Did you already try the following code:
DataSource ds = (DataSource) ConnectorRuntime.getRuntime().lookupNonTxResource("jdbc/jooss_dev", false);
This code worked pretty fine for me and this is the same way used in JDBCRealm to get a DataSource. But remember that you can't call lookupNonTxResource() during realm initialization or you will get the same error. Just call this method when you'r going to use the DataSource.
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