JSON binding was added to EclipseLink in version 2.4. If you are using a version of that does not contain this version (i.e. WebLogic 10.3.4 (11g) contains EclipseLink 2.1.2), then by default you won't have access to this functionality. The recommended solution to this problem is to create a shared library in WebLogic for the newer release of EclipseLink.
