+?\\.cf[cm])(/.*)?$' ) or path-prefix-nocase( /REST/ )"

Note, be careful as your servlet pass setting may send .cfm files to the static file handler. CommandBox has a failsafe in place to prevent the source code from being returned, but you should still use caution when configuring this.

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