Apache: Setting the Content-Disposition Header with mod_rewrite

Following yesterday's post on serving up static content with Restlet's built in web-server, I received a couple of questions on Twitter inquiring how I implemented my "download the latest Cappuccino" feature at http://mark.koli.ch/cappuccino/latest.  If you visit http://mark.koli.ch/cappuccino/latest you'll notice it prompts you to save a file named "cappuccino.jar", which is the latest Cappuccino build available on kolich.com.  Even if I change versions, and post a newer build on my server, you can always download the latest from http://mark.koli.ch/cappuccino/latest.  So, you might expect this URL to prompt you to save a file named "latest", given that this is how most web-browsers work; they take the string following the last / and use that as the file name.  However, when someone visits /latest I want the browser to prompt them to save "cappuccino.jar" and not "latest".

The title of this post is slightly misleading, since the Content-Disposition header cannot be set directly using mod_rewrite.  As I understand it, there are a set of headers that mod_rewrite understands, and Content-Disposition is not one of them.

So, to prompt the user to save cappuccino.jar instead of "latest", I used an interesting combination of mod_rewrite and mod_headers.  Specifically, I used mod_rewrite to internally redirect any requests to .../cappuccino/latest to the latest cappuccino Jar file available on my server.  Second, I used mod_headers to add a Content-Disposition header to any request ending with ../cappuccino/latest, which forces the browser/client to interpret the file as "cappuccino.jar" and not "latest".  Here's the configuration from my Apache httpd.conf file:

## Internally redirect for Cappuccino
RewriteRule ^/cappuccino/latest /cappuccino/dist/cappuccino-v0.1.jar [L]
SetEnvIfNoCase Request_URI cappuccino\/latest$ cappuccino-latest
Header set Content-Disposition \
    "attachment; filename=cappuccino.jar" env=cappuccino-latest

With this configuration, Apache will set the Content-Disposition header on each request for http://mark.koli.ch/cappuccino/latest.  Using a tool like HttpFox, you can prove to yourself that this works as expected:




Enjoy.