So, have a customized binding built under the most recent OpenHab development environment (using Eclipse IDE), following the official/new guidelines for creating a binding, and the binding has worked successfully and stable under OpenHab 2.4.0 release (Openhabian running on Raspberry Pi 3b+).
However, due to requirements for upgrading OpenHab due to other needed bindings, I updated OpenHab to version 2.5.0M3. Following the upgrade, my customized binding stopped working, and the log states:
2019-10-14 20:18:35.759 [ERROR] [core.thing.internal.ThingManagerImpl] - Exception occurred while initializing handler of thing 'freeathome:bridge:47065664': rocks.xmpp.core.session.Module: Provider rocks.xmpp.websocket.net.client.WebSocketModule not a subtype java.util.ServiceConfigurationError: rocks.xmpp.core.session.Module: Provider rocks.xmpp.websocket.net.client.WebSocketModule not a subtype at java.util.ServiceLoader.fail(ServiceLoader.java:239) ~[?:?] at java.util.ServiceLoader.access$300(ServiceLoader.java:185) ~[?:?] .. ..
Have no clue why the error occurs. The customized binding still use a /lib folder due to requirements for a customized Websocket/XMPP package which is not available otherwise, i.e. the package which the error points at.
The error then relates to the bridge of a smarthome setup, where a customized Websocket/XMPP stream is required to achieve a successful connection, and the binding utilizes the rocks.xmpp library as base for the customized code.