How to use datastore cursors with jpa on GAE

Any body know how to use Datastore Cursors with JP开发者_C百科A?

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Can you try this (adapted from the JDO sample):

List<Employee> results = (List<Employee>) query.execute();
// Use the first 20 results...

Cursor cursor = JPACursorHelper.getCursor(results);
String cursorString = cursor.toWebSafeString();
// Store the cursorString...

// ...

// Query query = the same query that produced the cursor
// String cursorString = the string from storage
Cursor cursor = Cursor.fromWebSafeString(cursorString);
query.setHint(JPACursorHelper.CURSOR_HINT, cursor);
query.setFirstResult(0);
query.setMaxResults(20);

List<Employee> results = (List<Employee>) query.execute();
// Use the next 20 results...