1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the 7 * "License"); you may not use this file except in compliance 8 * with the License. You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 package org.apache.hadoop.hbase.classification; 19 20 import java.lang.annotation.Documented; 21 import java.lang.annotation.Retention; 22 import java.lang.annotation.RetentionPolicy; 23 24 /** 25 * Annotation to inform users of a package, class or method's intended audience. 26 * Currently the audience can be {@link Public}, {@link LimitedPrivate} or 27 * {@link Private}. <br> 28 * All public classes must have InterfaceAudience annotation. <br> 29 * <ul> 30 * <li>Public classes that are not marked with this annotation must be 31 * considered by default as {@link Private}.</li> 32 * 33 * <li>External applications must only use classes that are marked 34 * {@link Public}. Avoid using non public classes as these classes 35 * could be removed or change in incompatible ways.</li> 36 * 37 * <li>Hadoop projects must only use classes that are marked 38 * {@link LimitedPrivate} or {@link Public}</li> 39 * 40 * <li> Methods may have a different annotation that it is more restrictive 41 * compared to the audience classification of the class. Example: A class 42 * might be {@link Public}, but a method may be {@link LimitedPrivate} 43 * </li></ul> 44 */ 45 @InterfaceAudience.Public 46 @InterfaceStability.Evolving 47 public class InterfaceAudience { 48 /** 49 * Intended for use by any project or application. 50 */ 51 @Documented 52 @Retention(RetentionPolicy.RUNTIME) 53 public @interface Public {}; 54 55 /** 56 * Intended only for the project(s) specified in the annotation. 57 * For example, "Common", "HDFS", "MapReduce", "ZooKeeper", "HBase". 58 */ 59 @Documented 60 @Retention(RetentionPolicy.RUNTIME) 61 public @interface LimitedPrivate { value()62 String[] value(); 63 }; 64 65 /** 66 * Intended for use only within Hadoop itself. 67 */ 68 @Documented 69 @Retention(RetentionPolicy.RUNTIME) 70 public @interface Private {}; 71 InterfaceAudience()72 private InterfaceAudience() {} // Audience can't exist on its own 73 } 74