YSlow and Cache-Headers

If you run YSLow on one of your web applications, you can obtain some really useful information about improving the performance of your application. One common performance improvement is to set expiration headers on static resources (such as CSS, JS and image files). Setting this header, will help preserve the file in the browser cache, thus preventing reload of the image on subsequent page refreshes. Web servers like Apache make this easy (with a configuration file change). However, if you are using Tomcat both as a Web server and application container, the solution here is relative easy, but requires some coding. To facilitate this in Tomcat, you need to create a ServletFilter to add the Cache-Control header to the response, and then register your filtered types in your web.xml. A blog on this was posted by Byron Tymvios on jGuru here.