Ajax + server pagination with datascroller

[lucias]

I have developed (almost copied if i have to be honest ) an ExtendedDataModel that supports Pagination on the server side (by querying a db). Everything works as i expected, the pagination occurs and works fine. But, at the same time, i want to load the data of each page in client side with ajax, so i would also like to set the clientRows property for my extendedDataTable, and not only the rows attribute that divides each logical page. In general, i want to be able to set clientRows < rows, so i get server side pagination + ajax loading in each page. But, at the moment this only works when i set clientRows=rows which obviously isn´t what i need.

What is happening right now is that if i set the clientRows attribute, then the walk method recieves a range which goes only up to clientRows rows, and ignores the row attribute completely. If i dont set clientRows, then the row attribute is passed (ok!) as the range limit (totalRows). I don´t know if this helps.

How can i accomplish this?

I post relevant code below.

The PaginationDataModel is as follows:

public abstract class PaginationDataModel<T> extends ExtendedDataModel<T> {

private SequenceRange cachedRange;
private Integer cachedRowCount;
private List<T> cachedList;
private Object rowKey;

/**
 * 
 * @param firstRow
 * @param numRows
 * @return
 */
public abstract List<T> getDataList(int firstRow, int numRows);
public abstract Object getKey(T t);
public abstract int getTotalCount();

@Override
public void walk(FacesContext ctx, DataVisitor dv, Range range, Object argument) {

   SequenceRange sr = (SequenceRange) range;

   if (cachedList == null || !equalRanges(cachedRange, sr)) {
  cachedList = getDataList(sr.getFirstRow(), sr.getRows());
  cachedRange = sr;
   }

   for (T t : cachedList) {
   if (getKey(t) == null) {
   /*
  * the 2nd param is used to build the client id of the table
  * row, i.e. mytable:234:inputname, so don't let it be null.
  */
   throw new IllegalStateException("found null key");
   }
  dv.process(ctx, getKey(t), argument);
   }

}

/*
* The rowKey is the id from getKey, presumably obtained from
* dv.process(...).
*/
@Override
public void setRowKey(Object rowKey) {
   this.rowKey = rowKey;
}

@Override
public Object getRowKey() {
   return rowKey;
}

@Override
public boolean isRowAvailable() {
   return (getRowData() != null);
}

@Override
public int getRowCount() {
   if (cachedRowCount == null) {
  cachedRowCount = getTotalCount();
   }
   return cachedRowCount;
}

@Override
public T getRowData() {
   for (T t : cachedList) {
   if (getKey(t).equals(this.getRowKey())) {
   return t;
   }
   }
   return null;
}

protected static boolean equalRanges(SequenceRange range1, SequenceRange range2) {
   if (range1 == null || range2 == null) {
   return range1 == null && range2 == null;
   } else {
   return range1.getFirstRow() == range2.getFirstRow() && range1.getRows() == range2.getRows();
   }
}

/*
* get/setRowIndex are used when doing multiple select in an
* extendedDataTable, apparently. Not tested. Actually, the get method is
* used when using iterationStatusVar="it" & #{it.index}.
*/
@Override
public int getRowIndex() {
   if (cachedList != null) {
   ListIterator<T> it = cachedList.listIterator();
   while (it.hasNext()) {
  T t = it.next();
   if (getKey(t).equals(this.getRowKey())) {
   return it.previousIndex() + cachedRange.getFirstRow();
   }
   }
   }
   return -1;
}

@Override
public void setRowIndex(int rowIndex) {
   int upperBound = cachedRange.getFirstRow() + cachedRange.getRows();
   if (rowIndex >= cachedRange.getFirstRow() && rowIndex < upperBound) {
   int index = rowIndex % cachedRange.getRows();
  T t = cachedList.get(index);
  setRowKey(getKey(t));
   }
}

@Override
public Object getWrappedData() {
   throw new UnsupportedOperationException("Not supported yet.");
}

@Override
public void setWrappedData(Object data) {
   throw new UnsupportedOperationException("Not supported yet.");

}

public List<T> getCachedList() {
   return cachedList;
}
}

And the extendedDataTable with dataScroller:

<rich:panel id="idPanel">
<rich:extendedDataTable value="#{someBean.someModel}" id="tableId"
   selectionMode="#{someBean.selectionMode}" selection="#{someBean.selection}" 
rows = "20" clientRows="#{someBean.clientRows}" var="someItem" style="height:300px;">

  <a4j:ajax execute="idPanel" event="selectionchange" listener="# {someBean.selectionListener}" render="@none" />
  columns and more columns...

  <f:facet name="footer"><rich:dataScroller for="tableId" page="#{someBean.currentPage}"  /></f:facet>

</rich:extendedDataTable>
</rich:panel>

Thank you and excuse my english!