Hello Kristof,
I did some more research and maybe found something interesting information concerning the
SimpleNativeJdbcExtractor you use as nativeJdbcExtractor.
In the javadocs of the SimpleNativeJdbcExtractor it says:
This extractor should work with any pool that does not wrap DatabaseMetaData, and will also work with any plain JDBC driver. Note that a pool can still wrap Statements, PreparedStatements, etc: The only requirement of this extractor is that java.sql.DatabaseMetaData does not get wrapped, returning the native Connection of the JDBC driver on metaData.getConnection().
The 'interesting information' here is the fact that it states that if you want to use this class the java.sql.DatabaseMetaData does not get wrapped and returns the native Connection of the JDBC driver on metaData.getConnection().
In your case it apparently doesn't because it is returning null after invoking the getMetaData().getConnection() in the method doGetNativeConnection of the class SimpleNativeJdbcExtractor. If you look into this method you'll see the DEBUG statement 'Returning native Connection [null] for given ....' being called there.
Why the WebLogicNativeJdbcExtractor failes, I do not know (I have never worked with Weblogic). But my guess (and I am just guessing here...) is that it is on the same point (also the method doGetNativeConnection of the class WebLogicNativeJdbcExtractor. What I find strange in the exception trace is that the figure 813 is in the name of the connection implementation class of Weblogic.
Maybe this is refering to an older Oracle version 8.1.3? Maybe there is an older oracle driver jar/zip or something like that in the classpath or libpath, or maybe the jdbc/native drivers of weblogic need to be upgraded?
Good luck!