In issue #976 JDK11 build was taken to use but one problem related to Naked Objects pattern remains. Issue description from @lbroman:

In my PR #980 I have left language source and target at 8 for the naked-objects/dom module. This is because java 11 bytecode breaks the datanucleus enhancer, even if they claim that 5.2 should support java 11 bytecode.
I have tried fiddling with the datanucleus dependency versions because the module uses datanucleus core 5 and apis from 4 so I thought that might be the problem. However, bumping up the versions breaks other stuff as they seem to have moved around some classes between 4 and 5.