Justin Dunham

I recently had the need to do some client side file caching for static files and images. Not usually a problem, just setup IIS to expire after X days for that directory. But for this site profile images were stored in the database, so coldfusion would have to control the cache headers on image render.

I attached the code for imageRender.cfm which adds two headers

< cfheader
name="Expires"
value="#GetHttpTimeString(dateadd('d', 30, Now()))#"
/>
< cfheader
name="Last-Modified"
value="#GetHttpTimeString(qry_imageRender.lastModified)#"
/>


The render page then does a check to see if the file has been modified before it outputs the file to the client and if it can sends a not modified header. This saves quite a bit of server traffic and as a result lowers the load time for a typical page view on the site.

This could work for any type of page but especially helpful when serving images or other large static files. Hope this helps someone, as most of my initial google searches showed how to not cache a script.