001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.metrics2;
020
021import com.google.common.base.Objects;
022import static com.google.common.base.Preconditions.*;
023
024import org.apache.hadoop.classification.InterfaceAudience;
025import org.apache.hadoop.classification.InterfaceStability;
026
027/**
028 * The immutable metric
029 */
030@InterfaceAudience.Public
031@InterfaceStability.Evolving
032public abstract class AbstractMetric implements MetricsInfo {
033  private final MetricsInfo info;
034
035  /**
036   * Construct the metric
037   * @param info  about the metric
038   */
039  protected AbstractMetric(MetricsInfo info) {
040    this.info = checkNotNull(info, "metric info");
041  }
042
043  @Override public String name() {
044    return info.name();
045  }
046
047  @Override public String description() {
048    return info.description();
049  }
050
051  protected MetricsInfo info() {
052    return info;
053  }
054
055  /**
056   * Get the value of the metric
057   * @return the value of the metric
058   */
059  public abstract Number value();
060
061  /**
062   * Get the type of the metric
063   * @return the type of the metric
064   */
065  public abstract MetricType type();
066
067  /**
068   * Accept a visitor interface
069   * @param visitor of the metric
070   */
071  public abstract void visit(MetricsVisitor visitor);
072
073  @Override public boolean equals(Object obj) {
074    if (obj instanceof AbstractMetric) {
075      final AbstractMetric other = (AbstractMetric) obj;
076      return Objects.equal(info, other.info()) &&
077             Objects.equal(value(), other.value());
078    }
079    return false;
080  }
081
082  @Override public int hashCode() {
083    return Objects.hashCode(info, value());
084  }
085
086  @Override public String toString() {
087    return Objects.toStringHelper(this)
088        .add("info", info)
089        .add("value", value())
090        .toString();
091  }
092}