[jira] Commented: (TOMAHAWK-952) Provide cleaner, consistent sorting for dataTable and selectItems

["Mike Kienenberger (JIRA)" <de...@myfaces.apache.org>]

    [ https://issues.apache.org/jira/browse/TOMAHAWK-952?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12485543 ] 

Mike Kienenberger commented on TOMAHAWK-952:
--------------------------------------------

As a first step in this process, I've separated SortableDataModel into SortableDataModel (current behavior, final, subclass of BaseSortableDataModel) and BaseSortableDataModel (extendable, works with Comparators).

> Provide cleaner, consistent sorting for dataTable and selectItems
> -----------------------------------------------------------------
>
>                 Key: TOMAHAWK-952
>                 URL: https://issues.apache.org/jira/browse/TOMAHAWK-952
>             Project: MyFaces Tomahawk
>          Issue Type: New Feature
>          Components: Extended Datatable, Extended SelectItems, New Component
>    Affects Versions: 1.1.6-SNAPSHOT
>            Reporter: Mike Kienenberger
>         Assigned To: Mike Kienenberger
>            Priority: Minor
>
> My requirements in most cases are to 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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