I'm was running into a problem trying to get a minion to detect, and poll, a postgresql database. Specifically, I was seeing the following in the logs:

My detector is setup like so:

Additionally, I found the following in `karaf.log`:

However, I found that by adding an Import-Package: org.postgresql;resolution:=optional section to the MANIFEST.MF of the opennms-detector-jdbc jar, I was able to get it working. 

P.s. Thanks to Jesse (from chat) for pointing out that postgresql wasn't being made available for import by the above class.