No session repository could be auto-configured, check your configuration (session store type is 'null')
You have Spring Session on your classpath and no store was provided. We can't take that decision for you as if your classpath changes, the store type may change according to our preferences and you'd lose them without any sort of warning.
Historically we only supported redis so if you have that we'll use it transparently. Please set spring.session.store-type to the store you want to use for Spring Session. If Spring Session is on your classpath and you don't want to use it right now, set spring.session.store-type=none
Update: given the number of upvotes, this looks like a confusing error message so I've opened #9284 to improve it.