This was an issue in EclipseLink 2.3.2 that is included with WebLogic 12.1.1. This issue has since been fixed. Here is a link to an article I wrote that demonstrates how to point to a newer version of EclipseLink using a shared library in WebLogic:
The other strange thing is that I have a custom adapter and it isn't called.
Can you provide more details about your adapter?