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/*
* Copyright 2000-2018 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 back end data providers.
*
* @param <T>
* data provider data type
* @param <F>
* data provider filter type
* @since 8.0
*/
public abstract class AbstractBackEndDataProvider<T, F> extends
AbstractDataProvider<T, F> implements BackEndDataProvider<T, F> {
private List<QuerySortOrder> sortOrders = new ArrayList<>();
private Query<T, F> mixInSortOrders(Query<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 Query<>(query.getOffset(), query.getLimit(),
combinedSortOrders, query.getInMemorySorting(),
query.getFilter().orElse(null));
}
@Override
public Stream<T> fetch(Query<T, F> query) {
return fetchFromBackEnd(mixInSortOrders(query));
}
@Override
public int size(Query<T, F> query) {
return sizeInBackEnd(mixInSortOrders(query));
}
/**
* Fetches data from the back end using the given query.
*
* @param query
* the query that defines sorting, filtering and paging for
* fetching the data
* @return a stream of items matching the query
*/
protected abstract Stream<T> fetchFromBackEnd(Query<T, F> query);
/**
* Counts the number of items available in the back end.
*
* @param query
* the query that defines filtering to be used for counting the
* number of items
* @return the number of available items
*/
protected abstract int sizeInBackEnd(Query<T, F> query);
@Override
public void setSortOrders(List<QuerySortOrder> sortOrders) {
this.sortOrders = Objects.requireNonNull(sortOrders,
"Sort orders cannot be null");
refreshAll();
}
}
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