Well, it will give you the database connection from the original driver. Use it as little as possible, since it won't give you the error checking and management features of the wrapped connection. Other than this, I don't know what to say about it. If you need more info, look at the source code.
David, I already looked into the source code and found something that could help, e.g.:
There is an import for org.jboss.resource.adapter.jdbc.WrappedConnection, which is used later for getUnderlyingConnection.
But WrappedConnection, is not contained in any of the jar
files which are contained in jboss (3.0.7).
jboss-jca.jar contains org.jboss.resource.adapter./... but no classes below.
I assume with the example source mentioned above I could solve my problem if I would have the corresponding jar files.
Just for the case that others have the same problem: In the meantime I found out that I have to compile the sources, then an additional jar file is created which contains the necessary class(es). Now I have an exception in LocalConnection, but I'll guess I can find out why.