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 23 /** 24 * Manages a singleton instance of the environment edge. This class shall 25 * implement static versions of the interface {@link EnvironmentEdge}, then 26 * defer to the delegate on invocation. 27 */ 28 @InterfaceAudience.Private 29 public class EnvironmentEdgeManager { 30 private static volatile EnvironmentEdge delegate = new DefaultEnvironmentEdge(); 31 32 private EnvironmentEdgeManager() { 33 34 } 35 36 /** 37 * Retrieves the singleton instance of the {@link EnvironmentEdge} that is 38 * being managed. 39 * 40 * @return the edge. 41 */ 42 public static EnvironmentEdge getDelegate() { 43 return delegate; 44 } 45 46 /** 47 * Resets the managed instance to the default instance: {@link 48 * DefaultEnvironmentEdge}. 49 */ 50 public static void reset() { 51 injectEdge(new DefaultEnvironmentEdge()); 52 } 53 54 /** 55 * Injects the given edge such that it becomes the managed entity. If null is 56 * passed to this method, the default type is assigned to the delegate. 57 * 58 * @param edge the new edge. 59 */ 60 public static void injectEdge(EnvironmentEdge edge) { 61 if (edge == null) { 62 reset(); 63 } else { 64 delegate = edge; 65 } 66 } 67 68 /** 69 * Defers to the delegate and calls the 70 * {@link EnvironmentEdge#currentTimeMillis()} method. 71 * 72 * @return current time in millis according to the delegate. 73 */ 74 public static long currentTimeMillis() { 75 return getDelegate().currentTimeMillis(); 76 } 77 }