I used a bad package naming for this software that needed improvements. Version 1.3.0 of the #Java bindings for #libayatana-appindicator and #libappindicator fixes this.
https://github.com/purejava/appindicator-gtk3-java/releases/tag/1.3.0
#kdewallet suffered from the same problem that already led to 'split jar' problems in another software. This is fixed with #release 1.3.0.
Well, partially fixed.
I learned today, that there is an exception to the rule, that the #package name of the #Java #interface needs to follow the interface name of the #D-Bus interface.
There is an @DBusInterfaceName #annotation available, that lets you put your Java interface in any package you like and so adhere to the Java 9 Platform Module System (#JPMS) as well, without causing 'split jar' problems.
Definitely fixed with #release 1.3.1.