Kettle / Pentaho Data Integration - unable to create a Database Connection (XulException: java.lang.reflect.InvocationTargetException)

Question

Having finally got kettle to start and not hang, I still cannot use it to much avail, as when I try to create a new Database Connection (after creating a new Transformation) I get this error:

org.pentaho.ui.xul.XulException: java.lang.reflect.InvocationTargetException

Thereafter, I get this more general error for the same actions:

General error in dialog

In order to get the first 'java...TargetException' again, I have to close and restart kettle.
Note, this also happens when I load an existing kettle job and try to edit its database connection.

Could this be a configuration issue? A missing or misplaced file ? What is the Target that is failing to be Invoked? Thanks in advance for your help.

My config:

macos 10.12.6 (Sierra)
Pentaho Data Integration (or kettle) 7.1.0
java version "9.0.4"

Answer 1

As I found out from the Pentaho Data Integration forum, it was a matter of my version of Java.
I uninstalled Java 9 and installed Java 8 and then no longer got this error.

Answer 2

There is a .kettle directory in your home directory. In this directory, you may have a db-cache-<some.numbers> file. If that is the case: stop spoon, delete the db-cache file, and restart spoon.

If it doesn't work, an other file in that directory may be corrupted.