This week's book giveaway is in the General Computing forum. We're giving away four copies of Arduino in Action and have Martin Evans, Joshua Noble, and Jordan Hochenbaum on-line! See this thread for details.
Where you have placed the JDBC Driver jar file? If they are at tomcat common/lib then this kind of problem may happen. Try to put a copy of the driver jar file and commons-dbcp.jar file at WEB-INF/lib of your application. Hope this will help.