Sun Java System Web Server 7.0 Update 4 Developer's Guide to Java Web Applications

key-field Element

Specifies a component of the key used to look up and extract cache entries. The web container looks for the named parameter, or field, in the specified scope.

If this element is not present, the web container uses the Servlet Path, the path section that corresponds to the servlet mapping that activated the current request. See the Servlet 2.5 specification, section SRV 4.4, for details on the Servlet Path.