The class org.mvel2.util.JITClassLoader references the method sun.misc.Unsafe#defineClass(String, byte, int, int), which has been removed in OpenJDK 8.
The fix seems to be to call the defineClass() method in the base class unconditionally and remove all code referring to sun.misc.Unsafe.
pending MVEL 2.2.0.Final (when it is available for download)
see also http://jira.codehaus.org/browse/MVEL-299
should fixed in mvel-2.1.6-2.fc21
Task info: http://koji.fedoraproject.org/koji/taskinfo?taskID=6830633