InterfaceStability.java

// Copyright 2016 Twitter. All rights reserved.
//
// 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.twitter.heron.classification;

import java.lang.annotation.Documented;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

/**
 * Annotation to inform users of how much to rely on a particular package,
 * class or method not changing over time. Currently the stability can be
 * {@link Stable}, {@link Evolving} or {@link Unstable}. <br>
 *
 * <ul><li>All classes that are annotated with {@link InterfaceAudience.Public} or
 * {@link InterfaceAudience.LimitedPrivate} must have InterfaceStability annotation. </li>
 * <li>Classes that are {@link InterfaceAudience.Private} are to be considered unstable unless
 * a different InterfaceStability annotation states otherwise.</li>
 * <li>Incompatible changes must not be made to classes marked as stable.</li>
 * </ul>
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public class InterfaceStability {

  /**
   * Can evolve while retaining compatibility for minor release boundaries.;
   * can break compatibility only at major release (ie. at m.0).
   */
  @Documented
  @Retention(RetentionPolicy.RUNTIME)
  @Inherited
  public @interface Stable { }

  /**
   * Evolving, but can break compatibility at minor release (i.e. m.x)
   */
  @Documented
  @Retention(RetentionPolicy.RUNTIME)
  @Inherited
  public @interface Evolving { }

  /**
   * No guarantee is provided as to reliability or stability across any
   * level of release granularity.
   */
  @Documented
  @Retention(RetentionPolicy.RUNTIME)
  @Inherited
  public @interface Unstable { }
}