chore: java data helper group sorting (#4791)

Author: yanmariomenev

examples-standalone/kendoangular-java-integration/backend/src/main/java/telerik/demo/datasource/QueryableExtensions.java

@@ -48,9 +48,34 @@ public static <T> DataSourceResult toDataSourceResult(List<T> data, DataSourceRe
  // Get total count after filtering (before paging)
  long total = filteredData.size();
 
- // Apply sorting
+ // Apply sorting - need to combine group sorting with regular sorting
+ List<SortDescriptor> sortDescriptors = new ArrayList<>();
+ 
+ // First, add sorts from group descriptors (groups take precedence)
+ if (request.getGroup() != null && !request.getGroup().isEmpty()) {
+ for (GroupDescriptor group : request.getGroup()) {
+ SortDescriptor sort = new SortDescriptor();
+ sort.setField(group.getField());
+ // Use group's dir if specified, otherwise default to ascending
+ sort.setDir(group.getDir() != null && !group.getDir().isEmpty() ? group.getDir() : "asc");
+ sortDescriptors.add(sort);
+ }
+ }
+ 
+ // Then add regular sort descriptors (if they don't conflict with group sorting)
  if (request.getSort() != null && !request.getSort().isEmpty()) {
- filteredData = applySort(filteredData, request.getSort());
+ for (SortDescriptor sort : request.getSort()) {
+ boolean alreadySorted = sortDescriptors.stream()
+ .anyMatch(s -> s.getField().equals(sort.getField()));
+ if (!alreadySorted) {
+ sortDescriptors.add(sort);
+ }
+ }
+ }
+ 
+ // Apply the combined sorting
+ if (!sortDescriptors.isEmpty()) {
+ filteredData = applySort(filteredData, sortDescriptors);
  }
 
  // Apply grouping (grouping should NOT be affected by paging unless groupPaging is enabled)
@@ -471,14 +496,16 @@ private static <T> List<GroupResult> applyGrouping(List<T> data, List<GroupDescr
  }
 
  GroupDescriptor currentGroup = groupDescriptors.get(level);
+ 
+ // Use LinkedHashMap to preserve insertion order (data is already sorted)
  Map<Object, List<T>> grouped = data.stream()
  .collect(Collectors.groupingBy(item -> {
  try {
  return getFieldValue(item, currentGroup.getField());
  } catch (Exception e) {
  return null;
  }
- }));
+ }, LinkedHashMap::new, Collectors.toList()));
 
  List<GroupResult> results = new ArrayList<>();
  boolean hasMoreGroups = level + 1 < groupDescriptors.size();
@@ -489,22 +516,21 @@ private static <T> List<GroupResult> applyGrouping(List<T> data, List<GroupDescr
  groupResult.setValue(entry.getKey());
 
  if (hasMoreGroups) {
- // Recursively group
+ // Recursively group nested levels
  List<GroupResult> subGroups = applyGrouping(entry.getValue(), groupDescriptors, level + 1);
  groupResult.setItems(subGroups);
  groupResult.setHasSubgroups(true);
- // Count total items in all subgroups
  int totalItems = subGroups.stream()
  .mapToInt(g -> g.getItemCount() != null ? g.getItemCount() : 0)
  .sum();
  groupResult.setItemCount(totalItems);
  } else {
+ // Leaf level - store the actual items
  groupResult.setItems(entry.getValue());
  groupResult.setHasSubgroups(false);
  groupResult.setItemCount(entry.getValue().size());
  }
 
- // Calculate aggregates for this group
  if (currentGroup.getAggregates() != null && !currentGroup.getAggregates().isEmpty()) {
  List<AggregateDescriptor> aggregateDescriptors = currentGroup.getAggregates().stream()
  .map(af -> {