com.spotify.asyncdatastoreclient.QueryResult.java Source code

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Here is the source code for com.spotify.asyncdatastoreclient.QueryResult.java

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/*
 * Copyright (c) 2011-2015 Spotify AB
 *
 * 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.spotify.asyncdatastoreclient;

import com.google.api.services.datastore.DatastoreV1;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.protobuf.ByteString;

import java.util.Iterator;
import java.util.List;
import java.util.stream.Collectors;

/**
 * A query result.
 *
 * Returned from query operations.
 */
public final class QueryResult implements Result, Iterable<Entity> {

    private final List<Entity> entities;
    private final ByteString cursor;

    private QueryResult(final List<Entity> entities) {
        this.entities = entities;
        this.cursor = null;
    }

    private QueryResult(final List<Entity> entities, final ByteString cursor) {
        this.entities = entities;
        this.cursor = cursor;
    }

    static QueryResult build(final DatastoreV1.LookupResponse response) {
        return new QueryResult(ImmutableList.copyOf(response.getFoundList().stream()
                .map(entity -> Entity.builder(entity.getEntity()).build()).collect(Collectors.toList())));
    }

    static QueryResult build(final DatastoreV1.RunQueryResponse response) {
        final DatastoreV1.QueryResultBatch batch = response.getBatch();
        return new QueryResult(
                ImmutableList.copyOf(batch.getEntityResultList().stream()
                        .map(entity -> Entity.builder(entity.getEntity()).build()).collect(Collectors.toList())),
                batch.hasEndCursor() ? batch.getEndCursor() : null);
    }

    /**
     * Build an empty result.
     *
     * @return a new empty query result.
     */
    public static QueryResult build() {
        return new QueryResult(ImmutableList.of());
    }

    /**
     * Return the first entity returned from the query or null if not found.
     *
     * This is a shortcut for {@code getAll().get(0)}
     *
     * @return an entity returned from the Datastore.
     */
    public Entity getEntity() {
        return Iterables.getFirst(entities, null);
    }

    /**
     * Return all entities returned from the query.
     *
     * @return a list of entities returned from the query.
     */
    public List<Entity> getAll() {
        return entities;
    }

    /**
     * An iterator for all entities returned from the query.
     *
     * @return an entity iterator.
     */
    @Override
    public Iterator<Entity> iterator() {
        return entities.iterator();
    }

    /**
     * The last cursor position after returning all entities for this batch.
     *
     * This is useful for paging; if you supply a {@code limit()}, then the
     * cursor can be used when retrieving the next batch: {@code QueryfromCursor()}.
     *
     * @return the last cursor position.
     */
    public ByteString getCursor() {
        return cursor;
    }
}