appengine jdo + gwt(requestFactory) 오류

• 오류메시지

Primary key for type Account is of unexpected type java.lang.String
(must be String, Long, or com.google.appengine.api.datastore.Key) 

• 해결책

Try to add this line to your id:
        @Extension(vendorName="datanucleus", key="gae.encoded-pk",
value="true")