The test doesn't mention that the UserDirectory source code is available in the download. The following should be added as the second paragraph of page 20:
"We will also focus only on the Struts source files you need to create. For example, the UserDirectory class is part of the application's business logic. The Struts framework interacts with this class, but the UserDirectory is not part of the Struts layer. (You would need this class whether you used Struts or not.) If you are interested, the source code for UserDirectory is provided in the WEB-INF/classes folder of the register application."