1 /* 2 * 3 * Licensed to the Apache Software Foundation (ASF) under one 4 * or more contributor license agreements. See the NOTICE file 5 * distributed with this work for additional information 6 * regarding copyright ownership. The ASF licenses this file 7 * to you under the Apache License, Version 2.0 (the 8 * "License"); you may not use this file except in compliance 9 * with the License. You may obtain a copy of the License at 10 * 11 * http://www.apache.org/licenses/LICENSE-2.0 12 * 13 * Unless required by applicable law or agreed to in writing, software 14 * distributed under the License is distributed on an "AS IS" BASIS, 15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 * See the License for the specific language governing permissions and 17 * limitations under the License. 18 */ 19 package org.apache.hadoop.hbase.util; 20 21 import org.apache.hadoop.classification.InterfaceAudience; 22 import org.apache.hadoop.classification.InterfaceStability; 23 24 /** 25 * Manages a singleton instance of the environment edge. This class shall 26 * implement static versions of the interface {@link EnvironmentEdge}, then 27 * defer to the delegate on invocation. 28 */ 29 @InterfaceAudience.Public 30 @InterfaceStability.Evolving 31 public class EnvironmentEdgeManager { 32 private static volatile EnvironmentEdge delegate = new DefaultEnvironmentEdge(); 33 34 private EnvironmentEdgeManager() { 35 36 } 37 38 /** 39 * Retrieves the singleton instance of the {@link EnvironmentEdge} that is 40 * being managed. 41 * 42 * @return the edge. 43 */ 44 public static EnvironmentEdge getDelegate() { 45 return delegate; 46 } 47 48 /** 49 * Resets the managed instance to the default instance: {@link 50 * DefaultEnvironmentEdge}. 51 */ 52 public static void reset() { 53 injectEdge(new DefaultEnvironmentEdge()); 54 } 55 56 /** 57 * Injects the given edge such that it becomes the managed entity. If null is 58 * passed to this method, the default type is assigned to the delegate. 59 * 60 * @param edge the new edge. 61 */ 62 public static void injectEdge(EnvironmentEdge edge) { 63 if (edge == null) { 64 reset(); 65 } else { 66 delegate = edge; 67 } 68 } 69 70 /** 71 * Defers to the delegate and calls the 72 * {@link EnvironmentEdge#currentTimeMillis()} method. 73 * 74 * @return current time in millis according to the delegate. 75 */ 76 public static long currentTimeMillis() { 77 return getDelegate().currentTimeMillis(); 78 } 79 }