How can I force a cached css file to be reloaded on a JSP (i.e. not PHP)?

Question

I am altering a css file which will make drastic changes to my site. Is there a way to force the clients to reload the css so that they pick up the new changes. Unfortunately asking thousands of people to CTRL + F5 or clear their cache isn't an option. I read on a couple of blogs about appending todays date on the css filename as a parameter would work.

Answer 1

You can add a unique query string parameter on to the end of the css file url

<link rel="stylesheet" type="text/css" href="/my/css/file.css?123" />

Just increment the number each time you make an update.

EDIT:

To load it from the web.xml file use the following:

<link rel="stylesheet" type="text/css" href="/my/css/file.css?<%=application.getInitParamer("cssBuildNumber")%>" />

and this in web.xml

<context-param>
   <param-name>cssBuildNumber</param-name>
   <param-value>123</param-value>
</context-param>