Java EE Cache Filter

In my current web project I was having some performance issues, I needed a tool that allowed me to do some testing so I can see what’s wrong and what I can do better so my application perform faster.

My search lead me to High Performance Web Sites and YSlow, a very good talk by Steve Souders the Chief Performance Yahoo! at Yahoo!

YSlow is an easy-for-use plugin that allows you to inspect any web page just clicking a button.

YSlow analyzes web pages and tells you why they’re slow based on the rules for high performance web sites. YSlow is a Firefox add-on integrated with the popular Firebug web development tool. YSlow gives you:

• Performance report card
• HTTP/HTML summary
• List of components in the page
• Tools including JSLint

A good way to reduce the number of Http Connections required to load a web page is to store images and other resources in the browser cache.

Expires is a HTTP header that allows you to define when a resource (image, css, javascript, …) will need to be reloaded. It is a String representation of a Date in the format EEE, dd MMM yyyy HH:mm:ss z. Cache-Control response headers give Web publishers more control over their content and address the limitations of Expires.

To correctly produce these headers I implemented a Java cache filter. Check out the project on GitHub at samaxes/javaee-cache-filter or read the docs on the wiki.

Sample configuration:

<!-- Declare the filter in your web descriptor file `web.xml` -->

<filter>
    <filter-name>imagesCache</filter-name>
    <filter-class>com.samaxes.filter.CacheFilter</filter-class>
    <init-param>
        <param-name>expiration</param-name>
        <param-value>2592000</param-value>
    </init-param>
</filter>

<filter>
    <filter-name>cssCache</filter-name>
    <filter-class>com.samaxes.filter.CacheFilter</filter-class>
    <init-param>
        <param-name>expiration</param-name>
        <param-value>604800</param-value>
    </init-param>
    <init-param>
        <param-name>vary</param-name>
        <param-value>Accept-Encoding</param-value>
    </init-param>
</filter>

<filter>
    <filter-name>jsCache</filter-name>
    <filter-class>com.samaxes.filter.CacheFilter</filter-class>
    <init-param>
        <param-name>expiration</param-name>
        <param-value>216000</param-value>
    </init-param>
    <init-param>
        <param-name>private</param-name>
        <param-value>true</param-value>
    </init-param>
</filter>

<!-- Map the filter to serve your static resources -->

<filter-mapping>
    <filter-name>imagesCache</filter-name>
    <url-pattern>/img/*</url-pattern>
</filter-mapping>

<filter-mapping>
    <filter-name>cssCache</filter-name>
    <url-pattern>*.css</url-pattern>
</filter-mapping>

<filter-mapping>
    <filter-name>jsCache</filter-name>
    <url-pattern>*.js</url-pattern>
</filter-mapping>