Weblogic - The user must supply a JDBC connection ?

Yes, you must put that configuration on your config.xml:

<jdbc-system-resource>
  <name>TestXADS</name>
  <target>AdminServer</target>
  <descriptor-file-name>jdbc/TestXADS-jdbc.xml</descriptor-file-name>
</jdbc-system-resource>

 But, You must restart the server after that.

And another detail:

If you are using oracle, I d'ont know why but you cannot use this:
name="hibernate.hbm2ddl.auto" value="create-drop" />

You only get use with this:
 name="hibernate.hbm2ddl.auto" value="update" />

My opinion? Weblogic is a shut. JBoss as releases are the best.