com.google.appengine.api.datastore.ReadPolicy Maven / Gradle / Ivy

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API for Google App Engine standard environment with some of the dependencies shaded (repackaged)

There is a newer version: 2.0.27

/*
 * Copyright 2021 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
 *
 *     https://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.appengine.api.datastore;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Policy for reads.
 *
 */
public final class ReadPolicy {

  /**
   * Setting the {@code Consistency} for reads allows you to decide whether freshness or
   * availability is more important.
   */
  public enum Consistency {

    /**
     * Selects freshness over availability. Strongly consistent reads are guaranteed to return the
     * most up-to-date data but will timeout more often than eventually consistent reads.
     */
    STRONG,

    /**
     * Selects availability over freshness. Eventually consistent reads will timeout less often than
     * Strong reads but will occasionally return stale results.
     */
    EVENTUAL
  }

  private final Consistency consistency;

  public ReadPolicy(Consistency consistency) {
    if (consistency == null) {
      throw new NullPointerException("consistency must not be null");
    }
    this.consistency = consistency;
  }

  public Consistency getConsistency() {
    return consistency;
  }

  @Override
  public boolean equals(@Nullable Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }

    ReadPolicy that = (ReadPolicy) o;

    if (consistency != that.consistency) {
      return false;
    }

    return true;
  }

  @Override
  public int hashCode() {
    return consistency.hashCode();
  }
}