package flex.messaging.services.remoting;
import java.sql.SQLException;
import java.util.Map;
import javax.sql.RowSet;
import flex.messaging.FlexContext;
import flex.messaging.FlexSession;
import flex.messaging.io.PageableRowSet;
import flex.messaging.io.PagedRowSet;
/**
* A special RemotingService destination that caches a PageableRowSet
* in the current FlexSession to provide legacy paging functionality for
* the deprecated client RecordSet API.
*
* To create a PageableRowSet, a javax.sql.RowSet must be provided instead
* of a java.sql.ResultSet because the data has to be disconnected and
* cacheable.
*
* The RemotingService's JavaAdapter is expected to manage this instance.
*
* @see flex.messaging.io.PageableRowSet
* @author Peter Farland
*/
public class PageableRowSetCache
{
private static final int DEFAULT_PAGE_SIZE = 25;
/**
* A default constructor is required for a RemotingService source.
*/
public PageableRowSetCache()
{
}
/**
* Converts a RowSet into a PageableRowSet, stores the PageableRowSet
* result in the cache and then returns the PageableRowSet. A unique
* id will be created for the PagedRowSet.
*
* @param rowset RowSet to be cached for paged access.
* @param pageSize Size of the first page to be sent to the client. Default
* is 25 if pageSize is set to 0 or less. If all records should be sent at once
* consider not caching the RowSet or specify Integer.MAX_VALUE.
*/
public static PageableRowSet cacheRowSet(RowSet rowset, int pageSize)
{
if (pageSize <= 0)
pageSize = DEFAULT_PAGE_SIZE;
PageableRowSet prs = new PagedRowSet(rowset, pageSize, true);
cachePageableRowSet(prs);
return prs;
}
/**
* Stores the PageableRowSet result in the session to act as a cache
* for the legacy client RecordSet paging feature.
*
* @param rowset PageableRowSet to be cached for paged access.
*/
public static void cachePageableRowSet(PageableRowSet rowset)
{
if (rowset != null)
{
FlexSession session = FlexContext.getFlexSession();
session.setAttribute(rowset.getID(), rowset);
}
}
/**
* Get a subset of records that are cached for the given PageableRowSet id.
*
* @param id The PageableRowSet's id, used to locate it in the current session.
* @param startIndex The absolute position for the record set cursor.
* @param count The size of the page of results to return.
* @return Map The resulting sub-set of data or 'page' requested.
* @see PageableResultSet#getRecords(int, int)
*/
public Map getRecords(String id, int startIndex, int count) throws SQLException
{
Map page = null;
FlexSession session = FlexContext.getFlexSession();
if (session != null)
{
Object o = session.getAttribute(id);
if (o != null && o instanceof PageableRowSet)
{
PageableRowSet rs = (PageableRowSet) o;
page = rs.getRecords(startIndex, count);
}
}
return page;
}
/**
* Remove a PageableRowSet from the current session.
*
* @param id The id of the PageableRowSet to remove from the current session.
*/
public void release(String id)
{
FlexSession session = FlexContext.getFlexSession();
if (session != null)
{
session.removeAttribute(id);
}
}
}