BasicTag.java

/*
 * Copyright 2014 Netflix, Inc.
 *
 * 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.netflix.servo.tag;

import com.netflix.servo.util.Preconditions;

/**
 * Immutable tag.
 */
public final class BasicTag implements Tag {

  private final String key;
  private final String value;

  /**
   * Creates a new instance with the specified key and value.
   */
  public BasicTag(String key, String value) {
    this.key = checkNotEmpty(key, "key");
    this.value = checkNotEmpty(value, "value");
  }

  /**
   * Verify that the {@code v} is not null or an empty string.
   */
  private static String checkNotEmpty(String v, String name) {
    Preconditions.checkNotNull(v, name);
    Preconditions.checkArgument(!v.isEmpty(), "%s cannot be empty", name);
    return v;
  }

  /**
   * {@inheritDoc}
   */
  public String getKey() {
    return key;
  }

  /**
   * {@inheritDoc}
   */
  public String getValue() {
    return value;
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    } else if (o instanceof Tag) {
      Tag t = (Tag) o;
      return key.equals(t.getKey()) && value.equals(t.getValue());
    } else {
      return false;
    }
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public int hashCode() {
    int result = key.hashCode();
    result = 31 * result + value.hashCode();
    return result;
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public String toString() {
    return key + "=" + value;
  }

  /**
   * Parse a string representing a tag. A tag string should have the format {@code key=value}.
   * Whitespace at the ends of the key and value will be removed. Both the key and value must
   * have at least one character.
   *
   * @param tagString string with encoded tag
   * @return tag parsed from the string
   * @deprecated Use Tags.parseTag instead.
   */
  public static BasicTag parseTag(String tagString) {
    return (BasicTag) Tags.parseTag(tagString);
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public String tagString() {
    return toString();
  }
}