Scrolling Resultset example?

Question

this is a posting from another thread that I was looking for clarification on. I understand what's being said but I don't quite understand how to reference the resultSet from this explanation:
USE a Scrollable ResultSet object and put it in the session. Keep a variable that identifies where in the resultset ur pointer is at any point of time.
Scrollable ResultSets are a feature only available with JDBC 2.0 onwards... so make sure u have THAT first.
Create a Statement like this...
Statement st =
con.createStatement(ResultSet.SCROLLABLE);
Then run the query n store it in the resultset
ResultSet rs = st.executeQuery(sql);
Then move ur pointer to any record u want with methods present in the ResultSet interface:
relative(int rows) that takes you 'rows' rows ahead.
absolute(int row) that takes your pointer to the 'row'th ROW.
Make sure u use 'refreshRow()' so u have the latest content at any point of time. This refreshes the contents in that row. there is also something called refresh() BUT THAT would minimise performace.
Store this resultset object in the session and call it in each page u want starting with the record number u want to. !!
Hope this helps... aXe!
My question is, does someone have a simple example page that does what is described above? Also, to get the number of pages that will be involved, would you first "SELECT * FROM table" and count the rows, divide by the number of rows to display per page, and then create a URL for each number to jump to the next grouping of rows doing something like this?:
(suppose you want 10 rows per page)
2
4
the code would simple do:
<% String page = request.getParameter("page");
rs.absolute(page);
while (rs.next()){ %>
<% ...print out row contents here... %>
<%}%>
Does this sound correct...where does the "refreshRow()" need to go to clear the row? Also, would you need to use LIMIT (to 10 rows)in the SELECT statement?
Any help in understanding this is greatly appreciated!
Chuk.

Answer 1

well, with some tweaking I had figured it out but ran into another problem:
I need to know in advance how many pages will be required to display the entire ResultsSet to print 1,2,3,4, etc as hyperlinks and link them to the jsp to scroll back and forth. So I tried to do the following
(suppose the ResultSet hold 12 records total which I would get like this):
//get total number of rows, this is a very round about way but I'm new to this
int totalRows = 0;
rs.last();
totalRows = rs.getRow();
rs.first();
rs.previous();
//set the number of rows to display per page
int pageRows = 10;
//initialize variable to hold the number of pages needed
int pages = 0;
//So then I would calculate the number of pages:
pages = totalRows/pageRows;
//then print the page numbers
for (int i = 0; i <= pages){
out.println("<a href sample.jsp?page="+i+"> "+i);
This would work great if only the integer was always rounded up. In this example, I want 10 rows per page displayed and there are 12 total. In this calculation I would want the variable "pages" to equal 2 b/c you would have one page of 10 rows and then the second page of 2 rows. The type integer is always rounded down it seems so I end of with a value of "1" in the integer "pages"
There must be a better way to do this...anyone have any ideas or have you done this before?
thanks in advance,
Chuck