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From CatalinPetrisor <mariuscata...@yahoo.com>
Subject Re: SortableModel and t:dataTable changes/improvements
Date Tue, 27 Nov 2007 09:31:45 GMT

That's a very good idea. However, in the latest svn sources the HtmlDataTable
component still uses SortableModel class to set the current sort column.
Wouldn't be normal to use BaseSortableModel class to allow extensibility?

Thanks.


Mike Kienenberger wrote:
> 
> As a first step in this process, I've separated SortableDataModel into
> SortableDataModel (current behavior, final, subclass of
> BaseSortableDataModel) and BaseSortableDataModel (extendable, works on
> Comparators).
> 
> I tested all of the simple examples involving dataTable at one point,
> but it's possible that something may have slipped by me that I didn't
> notice.
> 
> 
> On 3/14/07, Mike Kienenberger <mkienenb@gmail.com> wrote:
>> 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>
>>
> 
> 

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