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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.Collection;
import java.util.Comparator;
import java.util.Objects;
import java.util.Optional;
import java.util.stream.Stream;
import com.vaadin.server.SerializableComparator;
import com.vaadin.server.SerializablePredicate;
/**
* {@link DataProvider} wrapper for {@link Collection}s.
*
* @param <T>
* data type
* @since 8.0
*/
public class ListDataProvider<T>
extends AbstractDataProvider<T, SerializablePredicate<T>>
implements InMemoryDataProvider<T> {
private SerializableComparator<T> sortOrder = null;
private SerializablePredicate<T> filter;
private final Collection<T> backend;
/**
* Constructs a new ListDataProvider.
* <p>
* No protective copy is made of the list, and changes in the provided
* backing Collection will be visible via this data provider. The caller
* should copy the list if necessary.
*
* @param items
* the initial data, not null
*/
public ListDataProvider(Collection<T> items) {
Objects.requireNonNull(items, "items cannot be null");
backend = items;
sortOrder = null;
}
/**
* Returns the underlying data items.
*
* @return the underlying data items
*/
public Collection<T> getItems() {
return backend;
}
@Override
public Stream<T> fetch(Query<T, SerializablePredicate<T>> query) {
Stream<T> stream = getFilteredStream(query);
Optional<Comparator<T>> comparing = Stream
.of(query.getInMemorySorting(), sortOrder)
.filter(c -> c != null)
.reduce((c1, c2) -> c1.thenComparing(c2));
if (comparing.isPresent()) {
stream = stream.sorted(comparing.get());
}
return stream.skip(query.getOffset()).limit(query.getLimit());
}
@Override
public int size(Query<T, SerializablePredicate<T>> query) {
return (int) getFilteredStream(query).count();
}
private Stream<T> getFilteredStream(
Query<T, SerializablePredicate<T>> query) {
Stream<T> stream = backend.stream();
// Apply our own filters first so that query filters never see the items
// that would already have been filtered out
if (filter != null) {
stream = stream.filter(filter);
}
stream = query.getFilter().map(stream::filter).orElse(stream);
return stream;
}
@Override
public SerializableComparator<T> getSortComparator() {
return sortOrder;
}
@Override
public void setSortComparator(SerializableComparator<T> comparator) {
this.sortOrder = comparator;
refreshAll();
}
@Override
public SerializablePredicate<T> getFilter() {
return filter;
}
@Override
public void setFilter(SerializablePredicate<T> filter) {
this.filter = filter;
refreshAll();
}
}
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