My Service handler throws an NPE. But the service returns a misleading error message:
[andreas@Andreass-Pro training]$ cdap-cli.sh call service Training.PurchaseService GET customers/orange
Successfully connected CDAP instance at http://127.0.0.1:10000
Error: 500: Transaction failure when committing changes. Aborted transaction.
The Service runner should distinguish better what kinds of errors happened.