String mapKeyClassName = mappedKeyMapAccessor.getMapKeyClass().getName();
// Create the one to one map key mapping.
OneToOneMapping keyMapping = new OneToOneMapping();
keyMapping.setReferenceClassName(mapKeyClassName);
keyMapping.dontUseIndirection();
keyMapping.setDescriptor(getDescriptor().getClassDescriptor());
// Process the map key join columns.
EntityAccessor mapKeyAccessor = getProject().getEntityAccessor(mapKeyClassName);
MetadataDescriptor mapKeyClassDescriptor = mapKeyAccessor.getDescriptor();