When users follow the tutorial with curl commands, they might not follow the steps from code to token. It might cause the token service to throw an NPE as the authorization code doesn't exist. In a programming world, this won't happen as the authorization code and token retrieval should be at the same time.
We need to update the handler to output an easy-to-understand error code.
Please double-check the kafka-oauth as well for the same issue.
stevehu
commented
3 years ago 
When users follow the tutorial with curl commands, they might not follow the steps from code to token. It might cause the token service to throw an NPE as the authorization code doesn't exist. In a programming world, this won't happen as the authorization code and token retrieval should be at the same time.
We need to update the handler to output an easy-to-understand error code.
Please double-check the kafka-oauth as well for the same issue.