smallrye make foreach conditiont Multi - if-statement

Question

I want to make a category tree,
here is the category structure
class category{
private String id;
private String parentId;
private List<CategoryDto> children;
}
children at the beginning is empty,
parentId if null is a parent otherwise it is children.
I want to return this result:
[
{
"id": "61eb379e6d797574df47cfc3",
"parentId": "",
"children": [
{
"id": "61ea7e5f1323dd3731dd304a",
"parentId": "61eb379e6d797574df47cfc3",
"children": null
},
{
"id": "61ea8f471323dd3731dd304c",
"status": "PUBLISHED",
"parentId": "61eb379e6d797574df47cfc3",
"children": null
}
]
}
]
I did with classic programming I want to migrate to reactive programming with mutiny smallrye here is my code:
#Blocking
public Uni<List<CategoryDto>> getAllCategories(Request doc) {
log.info("REST request to find Categories : {}", doc);
Map<String, Object> parent = new HashMap<>();
List<CategoryDto> all = categoryRepository
.streamAllAggregators(doc).subscribe().asStream().map(it -> aggregatorMapper.categoryToCategoryDto(it, doc.getLang())).collect(toList());
List<CategoryDto> listParent = categoryRepository
.findByParentId("").subscribe().asStream().map(it -> aggregatorMapper.categoryToCategoryDto(it, doc.getLang())).collect(toList());
List<CategoryDto> listChildren = all.stream()
.filter(n -> n.getParentId() != null)
.collect(Collectors.toList());
List<CategoryDto> categoryDtoList = new ArrayList<>();
for (int i = 0; i < listParent.size(); i++) {
categoryDtoList = new ArrayList<>();
for (int j = 0; j < listChildren.size(); j++) {
if (listChildren.get(j).getParentId().equals(listParent.get(i).getId().toString())) {
categoryDtoList.add(listChildren.get(j));
}
}
listParent.get(i).setChildren(categoryDtoList);
}
return Uni.createFrom().item(listParent);
}

Answer 1

Taking my reply from https://github.com/smallrye/smallrye-mutiny/issues/823:
Something like this will work:
public Uni<List<CategoryDto>> getAllCategories(Request doc) {
Map<String, Object> parent = new HashMap<>();
Multi<CategoryDto> all = categoryRepository.streamAllAggregators(doc).map(s -> aggregatorMapper.categoryToCategoryDto(s, doc.getLang()));
Uni<List<CategoryDto>> listParent = categoryRepository
.findByParentId("").map(it -> aggregatorMapper.categoryToCategoryDto(it, doc.getLang())).collect().asList();
Uni<List<CategoryDto>> listChildren = all.select().where(n -> n.getParentId() != null).collect().asList();
return Uni.combine().all().unis(listParent, listChildren).combinedWith((parents, children) -> {
// Or whatever you need to do.
List<CategoryDto> categoryDtoList;
for (int i = 0; i < parents.size(); i++) {
categoryDtoList = new ArrayList<>();
for (int j = 0; j < children.size(); j++) {
if (children.get(j).getParentId().equals(parents.get(i).getId().toString())) {
categoryDtoList.add(children.get(j));
}
}
parents.get(i).setChildren(categoryDtoList);
}
return parents;
});
}