Apache Tomcat is the standard “reference implementation” of the
Java Servlet APIs. A web-server written in Java, Tomcat was used to test the Servlet, Groovlet, JSP and GSP examples in the lecture course. Grails comes with its own built-in web server, so Tomcat is not needed for the project but might be considered if you were to develop and deploy a real Web Application in Java, Groovy or Grails. I used the latest version 6 (which requires Java 1.5) for the examples.