Determining Absolute Path in a Web Application

I was looking at the NetBeans EE forums, and someone asked how to determine the path in a web application. This is a common question so I thought I would provide two examples. The first is a servlet which returns the absolute path to the web application root. The other is a JSF application that does the same thing, and lists the files.
Note: The code is based on Java EE 6.

PathServlet.java

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DirectoryLister.java

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index.xhtml

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