Data Lista Handler Design Pattern and paging queries

Question

I'm using Toplink in an MVC (Regular Beans, JSP and Struts) application. I'm not using ADF. At least not until i make up my mind on the features-portability tradeoff.
Anyway, my application will have to use queries to show the data to the user. This can easily be accomplished by putting the search parameters on my jsp and using ReadAllQuery to compose my query.
My problem is that the result can return a large amount of records and show all this records at once on the jsp might take a time the user won't be willing to wait. That's when paging the results will come handy.
In another application of mine i use paging manipulating the rownum of the query, but in that case, i had control of the whole sql statement. As this is the first time i'm working with Toplink, i'm feeling that can't be done.
There's the Data List Handler design pattern too, but that one also manipulates the sql statement.
I'm wondering now whether paging can be accomplished using Toplink..? Will i have to use ADF...? This kind of stuff.
Thanks a lot to all.
- Eduardo

Answer 1

Eduardo,
What you need to do is use Cursors in TopLink.Scrollable cursors enable you to scroll through a result set from the database without reading the whole result set in a single database read. The ScrollableCursor class implements the Java ListIterator interface to allow for direct and relative access within the stream. Scrollable cursors also enable you to scroll forward and backward through the stream.
Here is an example:
ReadAllQuery query = new ReadAllQuery();
query.setReferenceClass(Employee.class);
query.useScrollableCursor();
ScrollableCursor cursor = (ScrollableCursor) session.executeQuery(query);
while (cursor.hasNext()) {
System.out.println(cursor.next().toString());
cursor.close();
I hope this answers your question.
Deepak