    001    // Copyright 2007, 2008, 2010 The Apache Software Foundation
    002    //
    003    // Licensed under the Apache License, Version 2.0 (the "License");
    004    // you may not use this file except in compliance with the License.
    005    // You may obtain a copy of the License at
    006    //
    007    // http://www.apache.org/licenses/LICENSE-2.0
    008    //
    009    // Unless required by applicable law or agreed to in writing, software
    010    // distributed under the License is distributed on an "AS IS" BASIS,
    011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    012    // See the License for the specific language governing permissions and
    013    // limitations under the License.
    014
    015    package org.apache.tapestry5.internal.grid;
    016
    017    import java.util.Collection;
    018    import java.util.Collections;
    019    import java.util.Comparator;
    020    import java.util.List;
    021
    022    import org.apache.tapestry5.PropertyConduit;
    023    import org.apache.tapestry5.grid.ColumnSort;
    024    import org.apache.tapestry5.grid.GridDataSource;
    025    import org.apache.tapestry5.grid.SortConstraint;
    026    import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
    027
    028    @SuppressWarnings("all")
    029    public class CollectionGridDataSource implements GridDataSource
    030    {
    031        private final List list;
    032
    033        public CollectionGridDataSource(final Collection collection)
    034        {
    035            assert collection != null;
    036            list = CollectionFactory.newList(collection);
    037        }
    038
    039        public int getAvailableRows()
    040        {
    041            return list.size();
    042        }
    043
    044        public void prepare(int startIndex, int endIndex, List<SortConstraint> sortConstraints)
    045        {
    046            for (SortConstraint constraint : sortConstraints)
    047            {
    048                final ColumnSort sort = constraint.getColumnSort();
    049
    050                if (sort == ColumnSort.UNSORTED)
    051                    continue;
    052
    053                final PropertyConduit conduit = constraint.getPropertyModel().getConduit();
    054
    055                final Comparator valueComparator = new Comparator<Comparable>()
    056                {
    057                    public int compare(Comparable o1, Comparable o2)
    058                    {
    059                        // Simplify comparison, and handle case where both are nulls.
    060
    061                        if (o1 == o2)
    062                            return 0;
    063
    064                        if (o2 == null)
    065                            return 1;
    066
    067                        if (o1 == null)
    068                            return -1;
    069
    070                        return o1.compareTo(o2);
    071                    }
    072                };
    073
    074                final Comparator rowComparator = new Comparator()
    075                {
    076                    public int compare(Object row1, Object row2)
    077                    {
    078                        Comparable value1 = (Comparable) conduit.get(row1);
    079                        Comparable value2 = (Comparable) conduit.get(row2);
    080
    081                        return valueComparator.compare(value1, value2);
    082                    }
    083                };
    084
    085                final Comparator reverseComparator = new Comparator()
    086                {
    087                    public int compare(Object o1, Object o2)
    088                    {
    089                        int modifier = sort == ColumnSort.ASCENDING ? 1 : -1;
    090
    091                        return modifier * rowComparator.compare(o1, o2);
    092                    }
    093                };
    094
    095                // We can freely sort this list because its just a copy.
    096
    097                Collections.sort(list, reverseComparator);
    098            }
    099        }
    100
    101        /**
    102         * Returns the type of the first element in the list, or null if the list is empty.
    103         */
    104        public Class getRowType()
    105        {
    106            return list.isEmpty() ? null : list.get(0).getClass();
    107        }
    108
    109        public Object getRowValue(int index)
    110        {
    111            return list.get(index);
    112        }
    113
    114    }