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/*
* Copyright 2000-2016 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.stream.Stream;
/**
* A common interface for fetching hierarchical data from a data source, such as
* an in-memory collection or a backend database.
*
* @author Vaadin Ltd
* @since 8.1
*
* @param <T>
* data type
* @param <F>
* filter type
*/
public interface HierarchicalDataProvider<T, F> extends DataProvider<T, F> {
/**
* Get the number of immediate child data items for the parent item returned
* by a given query.
*
* @param query
* given query to request the count for
* @return the count of child data items for the data item
* {@link HierarchicalQuery#getParent()}
*
* @throws IllegalArgumentException
* if the query is not of type HierarchicalQuery
*/
@Override
public default int size(Query<T, F> query) {
if (query instanceof HierarchicalQuery<?, ?>) {
return getChildCount((HierarchicalQuery<T, F>) query);
}
throw new IllegalArgumentException(
"Hierarchical data provider doesn't support non-hierarchical queries");
}
/**
* Fetches data from this HierarchicalDataProvider using given
* {@code query}. Only the immediate children of
* {@link HierarchicalQuery#getParent()} will be returned.
*
* @param query
* given query to request data with
* @return a stream of data objects resulting from the query
*
* @throws IllegalArgumentException
* if the query is not of type HierarchicalQuery
*/
@Override
public default Stream<T> fetch(Query<T, F> query) {
if (query instanceof HierarchicalQuery<?, ?>) {
return fetchChildren((HierarchicalQuery<T, F>) query);
}
throw new IllegalArgumentException(
"Hierarchical data provider doesn't support non-hierarchical queries");
}
/**
* Get the number of immediate child data items for the parent item returned
* by a given query.
*
* @param query
* given query to request the count for
* @return the count of child data items for the data item
* {@link HierarchicalQuery#getParent()}
*/
public int getChildCount(HierarchicalQuery<T, F> query);
/**
* Fetches data from this HierarchicalDataProvider using given
* {@code query}. Only the immediate children of
* {@link HierarchicalQuery#getParent()} will be returned.
*
* @param query
* given query to request data with
* @return a stream of data objects resulting from the query
*/
public Stream<T> fetchChildren(HierarchicalQuery<T, F> query);
/**
* Check whether a given item has any children associated with it.
*
* @param item
* the item to check for children
* @return whether the given item has children
*/
public boolean hasChildren(T item);
}
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