hadoop-hdds/common/src/main/java/org/apache/hadoop/hdds/utils/db/cache/CacheResult.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * 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 org.apache.hadoop.hdds.utils.db.cache;

import java.util.Objects;

/**
 * CacheResult which is returned as response for Key exist in cache or not.
 * @param <CACHEVALUE>
 */
public class CacheResult<CACHEVALUE extends CacheValue> {

  private CacheStatus cacheStatus;
  private CACHEVALUE cachevalue;

  public CacheResult(CacheStatus cacheStatus, CACHEVALUE cachevalue) {
    this.cacheStatus = cacheStatus;
    this.cachevalue = cachevalue;
  }

  public CacheStatus getCacheStatus() {
    return cacheStatus;
  }

  public CACHEVALUE getValue() {
    return cachevalue;
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }
    CacheResult< ? > that = (CacheResult< ? >) o;
    return cacheStatus == that.cacheStatus &&
        Objects.equals(cachevalue, that.cachevalue);
  }

  @Override
  public int hashCode() {
    return Objects.hash(cacheStatus, cachevalue);
  }

  /**
   * Status which tells whether key exists in cache or not.
   */
  public enum CacheStatus {
    EXISTS, // When key exists in cache.

    NOT_EXIST, // We guarantee that it does not exist. This will be returned
    // when the key does not exist in cache, when cache clean up policy is
    // NEVER.
    MAY_EXIST  // This will be returned when the key does not exist in
    // cache, when cache clean up policy is MANUAL. So caller need to check
    // if it might exist in it's rocksdb table.
  }
}