While using JDO or another datastore helper library, applications may encounter a value of ExQ when requesting a query cursor. This value means that there are no more results (entities) to display for that query, and consequently that there are no more query pages to return.
All applications using query cursors should check for an invalid or end of query results marker, and handle this in an application-specific way. A query cursor string that is null or empty (zero length) generally denotes the end of query results. The cursor value ExQ can be handled in the same way.
A word of warning: some third-party datastore helper libraries spawn an exception or error condition when applications attempt to access invalid cursors, or attempt to request a cursor when end of results has already been reached. When using these libraries, it’s important to fully read the documentation and understand how these libraries interact with the App Engine datastore.