Servoy developer until version 8.2 is build on Eclipse 4.5.0 (mars) or lower, that version of eclipse doesn't work with Java9.

Servoy 8.3 will upgrade to Eclipse 4.7 (Oxygen) that eclipse does support Java9 but it could be that the servoy.ini file does need to contain this vm-arg:

--add-modules=java.se.ee

See http://openjdk.java.net/jeps/261 for more information about those new Java 9 Module system properties