When running Solr in java9, and using the morphlines contrib(s) users may encounter vague errors such as...
This error comes directly from the morphlines code, and relates to the use of wildcards in the importCommands declaration of of morphlines *.conf files used – for example...
Using wildcards like * and ** in morphline's importCommands config options do not work in java9 due to changes in the underlying JVM classloader.
This issue is tracked up stream in: https://github.com/kite-sdk/kite/issues/469
The workaround is to only use fully qualified command class names in importCommands declaration, one for each distinct command used in that conf file.