Pagination in Hibernate and EJB3

This class with SQL Server 2000 and jTDS 0.8.1 and it works very well.

Enjoy!


/*
* Created on Oct 27, 2004
*/
package com.ugs.it.salescentre.navigation;

import java.util.List;

import org.apache.log4j.Logger;

import com.ugs.it.salescentre.logger.SalesCentreLogger;

import net.sf.hibernate.HibernateException;
import net.sf.hibernate.Query;
import net.sf.hibernate.ScrollableResults;

/**
* This class provides pagination for displaying results from a large result set
* over a number of pages (i.e. with a given number of results per page).
*
* Taken from http://blog.hibernate.org/cgi-bin/blosxom.cgi/2004/08/14#fn.html.
*
* @author Gavin King
* @author Eric Broyles
*/
public class Page
{

private List results;
private int pageSize;
private int page;
private ScrollableResults scrollableResults;
private int totalResults = 0;

/**
* Construct a new Page. Page numbers are zero-based, so the
* first page is page 0.
*
* @param query
* the Hibernate Query
* @param page
* the page number (zero-based)
* @param pageSize
* the number of results to display on the page
*/
public Page(Query query, int page, int pageSize)
{
this.page = page;
this.pageSize = pageSize;
try
{
scrollableResults = query.scroll();
/*
* We set the max results to one more than the specfied pageSize to
* determine if any more results exist (i.e. if there is a next page
* to display). The result set is trimmed down to just the pageSize
* before being displayed later (in getList()).
*/
results = query.setFirstResult(page * pageSize).setMaxResults(
pageSize + 1).list();
}
catch (HibernateException e)
{
getLogger().error(
"Failed to get paginated results: " + e.getMessage());
}

}

public boolean isFirstPage()
{
return page == 0;
}

public boolean isLastPage()
{
return page >= getLastPageNumber();
}

public boolean hasNextPage()
{
return results.size() > pageSize;
}

public boolean hasPreviousPage()
{
return page > 0;
}

public int getLastPageNumber()
{
/*
* We use the Math.floor() method because page numbers are zero-based
* (i.e. the first page is page 0).
*/
double totalResults = new Integer(getTotalResults()).doubleValue();
return new Double(Math.floor(totalResults / pageSize)).intValue();
}

public List getList()
{
/*
* Since we retrieved one more than the specified pageSize when the
* class was constructed, we now trim it down to the pageSize if a next
* page exists.
*/
return hasNextPage() ? results.subList(0, pageSize) : results;
}

public Logger getLogger()
{
return SalesCentreLogger.getStaticLogger(this);
}

public int getTotalResults()
{
try
{
getScrollableResults().last();
totalResults = getScrollableResults().getRowNumber();
}
catch (HibernateException e)
{
getLogger().error(
"Failed to get last row number from scollable results: "
+ e.getMessage());
}
return totalResults;
}

public int getFirstResultNumber()
{
return page * pageSize + 1;
}

public int getLastResultNumber()
{
int fullPage = getFirstResultNumber() + pageSize - 1;
return getTotalResults() < fullPage ? getTotalResults() : fullPage;
}

public int getNextPageNumber()
{
return page + 1;
}

public int getPreviousPageNumber()
{
return page - 1;
}

protected ScrollableResults getScrollableResults()
{
return scrollableResults;
}

}



Reference