When not using a <driver ...> specification (explicit driver entries are required only when deploying drivers as modules which is a more complex scenario that is not usually necessary), it is mandatory to set the xa-datasource-class at the pool level for each <xa-datasource ...>.

When not using a <driver ...> specification, for non-XA <datasource ...> pools, it is sometimes necessary (not always required since a default driver class is specified in JDBC 4 compliant implementations but this may need to be overridden in some cases) to explicitly set a <driver-class> or <datasource-class> at the pool level.

No environment variables exist to support configuring the connection class at the pool level so all XA pools and some non-XA pools require custom configuration via scripts that should not be necessary in the most common cases.