External resources can be plugged in to our web applications in a theme style typical by the portal systems. We can include additional themes included inside JAR files in the WEB-INF/lib directory of our war, and they can automatically be used by the web application. So, as an example, we can create a JAR file containing the following files:

Now zip it in a JAR file, put in the WEB-INF/lib of our web application, and deploy the web application. Now we are able to read the styles.css inside the context root of the web application:
