I took a look at SortableModel and t:dataTable sorting again last
night. My requirements in most cases are to simply specify a sort
order in the page code, not to allow end-users to manipulate the sort
order. From what I can tell, there's no easy way to do this. I
documented the most effective method I could find on the wiki under a
"static sorting" subheading, but even that method leaves unnecessary
links in the column headers.
At the same time, I looked into what it would take to make sorting
cleaner and more user-friendly.
I came up with a subclass of extended dataTable and a replacement
SortableModel that did what I wanted for the most part:
<my:sortableDataTable
preserveDataModel="true"
value="#{bean.carList}"
var="car"
>
<f:facet name="comparator">
<my:propertyComparator
property="style.color"
descending="true" />
</f:facet>
</my:sortableDataTable>
This is based in part on reusing my components for sorting selectItem
lists. For some reason, couldn't make this work without using
preserveDataModel. [Strangely enough, doing the same thing with the
current t:dataTable sort attributes didn't require preserveDataModel.]
In any case, a comparator component can be any UIComponent that
implements a ComparatorSource interface (ie, public Comparator
getComparator()), which provides a great deal of flexibility.
The propertyComparator implementation basically does the same thing as
the internal guts of the current SortableModel, but is pluggable. I
used beanutils in my comparator rather than EL to process the property
expression, which also eliminates the "rowObjectGet" hack. An "EL
comparator" could be implemented if the EL processing features were
needed.
I think it would be worthwhile to replace the current SortableModel
with a more generic pluggable one. A good start would be to pull all
of the property-resolving/comparison out of it, and stick it into a
comparator like I did. setSortCriteria(List criteria) appears to be
misnomer since only the first item in the list is used -- using a
comparator would also solve that issue as you can create
MultipleComparator that takes a list of other comparators and goes
through them in order.
Following is what DataTable looks like to make this work. Note that
this doesn't handle the current sorting options.
protected DataModel createDataModel()
{
DataModel dataModel = super.createDataModel();
UIComponent comparatorUIComponent = getComparator();
Comparator comparator = null;
if (null != comparatorUIComponent)
{
if (comparatorUIComponent instanceof ComparatorSource)
{
comparator =
((ComparatorSource)comparatorUIComponent).getComparator();
}
else
{
// TODO: need log error instead
throw new RuntimeException("comparatorUIComponent should
implement ComparatorSource");
}
}
boolean isSortable = null != comparator;
if (isSortable)
{
if (!(dataModel instanceof BaseSortableModel))
{
dataModel = new BaseSortableModel(dataModel);
}
((BaseSortableModel)dataModel).setComparator(comparator);
}
return dataModel;
}
After stripping out the comparator stuff from SortableModel, these are
the major changes:
public void setComparator(Comparator _comparator) {
this._comparator = _comparator;
_sort();
}
private void _sort()
{
if (null == _comparator)
{
// restore unsorted order:
_baseIndicesList = _sortedIndicesList = null;
return;
}
//TODO: support -1 for rowCount:
int sz = getRowCount();
if ((_baseIndicesList == null) || (_baseIndicesList.size() != sz))
{
// we do not want to mutate the original data.
// however, instead of copying the data and sorting the copy,
// we will create a list of indices into the original data, and
// sort the indices. This way, when certain rows are made current
// in this Collection, we can make them current in the underlying
// DataModel as well.
_baseIndicesList = new IntList(sz);
}
final int rowIndex = _model.getRowIndex();
_model.setRowIndex(0);
// Make sure the model has that row 0! (It could be empty.)
if (_model.isRowAvailable())
{
Collections.sort(_baseIndicesList, new
RowDataComparator(_comparator, _model));
_sortedIndicesList = null;
}
_model.setRowIndex(rowIndex);
}
protected class RowDataComparator implements Comparator
{
private Comparator dataComparator = null;
private DataModel dataModel = null;
public RowDataComparator(Comparator comparator, DataModel model)
{
this.dataComparator = comparator;
this.dataModel = model;
}
public int compare(Object arg1, Object arg2) {
Integer r1 = (Integer)arg1;
Integer r2 = (Integer)arg2;
dataModel.setRowIndex(r1.intValue());
Object rowData1 = _model.getRowData();
dataModel.setRowIndex(r2.intValue());
Object rowData2 = _model.getRowData();
return dataComparator.compare(rowData1, rowData2);
}
}
Also, here's how I'd like to improve t:selectItems. I've had a custom
subclass of f:selectItems of this working for awhile. Notice how we
can reuse the same propertyComparator component. This particular
implementation can take a list of comparator children and implicitly
wraps them in a MultipleComparator. That's not really possible with
a dataTable facet, so we'd want to provide a MultipleComparator
component.
<my:orderedSelectItems value="#{bean.carList}">
<my:propertyComparator
property="style.color"
descending="false" />
</my:orderedSelectItems>
