It seems that newer versions of Keycloak removed the Oracle driver for licensing issues. keycloak/keycloak#29491 The solution would be to externally install the driver (you could use initContainers, ...

I would not suggest using the 3.x driver with neo4j 2.x. Nevertheless could you provide some more information how you retrieve a connection in your code? The ClassNotFoundException should not be ...

Here we explain the difference between the four JDBC driver types, and how to choose the right JDBC driver for your database-driven Java apps.