graphql.annotations.connection.PaginatedDataConnectionFetcher Maven / Gradle / Ivy
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/**
* Copyright 2016 Yurii Rashkovskii
*
* 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
*/
package graphql.annotations.connection;
import graphql.relay.*;
import graphql.schema.DataFetcher;
import graphql.schema.DataFetchingEnvironment;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
/**
* Use this class in {@link GraphQLConnection} to do a real pagination,
* i.e you fetch each time the relevant data, you make the cursors and
* you decide if there are previous or next pages
*
* Note: If you are using the connection, the return type of the associated dataFetcher must implement {@link PaginatedData}
*
* @param the entity type that is paginated
*/
public class PaginatedDataConnectionFetcher implements ConnectionFetcher {
private DataFetcher> paginationDataFetcher;
public PaginatedDataConnectionFetcher(DataFetcher> paginationDataFetcher) {
this.paginationDataFetcher = paginationDataFetcher;
}
@Override
public Connection get(DataFetchingEnvironment environment) throws Exception{
PaginatedData paginatedData = paginationDataFetcher.get(environment);
if (paginatedData == null) {
return new DefaultConnection<>(Collections.emptyList(), new DefaultPageInfo(null,null,false,false));
}
List> edges = buildEdges(paginatedData);
PageInfo pageInfo = getPageInfo(edges, paginatedData);
return new DefaultConnection<>(edges, pageInfo);
}
private PageInfo getPageInfo(List> edges, PaginatedData paginatedData) {
if (edges.isEmpty()) {
return new DefaultPageInfo(null,null,false,false);
}
ConnectionCursor firstCursor = edges.get(0).getCursor();
ConnectionCursor lastCursor = edges.get(edges.size() - 1).getCursor();
return new DefaultPageInfo(
firstCursor,
lastCursor,
paginatedData.hasPreviousPage(),
paginatedData.hasNextPage()
);
}
private List> buildEdges(PaginatedData paginatedData) {
Iterator data = paginatedData.iterator();
List> edges = new ArrayList<>();
for (; data.hasNext(); ) {
T entity = data.next();
edges.add(new DefaultEdge<>(entity, new DefaultConnectionCursor(paginatedData.getCursor(entity))));
}
return edges;
}
}