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11.12.07
Application.cfc Methods & Example Uses
By Raymond Camden
A reader commented yesterday that my Application.cfc reference doesn't really say how to use the various methods.
Since my reference is intended to be a simple code skeleton, I thought I'd quickly explain each of the methods and possible uses for them. Using my skeleton as a guide, let's cover the methods in order.
onApplicationStart
This method is run when the application starts up. Anything you want to define once in the life cycle of your application should be defined here. Typically this is where you will set your Application variables:
onApplicationEnd
This method is run when the application ends. You could use it for logging. Frankly, I've never used it. It's nice that it is there and all, but I haven't had a practical need for it. Since every hit will reset the application time out, and applications only timeout after two hours, only a site with minimal traffic will ever even run this.
It is important to remember that you can cannot use the Application scope here. The application is over, remember? ColdFusion passes a copy of the Application scope to the method though and you can introspect that.
onMissingTemplate
Now this is a nice one. This method is run when a request for a CFM results in a file not found. ColdFusionBloggers.org uses this. For a full blog entry on it, see: onMissingTemplate Example
onRequestStart
This method is run before your request begins. You could use it to include a header, but I think this is a bad idea. I wouldn't mix display code inside your Application.cfc. Also - there may be cases where you don't want a header (like a CFM file that returns XML or JSON). You could use it to cfinclude a UDF library. Thing is - you don't have access to the Variables scope of your page here. So if you do use this method to include a UDF library, be sure to copy your UDFs into the request scope. That's something I like to do anyway since it allows me to call the UDFs from custom tags if I need them.
onRequest
This is run when the request ends. You may be tempted to do a footer here - but again, I'd recommend against it. Honestly, I've never found a real good use for this. You could use it to log a user's "path" through your system:
Continue reading this article.
About the Author:
Raymond Camden, ray@camdenfamily.com
http://ray.camdenfamily.com
Raymond Camden is Vice President of Technology for roundpeg, Inc. A long
time ColdFusion user, Raymond has worked on numerous ColdFusion books
and is the creator of many of the most popular ColdFusion community web
sites. He is an Adobe Community Expert, user group manager, and the
proud father of three little bundles of joy.
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