Web library projects allow you to associate Java™ projects
with "virtual" JAR files in a Web project's WEB-INF/lib directory. You can
reference JAR files that exist elsewhere in the Enterprise Application project
that contains your Web project, if they are in the Web project's build path,
and avoid the need to explicitly copy these JAR files into the project's lib
folder before you publish the Web application to a server.
To set up