JNI – Java Native Interface – is an interface for cooperating Java and legacy code. Oracle RDBMS doesn’t support it officially in embedded Oracle JVM (aka “Aurora”):
Oracle Database does not support the use of JNI in Java applications. If you use JNI, then your application is not 100 percent pure Java and the native methods require porting between platforms. Native methods can cause server failure, violate security, and corrupt data.
All true – and nevertheless it’s working.
Timur Akhmadeev's blog 