Pagination in Google App Engine with Java

Question

I need to create simple pagination of objects, but when I read manual I found out that query.setRange(5, 10); will fetch 10 objects, even when only 5 objects are needed.

Answer 1

How about this:

List results = (List) 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.setRange(0, 20);

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

From:

How to use datastore cursors with jpa on GAE

Also:

http://groups.google.com/group/google-appengine-java/browse_thread/thread/5223215ff24c3b3e/d22297d1d76a9c8b

Or without JPA see:

http://code.google.com/appengine/docs/java/javadoc/com/google/appengine/api/datastore/Cursor.html