com.google.cloud.datastore.ReadOption.java Source code

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Here is the source code for com.google.cloud.datastore.ReadOption.java

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/*
 * Copyright 2016 Google LLC
 *
 * 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.google.cloud.datastore;

import com.google.common.collect.ImmutableMap;

import java.io.Serializable;
import java.util.Map;

/**
 * Specifies options for read operations in Datastore, namely getting/fetching entities and running
 * queries.
 */
public abstract class ReadOption implements Serializable {

    private static final long serialVersionUID = -4406964829189800528L;

    /**
     * Specifies eventual consistency for reads from Datastore. Lookups and ancestor queries using
     * this option permit Datastore to return stale results.
     */
    public static final class EventualConsistency extends ReadOption {

        private static final long serialVersionUID = -6959530217724666172L;

        private final boolean eventualConsistency;

        private EventualConsistency(boolean eventualConsistency) {
            this.eventualConsistency = eventualConsistency;
        }

        public boolean isEventual() {
            return eventualConsistency;
        }
    }

    private ReadOption() {
    }

    /**
     * Returns a {@code ReadOption} that specifies eventual consistency, allowing Datastore to return
     * stale results from gets, fetches, and ancestor queries.
     */
    public static EventualConsistency eventualConsistency() {
        return new EventualConsistency(true);
    }

    static Map<Class<? extends ReadOption>, ReadOption> asImmutableMap(ReadOption... options) {
        ImmutableMap.Builder<Class<? extends ReadOption>, ReadOption> builder = ImmutableMap.builder();
        for (ReadOption option : options) {
            builder.put(option.getClass(), option);
        }
        return builder.build();
    }
}