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/*
* Copyright 2000-2022 Vaadin Ltd.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.vaadin.data.provider;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import java.util.Set;
import java.util.stream.Collectors;
import java.util.stream.Stream;
/**
* Abstract base class for implementing
* {@link BackEndHierarchicalDataProvider}s.
*
* @author Vaadin Ltd
* @since 8.1
*
* @param <T>
* data type
* @param <F>
* filter type
*/
public abstract class AbstractBackEndHierarchicalDataProvider<T, F>
extends AbstractHierarchicalDataProvider<T, F>
implements BackEndHierarchicalDataProvider<T, F> {
private List<QuerySortOrder> sortOrders = new ArrayList<>();
private HierarchicalQuery<T, F> mixInSortOrders(
HierarchicalQuery<T, F> query) {
if (sortOrders.isEmpty()) {
return query;
}
Set<String> sortedPropertyNames = query.getSortOrders().stream()
.map(SortOrder::getSorted).collect(Collectors.toSet());
List<QuerySortOrder> combinedSortOrders = Stream
.concat(query.getSortOrders().stream(),
sortOrders.stream()
.filter(order -> !sortedPropertyNames
.contains(order.getSorted())))
.collect(Collectors.toList());
return new HierarchicalQuery<>(query.getOffset(), query.getLimit(),
combinedSortOrders, query.getInMemorySorting(),
query.getFilter().orElse(null), query.getParent());
}
@Override
public Stream<T> fetchChildren(HierarchicalQuery<T, F> query) {
return fetchChildrenFromBackEnd(mixInSortOrders(query));
}
@Override
public boolean isInMemory() {
return false;
}
@Override
public void setSortOrders(List<QuerySortOrder> sortOrders) {
this.sortOrders = Objects.requireNonNull(sortOrders,
"Sort orders cannot be null");
refreshAll();
}
/**
* Fetches data from the back end using the given query.
*
* @see HierarchicalQuery
*
* @param query
* the query that defines sorting, filtering, paging and the
* parent item to fetch children from
* @return a stream of items matching the query
*/
protected abstract Stream<T> fetchChildrenFromBackEnd(
HierarchicalQuery<T, F> query);
}
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