The JavaDoc for the JDBC Wrapper class (http://docs.oracle.com/javase/6/docs/api/java/sql/Wrapper.html) says unwrap() should
1) return itself or a proxy when the reicever implements the interface
2) return the wrapped object or a proxy when the wrapped object implements the interface
3) call the wrapped object's unwrap() method if the receiver is a wrapper
4) other throw a SQL exception
JBossWrapper only does 2 and 4.
This means that is you have a WrappedConnectionJDK6 which wraps another wrapper which wraps OracleConnection, there you cannot get to the OracleConnection.