WebLogic uses a dummy version of the JFR APIs that is compiled against JDK 8. This is to simplify their use of both the JDK 8 and JDK 9 APIs.

Much of the work to compile against JDK 8 was done in JDK-8152148, but it turns out that the dummy jar doesn't handle Unsafe being moved to jdk.internal.misc, leading to an unexpected NoClassDefFoundError.

I have a fix ready that allows the API to be queried for JFR capability (FlightRecorder.isAvailable) without throwing an exception.