 <p>AFAIK T4CConnection should implement oracle.jdbc.OracleConnection. IMHO you have 2 driver implementation, one on the app server and one in your project dependencies, there must be a classloading issue as the retrieved driver implementation is loaded by the shared class loader and you try to cast it to a class loaded by the webApp class loader.</p> <p>You can ensure that your web-app dependency is the same than the server provided implementation or just exclude the dependency from the web app when packaging it.</p> <p>If you're using maven just set the scope to <code>provided</code>.</p>